Ebook Diagnostic imaging gastrointestinal: Part 2

SECTION 8

Spleen

Introduction and Overview
Imaging Approach to the Spleen

544

Normal Variants and Artifacts
Accessory Spleen

548

Congenital
Asplenia and Polysplenia

550

Infection
Splenic Infection and Abscess

554

Degenerative
Splenomegaly and Hypersplenism

558

Vascular Disorders
Splenic Infarction

562

Trauma
Splenic Trauma

566

Splenosis

570

Benign Neoplasms
Splenic Cyst

572

Primary Splenic Tumors

574

Malignant Neoplasms
Splenic Metastases and Lymphoma

578


Spleen

Imaging Approach to the Spleen

Embryology, Anatomy, and Physiology
The spleen develops from the dorsal mesogastrium and
usually rotates to the left, becoming fixed in the left
subphrenic location by peritoneal reflections linking it to the
diaphragm, abdominal wall, stomach (gastrosplenic ligament),
and kidney (splenorenal ligament). It usually develops as 1
"fused" mass of tissue, but variations are common.
One or more accessory spleens are found in up to 30% of the
general population, usually small spherical structures near the
splenic hilum. These can enlarge, especially following
splenectomy, and may simulate a neoplastic mass or cause
recurrence of hematologic disease.
The spleen may be congenitally absent (asplenia) or have
many unfused components (polysplenia). These are rare
splenic anomalies and are associated with cardiovascular
anomalies, situs inversus, and other anomalies, often with
serious and even life-threatening consequences.
The spleen is rarely on a long mesentery and may be found in
any abdominal or pelvic location ("wandering spleen"), placing
it at risk for trauma and torsion with infarction.
The spleen is the largest lymphatic organ, the size of which
varies among individuals and even in the same person by
blood volume, state of nutrition and hydration. The usual
volume range is 100-250 cm³, with a mean of 150 cm³. A
calculated splenic index (length x width x breadth) over 480
cm³ is considered splenomegaly. The average length is up to
12 cm, with a width and breadth of 7 and 4 cm, respectively.

Imaging Issues
The spleen has a unique histology, consisting of the red and

white pulp, which directly affects its appearance on imaging
exams. The white pulp is the lymphoid tissue and the red is
composed of the vascular tissue and splenic cords (plates of
cells and sinusoids). Because of its vascularity, the red pulp
enhances rapidly, giving the spleen a very heterogeneous
pattern of enhancement on arterial phase enhanced CT or MR
imaging. This may be mistaken for splenic pathology but is a
transient phenomenon not evident on unenhanced or later
phases of enhanced imaging.
CT is the imaging modality of choice for the evaluation of the
spleen in the acute setting (trauma or pain). MR can be
additive in evaluating splenic masses and some metabolic
diseases (e.g., hemochromatosis). The spleen has a relatively
long T1 and T2 relaxation time. This results in its appearing
somewhat hypointense compared to the liver on T1WI and
hyperintense on T2WI. With iron deposition, the spleen may
show a dramatic loss in signal.

Approach to the Abnormal Spleen
Splenomegaly is a very common finding and may result from
numerous causes, usually grouped into 5 general etiologies,
including congestion, hematologic, inflammatory-infectious ,
tumor, or infiltrative.
Given its function as a blood filter, it is not surprising that the
spleen is a frequent site of metastases on postmortem
examination of patients who have died from cancer. However,
with the exception of leukemia and lymphoma, it is
uncommon to make an imaging diagnosis of splenic
metastasis.

544

Many splenic neoplasms are benign, either hemangiomas or
lymphangiomas, but these have overlapping imaging features
and a specific diagnosis is rarely possible.
One of the most common focal splenic lesions is the splenic
cyst. It is not possible to distinguish the primary congenital
(epithelial-lined) cyst from the acquired cyst by imaging, with
the latter resulting from prior infarction, infection, or trauma.
These are rarely of clinical importance.
Multiple lesions within the spleen are most typically the result
of a granulomatous process, which may be either infectious
(e.g., histoplasmosis, TB) or noninfectious (sarcoidosis). Splenic
granulomata commonly calcify.
The pancreatic tail usually inserts into the splenic hilum
through the splenorenal ligament. Inflammatory or neoplastic
conditions affecting the pancreatic tail can easily invade the
splenic parenchyma, resulting in intrasplenic pseudocyst, for
instance. Conversely, splenic tumors or an accessory spleen
may mimic a pancreatic tail mass.
Splenic infarction is a relatively common cause of acute left
upper quadrant pain. It appears as a sharply defined, often
wedge-shaped zone of minimal enhancement abutting the
splenic capsule. Patients at risk for infarction include those
with sickle cell disease and those with cardiovascular
conditions, such as atrial fibrillation. Patients with left
ventricular assist devices are especially prone to embolic
infarction of the spleen.
The spleen is often injured in blunt and penetrating trauma.
Most children and adults with splenic lacerations will recover

without surgery, but the presence of active extravasation
(evident on CT) or clinical instability may demand intervention,
either surgery or transcatheter embolization.
Splenosis is the peritoneal implantation of splenic tissue that
may follow traumatic rupture of the spleen. This may be
mistaken for polysplenia or peritoneal implants of tumor
(carcinomatosis). The history of trauma, absence of a normal
spleen, and enhancement characteristics identical to spleen
usually allow accurate diagnosis.

Differential Diagnosis
Splenomegaly
Common
• Cirrhosis with portal hypertension
• Congestive heart failure
• AIDS
• Splenic metastases and lymphoma
• Hemoglobinopathies
• Leukemia
• Sarcoidosis
• Mononucleosis
• Myeloproliferative disorders
• Splenic trauma
Less common
• Splenic tumors (primary)
• Systemic infection and abscesses
• Splenic vein occlusion
• Splenic infarction
• Malaria
• Collagen vascular diseases: Rheumatoid arthritis,

scleroderma, dermatomyositis, polyarteritis nodosa
• Storage diseases: Amyloidosis, glycogen storage disease
• Peliosis


Imaging Approach to the Spleen

Less common
• Echinococcal (hydatid) cyst
• Healed abscess
Solid Splenic Mass or Masses
Common
• Splenic trauma
• Splenic infarction
• Splenic metastases and lymphoma
• Perfusion artifact
Less common
• Sarcoidosis
• Splenic infection and abscess
• Splenic tumors

• Peliosis
Cystic Splenic Mass
Common
• Acquired or congenital splenic cyst
• Splenic trauma
• Splenic infarction

Spleen

Multiple Splenic Calcifications
Common
• Histoplasmosis
• Tuberculosis
• Arterial calcification and aneurysm
• Pneumocystis jiroveci
• Splenic infarction
• Splenic cyst

Less common
• Splenic metastases and lymphoma
• Splenic infection and abscess
• Splenic tumors
• Pancreatic pseudocyst
Diffuse Increased Attenuation, Spleen
Common
• Hemochromatosis
• Splenic infarction: Sickle cell anemia
Less common
• Opportunistic infection
• Thorotrast

(Left) Arterial phase axial
CECT shows a very
heterogeneous spleen caused
by rapid enhancement of the
vascular sinusoids (red pulp).
This should not be mistaken
for a pathologic process.
(Right) Axial CECT during the

venous phase shows the
spleen with a homogeneous
appearance.

(Left) Axial T1WI MR (A) shows
the normal spleen ſt as
slightly hypointense relative to
liver. On T2WI MR (B), the
normal spleen is slightly
hyperintense to liver. (Right)
Axial CECT shows a "mass" ſt
in the pancreatic tail that is
isodense to the spleen and
represents an accessory
spleen. This could be mistaken
for a primary pancreatic mass,
such as a neuroendocrine
tumor.

545


Spleen

Imaging Approach to the Spleen

Gastric impression

Stomach
Renal impression

Prominent medial lobulation

Kidney

Stomach

Gastrosplenic ligament

Spleen
Splenic artery

Splenorenal ligament
Splenic vein
Splenocolic ligament

(Top) Graphic shows the medial surface of the spleen and representative axial sections at 3 different levels. The spleen is of variable
shape and size, even within the same individual, varying with states of nutrition and hydration. The medial surface is often quite
lobulated as it is interposed between the stomach and the kidney. (Bottom) The splenic artery and vein course along the body of the
pancreas, entering and exiting the spleen via the splenorenal ligament. The tail of the pancreas also inserts into the splenic hilum
through the splenorenal ligament. The gastrosplenic ligament carries the short gastric and left gastroepiploic vessels to the stomach
and upper portion of the spleen.

546


Imaging Approach to the Spleen
Spleen

(Left) Axial CECT in a patient

with non-Hodgkin lymphoma
shows numerous enlarged
upper abdominal lymph nodes
ſt. Splenomegaly is a
common abnormality and can
be caused by congestion,
hematologic disorders,
inflammatory/infectious
conditions, tumors, or
infiltrative processes. (Right)
Axial CECT in a different case
of splenomegaly caused by
congestion secondary to
cirrhosis and portal
hypertension shows the
recanalized umbilical vein ſt.

(Left) Axial CECT shows 2
splenic lesions. The larger
lesion ﬈ has water density
contents and thin, sharp walls,
typical of simple cyst. The
smaller lesion ﬊ has nodular
walls and higher density
contents, suggestive of splenic
lymphangioma. (Right) In this
patient with non-Hodgkin
lymphoma the spleen is
markedly enlarged with
heterogeneous,

hypoattenuating, more
discrete tumor foci ﬈.
Lymphomatous infiltration is
also present within the
adrenal gland ﬉ and nodes
﬇ throughout the abdomen.

(Left) Axial CECT in a patient
with heart failure and
abdominal pain shows a
ventricular assist device st
and wedge-shaped regions of
nonenhancing splenic
parenchyma ſt that extend to
the capsular surface,
characteristic of acute splenic
infarctions. (Right) Axial CECT
in a patient injured in a motor
vehicle crash shows a sentinel
clot st adjacent to the spleen
and a large hemoperitoneum
﬇. Note the active
extravasation of blood ſt that
is isodense to enhanced
vessels.

547


Spleen

Accessory Spleen
KEY FACTS

TERMINOLOGY
• Benign ectopic splenic tissue of congenital origin

IMAGING
• Most splenules located in or near splenic hilum or ligaments
○ 20% are near or within pancreatic tail and can mimic
pancreatic neuroendocrine tumor
○ May also be in diaphragmatic, pararenal, and gastric sites
• NECT and CECT: Same enhancement and attenuation as
normal spleen
○ Isodense to main spleen on noncontrast images
○ Characteristic serpiginous enhancement on arterial
phase
○ Homogeneous enhancement on venous/delayed images
• MR: T1WI hypointense and T2WI hyperintense
○ Follows appearance of spleen on all sequences
○ DWI: Isointense to spleen with similar ADC values
• Nuclear medicine: Technetium (Tc-99m) sulfur colloid or Tc99m heat-damaged red blood cell (RBC) scan

(Left) Axial CECT shows a
small spherical accessory
spleen ſt near the splenic
hilum. Note the foci of
calcification from
histoplasmosis in the main and
accessory spleen. This

appearance is so characteristic
as to require no additional
evaluation. (Right) Axial CECT
demonstrates a large mass ſt
abutting the pancreatic tail
and the splenic hilum. The
mass was thought to be a
neuroendocrine tumor and
was resected. Note that the
mass is isodense to the spleen.
The mass was found to be a
splenule at surgery.

(Left) Axial CECT shows an
enlarged spleen due to portal
hypertension in this patient
with cirrhosis. Note the
prominent accessory spleen ſt
as well as the varices ﬇. An
accessory spleen may enlarge
in parallel with the main
spleen. (Right) Axial CECT
shows a hypervascular mass
ſt within the pancreatic tail
that mimics an islet cell tumor.
A heat-damaged red blood cell
scan (not shown) proved this
to be an accessory spleen.
Masses in the splenic hilum
may arise from or involve the

tail of the pancreas or spleen.

548

○ Functional uptake in splenic tissue differentiates
splenule from other masses
• Rare complication: Torsion of splenule as cause of
abdominal pain in children or young adults

TOP DIFFERENTIAL DIAGNOSES
•
•
•
•
•

Splenosis
Polysplenia
Peritoneal metastases and lymphoma
Visceral mass (especially pancreatic neuroendocrine tumor)
Splenic artery aneurysm or pseudoaneurysm

PATHOLOGY
• Congenital: Failure of some embryonic splenic buds to unite
within dorsal mesogastrium

CLINICAL ISSUES
• Asymptomatic (vast majority of cases)
• In absence of complications (which are extraordinarily rare),
no treatment or intervention

Accessory Spleen

Synonyms
• Splenule, splenunculus

DIFFERENTIAL DIAGNOSIS

Definitions

Splenosis

• Benign ectopic splenic tissue of congenital origin

• Usually result of trauma; portions of disrupted spleen
implant anywhere including abdomen, pelvis, and chest

IMAGING
General Features
• Best diagnostic clue
○ Small, round, well-marginated nodule in left upper
quadrant with same enhancement as normal spleen
• Location
○ In or near splenic hilum or ligaments (most cases)
– 20% are near or within pancreatic tail
– Usually left upper quadrant, above renal pedicle
– Rarely in diaphragmatic, pararenal, and gastric sites
○ Single splenule in vast majority of patients
– 1 splenule (88%), 2 splenules (9%), > 2 splenules (3%)

– Multiple splenules usually clustered in 1 location
• Size
○ Varies from 1 mm to a few cm, usually < 2.5 cm

CT Findings
• Same enhancement as normal spleen
○ Isodense to main spleen on noncontrast images
○ Serpiginous enhancement on arterial phase
○ Homogeneous enhancement on venous/delayed images
• Most commonly located near splenic hilum or ligaments
• 2nd most common location is pancreatic tail
○ Usually < 3 cm medial to pancreatic tail
○ Most often along dorsal surface of pancreas
○ Incompletely surrounded by pancreatic parenchyma
• Rare: Torsion of splenule as cause of abdominal pain
○ Nonenhancing mass with surrounding hemorrhage
○ Whorl sign (twisted vascular pedicle) leading to splenule

MR Findings
• T1WI hypointense and T2WI hyperintense
○ Follows appearance of spleen on all sequences
• DWI: Isointense to spleen with similar apparent diffusion
coefficient (ADC) values
○ Pancreatic neuroendocrine tumors usually hyperintense
on DWI with lower ADC values
• Superparamagnetic iron oxide particles (SPIO) contrast
media taken up by splenic tissue (but not tumor)

Nuclear Medicine Findings
• Technetium (Tc-99m) sulfur colloid or Tc-99m heatdamaged red blood cell (RBC) scan

○ Functional uptake in splenic tissue differentiates
splenule from other masses
○ Tc-99m heat-damaged RBC scan preferred due to higher
specificity and better target to background
• PET CT
○ FDG-avid mass can mimic tumor

Imaging Recommendations

Spleen

○ Multiphase CT followed by Tc-99m heat-damaged RBC
scan in equivocal cases

TERMINOLOGY

Polysplenia
• Congenital disorder with multiple small spleens, bilateral
left-sidedness of viscera, and cardiovascular anomalies

Peritoneal Metastases and Lymphoma
• e.g., omental or peritoneal metastases

Visceral Mass
• Splenules commonly mistaken for pancreatic
neuroendocrine tumors
• Splenules also mistaken for adrenal, gastric, or renal tumors

Splenic Artery Aneurysm or Pseudoaneurysm
• Bright homogeneous enhancement on arterial phase

PATHOLOGY
General Features
• Etiology
○ Congenital: Failure of some embryonic splenic buds to
unite within dorsal mesogastrium

Gross Pathologic & Surgical Features
• Structurally normal splenic tissue

CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Asymptomatic (vast majority of cases)
• Other signs/symptoms
○ May torse, rupture, and bleed (very rare)
○ May cause recurrence of hematologic disease (e.g.,
lymphoma) following prior splenectomy

Demographics
• Epidemiology
○ Incidence: 10-30% of patients at autopsy

Treatment
• In absence of complications (which are extraordinarily rare),
no treatment or intervention
• Surgical resection: Only in setting of complications,
recurrence of lymphoma, or hypersplenism

DIAGNOSTIC CHECKLIST

Consider
• Accessory spleen is common and can be mistaken for tumor

SELECTED REFERENCES
1.

Coquia SF et al: Intrapancreatic accessory spleen: possibilities of computed
tomography in differentiation from nonfunctioning pancreatic
neuroendocrine tumor. J Comput Assist Tomogr. ePub, 2014

• Best imaging tool
549


Spleen

Asplenia and Polysplenia
KEY FACTS

TERMINOLOGY
• Complex inherited syndromes associated with absence or
multiplicity of spleens as well as many other anomalies

IMAGING
• Asplenia (ASP) syndrome: Right isomerism or bilateral
right-sidedness
○ Absent spleen in virtually all patients
○ Congenital heart disease in ~ 100% of patients
○ Bilateral trilobed lungs
○ Malrotation in most patients

○ Aorta and inferior vena cava (IVC) are frequently
ipsilateral (usually right side)
• Polysplenia (PSP) syndrome: Left isomerism or bilateral
left-sidedness
○ Usually multiple spleens, but may have single normal
spleen
○ Increased risk of complex cardiac anomalies, although
less common with PSP than ASP

(Left) Coronal volumerendered CECT in a patient
with polysplenia (PSP)
syndrome demonstrates
multiple spleens st in the left
upper quadrant. The multiple
spleens in PSP are typically in
the left abdomen, but can
rarely be on the right. (Right)
Axial CECT in the same patient
demonstrates a markedly
dilated azygous vein ﬇.

(Left) Axial CECT in the same
patient again demonstrates
multiple spleens st and a
dilated azygous vein ſt to the
right of the aorta. Azygous
continuation of the inferior
vena cava (IVC) is a very
common abnormality in PSP
syndrome. (Right) Axial CECT

in the same patient
demonstrates malrotation of
the bowel, with the small
bowel abnormally located in
the right abdomen and the
entirety of the colon in the left
abdomen. Malrotation is quite
common with both asplenia
(ASP) and PSP syndromes.

550

○ IVC interruption with azygos continuation very common
○ Bilateral bilobed lungs
○ Truncated/short pancreas or agenesis of dorsal pancreas
– Increased incidence of diabetes and pancreatitis
○ Intestinal malrotation is seen in most patients
○ Liver often midline with range of biliary abnormalities
○ Aorta usually located to left of midline

TOP DIFFERENTIAL DIAGNOSES
• Splenosis
• Accessory spleen
• Splenectomy

CLINICAL ISSUES
• ASP: Newborn or infant presentation due to cardiac disease
with poor prognosis and early mortality
○ ↑ risk of sepsis due to lack of spleen
• PSP: Infant or adult presentation with better prognosis due

to lesser incidence of cardiac disease


Asplenia and Polysplenia

Abbreviations
• Asplenia (ASP), polysplenia (PSP)

Synonyms
• Heterotaxy syndromes
• ASP: Asplenia syndrome, Ivemark syndrome, bilateral rightsidedness
• PSP: Polysplenia syndrome, bilateral left-sidedness

Definitions
• Complex inherited syndromes associated with absence
(ASP) or multiplicity (PSP) of spleens, as well as many other
anomalies

Associated Syndromes
• Heterotaxy: Abnormal embryologic placement of
thoracoabdominal structures across right-left axis of body
• Situs solitus: Normal placement of thoracoabdominal
organs in right-left axis
• Situs inversus: Reversal of normal positions of
thoracoabdominal organs across right-left axis (mirrorimage of situs solitus)
• Situs ambiguus (heterotaxy syndrome): Abnormal
placement of thoracoabdominal structures without situs
inversus

IMAGING

General Features
• Best diagnostic clue
○ ASP: Absence of spleen, abdominal aorta and inferior
vena cava (IVC) on same side (usually right), and bilateral
distribution of right-sided viscera
○ PSP: Multiple small spleens, intrahepatic interruption of
IVC with continuation of azygos vein, bilateral
distribution of left-sided viscera
• PSP
○ Number of spleens varies from 2 to 16
• Key concepts
○ ASP syndrome: Right isomerism or bilateral rightsidedness
– Situs ambiguus and bilateral right-sidedness; no fixed
set of findings, abnormalities exist across a spectrum
– Spleen
□ Absent spleen in virtually all patients
– Cardiovascular
□ Congenital heart disease in ~ 100% of patients
□ Total anomalous pulmonary venous return (almost
100%), endocardial cushion defect (85%), single
ventricle (51%), transposition of great vessels
(58%), pulmonary stenosis or atresia (70%),
dextrocardia (42%), mesocardia, ventricular septal
defect, single atrioventricular valve, bilateral
superior vena cava (SVC)
□ Aorta and IVC are frequently ipsilateral (usually
right side)
– Pulmonary
□ Abnormal distribution of lobes with bilateral
trilobed lungs

– Gastrointestinal

□ Malrotation in most patients with ASP
□ Other associations: Imperforate anus, ectopic liver,
annular pancreas, esophageal varices, gallbladder
agenesis, Hirschsprung disease, and duplication or
hypoplasia of stomach
– Genitourinary
□ Horseshoe kidney, bilobed urinary bladder,
hydroureter, double collecting system, cystic kidney
– Miscellaneous
□ Cleft palate, cleft lip, fused or horseshoe adrenal
gland, absent left adrenal gland, scoliosis,
bicornuate uterus, single umbilical artery, lumbar
myelomeningocele
○ PSP syndrome: Left isomerism or bilateral left-sidedness
– Situs ambiguus and bilateral left-sidedness: No fixed
set of findings and abnormalities exist across a
spectrum
– Spleen
□ Usually multiple spleens in left upper quadrant, but
some cases may have single normal spleen
□ Isolated reversal of splenic position (in right
abdomen) common
– Cardiovascular
□ Increased risk of complex cardiac anomalies,
although less common with PSP than with ASP,
accounting for better long-term survival
□ Transposition of great vessels (13%), double outlet
right ventricle (13%), pulmonary valvular stenosis

(23%), subaortic stenosis, or atresia
□ IVC interruption with azygos vein continuation is
2nd most common abnormality (65%) after
multiple spleens
□ Aorta usually located to left of midline
– Pulmonary
□ Abnormal distribution of lobes with bilateral
bilobed lungs
□ Only seen in 55% of patients
– Gastrointestinal
□ Truncated/short pancreas or agenesis of dorsal
pancreas with increased incidence of diabetes and
pancreatitis
□ Intestinal malrotation seen in most patients with
PSP and may range from nonrotation to complete
malrotation
□ Liver often midline with range of biliary tree
abnormalities (absent gallbladder, biliary atresia)
□ Isolated reversal of stomach position common
□ Other associations: Esophageal or duodenal atresia,
tracheoesophageal fistula, semiannular pancreas,
gastric duplication, short bowel
– Genitourinary
□ Renal agenesis, renal and ovarian cysts

Spleen

TERMINOLOGY

Radiographic Findings

• Radiography
○ ASP
– Heart: Mesocardia or dextrocardia
– Right-sided bronchial pattern and minor fissure may
be seen bilaterally
– Superior mediastinal widening (due to bilateral SVC)
551


Spleen

Asplenia and Polysplenia
– Both pulmonary arteries anterior to trachea on lateral
chest film
○ PSP
– Frontal view: Paratracheal soft tissue prominence
(dilated azygos/hemiazygos) mimicking mass
– Chest lateral view: Both pulmonary arteries posterior
to trachea and absence of IVC shadow

CT Findings
• ASP
○ Absence of spleen
○ Situs abnormalities: Liver, gallbladder, stomach, bowel,
heart, trilobed lungs
○ IVC and abdominal aorta lie on same side of spine
(usually on right side with aorta lying posteriorly)
• PSP
○ Multiple splenules in right or left upper quadrants
– ± asymmetric liver and midgut malrotation

○ Enlarged azygos or hemiazygos vein with azygous
continuation of IVC
– Absence of IVC between renal and hepatic veins with
independent drainage of hepatic veins into right
atrium

Imaging Recommendations
• Best imaging tool
○ CECT or MR can demonstrate position and number of
spleen(s), as well as other visceral organ abnormalities
associated with heterotaxy syndromes

DIFFERENTIAL DIAGNOSIS
Splenosis
• Scattered splenic tissue throughout abdomen usually seen
in setting of traumatic splenectomy
• Multiple small implants ranging in size from few mm to few
cm; should enhance similarly to normal splenic tissue
• No other associated anomalies

Accessory Spleen
• Normal embryologic variant usually found near splenic
hilum along course of splenic vessels
• Identical to normal splenic tissue on any phase of
enhancement
• No other associated anomalies

Splenectomy
• No splenic visualization after surgical splenectomy
• No other associated anomalies

PATHOLOGY
General Features
• Etiology
○ Uncertain etiology, but may be associated with gene
mutations (CFC1 gene, SHROOM3 gene, etc.)
– Altered timing in development of embryonic body
curvature leads to visceroatrial situs abnormalities
□ ASP: Delayed embryonic body curvature
□ PSP: Accelerated embryonic body curvature
– Pressure of adjacent structures may interfere with
splenic blood supply leading to development of
ASP/PSP
552

CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ ASP
– Most commonly present with cardiopulmonary
disease (83%), including cyanosis as neonates or in
infancy
– Patients are prone to overwhelming sepsis (especially
postoperatively) due to lack of spleen
– Bowel obstruction (17%) due to malrotation
○ PSP
– 10-15% may not present clinically until adulthood
– Often present with cardiac disease, including heart
murmur, congestive heart failure, occasional cyanosis,
heart block

– Jaundice due to biliary atresia or other biliary
abnormalities
– Abdominal pain related to bowel obstruction or
intestinal ischemia related to malrotation

Demographics
• Age
○ ASP: Newborn or infant presentation
○ PSP: Infant or adult
• Gender
○ ASP: M > F (2:1)
○ PSP: F > M
• Epidemiology
○ ASP: 1 in 40,000 live births
○ Heterotaxia syndromes: 1 in 10,000

Natural History & Prognosis
• ASP: Very poor prognosis
○ Mortality rate: Prognosis depends on extent of cardiac
abnormalities, but only 20% survive to age of 16
• Polysplenia: Fair prognosis, better than asplenia
○ Mortality rate: 50-60% mortality in 1st year, 25% of
patients live up to 5 years, and 10% survive to mid
adolescence

Treatment
• ASP: Prophylactic antibiotics (not needed in PSP)
• Surgical correction of cardiac disease or malrotation in
either ASP or PSP

DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
• Left liver lobe can simulate spleen on US leading to missed
diagnosis of ASP
• Differentiate PSP from accessory spleens and splenosis

SELECTED REFERENCES
1.

Tawfik AM et al: Polysplenia syndrome: a review of the relationship with
viscero-atrial situs and the spectrum of extra-cardiac anomalies. Surg Radiol
Anat. 35(8):647-53, 2013


Asplenia and Polysplenia
Spleen

(Left) Axial CECT in a patient
with PSP syndrome
demonstrates multiple spleens
st located in the right upper
quadrant and situs inversus.
Note the reversed positions of
the liver and stomach. (Right)
Axial CECT in the same patient
demonstrates an abnormal
right-sided stomach st. Note
that the IVC ﬇ is normally
located on the right. The
majority of the small bowel is

on one side of the abdomen, in
keeping with malrotation.

(Left) Axial CECT in a patient
with PSP syndrome shows
dextrocardia and a left-sided
IVC st. (Right) Axial CECT in
the same patient shows
complete abdominal situs
inversus with an otherwise
normal-appearing stomach ſt
and liver on the right-hand
side. Note the left-sided IVC
﬉.

(Left) Axial CECT in the same
patient shows multiple
splenules ſt in the right upper
quadrant along with
abdominal situs inversus.
(Right) Axial CECT in the same
patient shows multiple spleens
ſt, situs inversus, and cystic
disease of the kidneys ﬇. This
patient was 35 years old
(patients with PSP are much
more likely to reach adulthood
than ASP).

553

Spleen

Splenic Infection and Abscess
KEY FACTS

IMAGING
• Pyogenic abscess on CECT
○ Low-attenuation complex fluid collection ± air-fluid levels
○ Internal gas bubbles, which although uncommon, are
very specific for splenic abscess
○ Multiloculated appearance seen with liver abscesses
possible, but less common with splenic abscess
○ May extend to subcapsular location and may rarely cause
splenic rupture with generalized peritonitis
• Fungal microabscesses on CECT
○ Multiple small hypodense lesions measuring a few mm
○ Multiple punctate splenic calcifications after treatment
• Echinococcal (hydatid) cyst on CECT
○ Complex cyst with multiple low density "daughter" cysts
and thick, enhancing wall ("cyst within a cyst")
○ Serpiginous, linear densities within cyst due to collapsed
parasitic membranes (water lily sign)

(Left) Axial CECT shows a
multiloculated mass st within
the spleen that proved to be a
pyogenic abscess. Such large
abscesses are unusual in the

spleen, especially in the
absence of prior splenic
infarction. (Right) Axial CECT
in a patient with a recent
history of traumatic injury to
the spleen and a new fever ſt
demonstrates a rim-enhancing
fluid collection with an airfluid level st, consistent with
a splenic abscess. The patient
was treated with
percutaneous drainage and
antibiotics.

(Left) Axial CECT in a patient
with HIV/AIDS who was
admitted with fever and
weight loss demonstrates
microabscesses st throughout
the spleen. The patient
deteriorated rapidly, and
multiple tuberculous
abscesses were identified at
autopsy. (Right) Axial CECT
shows a splenic hydatid cyst
ſt with additional similar
lesions in the liver and
peritoneal cavity st, many of
which have calcified walls.
This patient had a prior
rupture of a hepatic hydatid

cyst with diffuse spread
throughout the abdomen.

554

○ May demonstrate thick peripheral calcification or
internal wavy, curvilinear calcification in chronic setting

TOP DIFFERENTIAL DIAGNOSES
•
•
•
•

Splenic infarct
Splenic tumor
Splenic trauma
Infiltrating disorders

PATHOLOGY
• Multiple different causes for splenic pyogenic abscesses
○ Generalized septicemia, septic emboli (usually in setting
of endocarditis with mitral &/or aortic valve vegetations),
or secondary infection of traumatic splenic hematoma or
infarct
• Most fungal microabscesses occur in setting of
immunosuppression, HIV/AIDS, or hematologic disorders
• Echinococcal infections occur due to infection with
tapeworm (Echinococcus granulosus)

Splenic Infection and Abscess

Definitions
• Splenic abscess: Collection of liquefied pus within splenic
parenchyma

IMAGING
General Features

MR Findings
• Fluid signal at center of lesion (hyperintense on T2WI and
hypointense on T1WI) with peripheral enhancement on
T1WI C+ images
• Old healed/treated fungal microabscesses may show
blooming artifact on GRE sequences due to calcification

Ultrasonographic Findings

• Best diagnostic clue
○ Rounded low-attenuation complex fluid collection with
mass effect
• Location
○ Variable: May be located anywhere within splenic
parenchyma
• Size
○ Variable: Typically 3-5 cm for pyogenic abscesses; < 1.5
cm for microabscesses (often fungal)
• Morphology
○ Rounded cystic mass with irregular borders

– May have multiple locules similar to cluster sign of
hepatic pyogenic abscess
– Internal septations common
– Exerts mass effect on splenic capsule

• Grayscale ultrasound
○ Pyogenic abscess
– Hypoechoic or anechoic mass with internal septations
and low-level echoes representing pus or debris
□ Rarely, atypical splenic abscess appears echogenic
– May have variable degrees of posterior acoustic
enhancement, depending on cyst contents
– "Dirty" shadowing and ring-down artifact suggest
presence of gas within collection
□ US is much less sensitive for ectopic gas than CT
○ Fungal microabscesses
– "Target" or bull's-eye appearance similar to hepatic
microabscesses
• Color Doppler
○ Pyogenic and fungal abscesses typically show no internal
color flow vascularity

Radiographic Findings

Imaging Recommendations

• Radiography
○ Very rarely gas bubbles within abscess may be visualized
on radiographs
○ Often associated with left lower lobe atelectasis and left

pleural effusion on chest radiograph

• Best imaging tool
○ CECT

CT Findings
• Pyogenic abscess
○ Low-attenuation (20-40 HU) complex fluid collection ±
air-fluid levels
– May have an enhancing peripheral rim, but not as
conspicuous as generally seen with liver abscesses
– May have internal gas bubbles, which although
uncommon, are very specific for splenic abscess
– May have multiloculated appearance seen with liver
abscesses, but less common with splenic abscess
○ May extend to subcapsular location and may rarely cause
splenic rupture with generalized peritonitis
• Fungal microabscesses
○ Often multiple, small, hypodense lesions measuring just
a few mm
○ Can be very difficult to diagnose on NECT
○ May manifest as multiple punctate splenic calcifications
after treatment
• Echinococcal (hydatid) cyst
○ Complex cyst with multiple low density "daughter" cysts
and thick, enhancing wall composed of fibrous tissue
("cyst within a cyst" appearance)
○ Serpiginous, linear hypodense bands within cyst due to
collapsed parasitic membranes (water lily sign)
○ May demonstrate thick peripheral calcification or

internal wavy, curvilinear calcification in chronic setting
○ Similar lesions may be seen in liver or peritoneum

Spleen

TERMINOLOGY

DIFFERENTIAL DIAGNOSIS
Splenic Infarct
• Wedge-shaped area of low attenuation at periphery of
spleen
○ Very rarely rounded in configuration and in central
spleen (potentially mimicking abscess or neoplasm)
• No enhancement on contrast-enhanced images

Splenic Tumor
• May be single or multiple discrete masses
• Most common solid malignancies include lymphoma,
melanoma, and other metastases
○ Melanoma and some cystic/necrotic metastases (ovarian
cancer, sarcomas, germ cell tumors) can appear low
density and cystic, mimicking abscess or fluid collection
○ Lymphoma can present with innumerable tiny
hypodense nodules in spleen mimicking microabscesses
• Most common benign lesions are lymphangioma and
hemangioma
○ Variable appearance; both lesions can appear low density
and mimic abscess or fluid collection
○ Hemangioma may appear hypervascular on arterial
phase CECT and lymphangioma may show internal

loculations and septations

Splenic Trauma
• History of recent blunt injury
• Linear low density, nonenhancing laceration almost always
associated with perisplenic hematoma and
hemoperitoneum
• ± active arterial extravasation

555


Spleen

Splenic Infection and Abscess
Infiltrating Disorders
• Sarcoid (and less commonly, Gaucher disease) can
commonly present with multiple low-attenuation lesions
• Indistinguishable from microabscesses without history
• Sarcoid may be associated with similar lesions in liver,
hepatosplenomegaly, and thoracic/upper abdominal
lymphadenopathy

PATHOLOGY
General Features
• Etiology
○ Multiple different causes for splenic pyogenic abscesses
– Generalized septicemia (most splenic abscesses arise
due to hematogenous spread of infection)
– Septic emboli (usually in setting of endocarditis with

mitral/aortic valve vegetations)
– Secondary infection of traumatic splenic hematoma or
infarct
– Other predisposing risk factors: Recent surgery, other
abdominal infections, intravenous drug abuse,
immunodeficiency, malignancy or hematologic
disorders, trauma, diabetes, and pancreatitis
○ Most fungal microabscesses occur in setting of
immunosuppression, HIV/AIDS, or hematologic disorders
○ Echinococcal infections occur due to infection with
tapeworm (Echinococcus granulosus)
– Most commonly occur in areas with sheep
(transmission often via dogs who eat viscera of
slaughtered animals)
– Most common in South America, Middle East, Eastern
Mediterranean, and parts of Africa
• Genetics
○ Hemoglobinopathies (sickle cell) predispose to pyogenic
abscess

Staging, Grading, & Classification
• Pyogenic
○ Unilocular (65%); multilocular or multiple (20%)
○ Gram-negative organisms in 55%: Klebsiella pneumoniae
most common pathogen
• Fungal
○ Typically microabscesses measuring < 1.5 cm (25%)
○ Most often Candida (most common), Aspergillus, and
Cryptococcus
○ Tuberculosis (TB) and Mycobacterium avium-intracellulare

(MAI) in AIDS patients
• Parasitic
○ Echinococcus granulosus

CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Pyogenic abscess
– Fever (92%), chills, LUQ pain (77%), splenomegaly
– May mimic symptoms of pneumonia, ulcer disease, or
pancreatitis
– Lab data: Leukocytosis (66%), positive blood cultures
○ Echinococcal cyst
– Many patients are asymptomatic and may remain
without symptoms for years
556

– Symptoms depend on site of infection and size of cyst
– Lab data: Eosinophilia in only small minority of
patients (< 15%)

Demographics
• Age
○ Usually adult patients with predisposing factors
(although any age group can be affected)
• Gender
○ M=F
• Ethnicity
○ No known predilection
• Epidemiology

○ Rare: 0.2% of reported autopsies
○ 25% of patients with splenic abscesses are
immunocompromised patients

Natural History & Prognosis
• Excellent prognosis for pyogenic abscesses in
immunocompetent patient
• Guarded prognosis in immunocompromised patients with
fungal microabscesses
• Echinococcal disease can recur many years after treatment
and should be monitored periodically for recurrence

Treatment
• Splenic pyogenic abscess
○ Traditional treatment is splenectomy with broadspectrum antibiotics
– Still standard treatment in setting of multiple
pyogenic abscesses or abscess rupture
– Mortality postsplenectomy: 6%
○ Spleen-conserving treatment increasingly being utilized
– Antibiotics alone may be curative in 75% of small
pyogenic abscesses (< 4 cm)
– Percutaneous drainage may be utilized for unilocular
unruptured abscesses with high reported success
rates
• Fungal microabscesses
○ Treatment with antifungal medications
• Echinococcal cyst
○ Treatment options include surgical resection (especially
in setting of ruptured cysts or other complications),
percutaneous drainage (± introduction of scolicidal

agent), drug therapy (e.g., albendazole), or observation

DIAGNOSTIC CHECKLIST
Consider
• Differentiate splenic abscesses from mimics, including
lymphoma, low-density metastases, or splenic infarcts

Image Interpretation Pearls
• Splenic abscesses appear as solitary or multiple lowattenuation cystic lesions in febrile patient

SELECTED REFERENCES
1.

Tonolini M et al: Nontraumatic splenic emergencies: cross-sectional imaging
findings and triage. Emerg Radiol. 20(4):323-32, 2013


Splenic Infection and Abscess
Spleen

(Left) Color Doppler image
shows a well-defined solitary
splenic abscess with a
hypoechoic necrotic center ſt
and a thick irregular wall st.
The adjacent splenic
parenchyma ﬇ appears
normal. Note the typical
avascular nature of the
abscess. (Right) Axial T1 C+

MR in a patient with LUQ pain
and a fever illustrates the
characteristic multiseptate
appearance of a splenic
abscess ſt. Blood cultures
identified Staphylococcus and
the patient recovered with
antibiotics.

(Left) Axial CECT in a 29-yearold intravenous drug abuser
with a 3-day history of fever
and LUQ pain shows a focal
hypodense lesion ſt in the
periphery of the spleen's
midportion; findings that are
consistent with an abscess.
(Right) Axial CECT in the same
patient reveals lateral
perisplenic inflammatory
changes ſt, suggesting a
possible abscess rupture. An
echocardiogram showed
multiple vegetations in both
the aortic and mitral valves,
suggesting that this abscess is
due to underlying
endocarditis.

(Left) Axial CECT in a 29-yearold known intravenous drug
abuser who presented with

multiple skin abscesses as well
as abdominal pain and fever
demonstrates a lowattenuation splenic abscess
ſt. (Right) Axial CECT in the
same patient demonstrates
multiple hepatic abscesses ſt
as well. The patient
underwent an
echocardiogram, which
additionally revealed aortic
valve vegetations from
endocarditis (not shown).

557


Spleen

Splenomegaly and Hypersplenism
KEY FACTS

TERMINOLOGY
• Splenomegaly: Splenic enlargement caused by a number of
different underlying disorders

IMAGING
• Normal spleen is ≤ 13 cm in length
• Splenic index (product of length, breadth, and width of
spleen): Normally 120-480 cm³
• Splenic weight (splenic index x 0.55): Normally between

100-250 g
• Splenomegaly: AP diameter > 2/3 distance of AP diameter
of abdominal cavity

PATHOLOGY
• Splenomegaly attributable to 5 different general etiologies
○ Congestive
– Right heart failure, portal hypertension, sickle cell
disease (in acute setting), and splenic vein thrombosis
○ Hematologic

(Left) Frontal radiograph
demonstrates "fullness" in the
left upper quadrant. The
inferior edge ﬈ of an
enlarged spleen is evident.
(Right) Coronal T2 MR
demonstrates a markedly
enlarged spleen in a patient
with myelodysplastic
syndrome. The most common
causes of massive
splenomegaly are
cirrhosis/portal hypertension,
lymphoma, chronic
myelogenous leukemia,
extramedullary hematopoiesis,
myelofibrosis, and Gaucher
disease.

(Left) Axial CECT shows a
small, cirrhotic liver with
widened fissures and signs of
portal hypertension, including
splenomegaly and varices st.
In most patients with
splenomegaly, there are clues
as to the underlying cause on
the imaging study, as in this
case. (Right) Coronal CECT in
an asymptomatic patient
demonstrates a mildly
enlarged spleen with multiple
ill-defined hypodense nodules
in a patient with known
sarcoidosis. Lymphoma and
metastatic disease could have
a very similar appearance.

558

– Polycythemia vera, myelofibrosis, and
hemoglobinopathies
○ Inflammatory/infectious
– Mononucleosis and HIV/AIDS most common
infections to result in splenomegaly
– Sarcoid may result in mild splenomegaly with multiple
small hypodensities in liver and spleen
○ Space-occupying lesions
– Space-occupying masses in spleen do not commonly

cause splenomegaly and are more likely to replace
normal splenic tissue
○ Storage and infiltrative disorders
– Primary or secondary hemochromatosis, amyloidosis,
and glycogen storage diseases

CLINICAL ISSUES
• Complications include splenic rupture and hypersplenism
○ Hypersplenism: Hyperfunctioning spleen removes
normal RBC, WBC, and platelets from circulation


Splenomegaly and Hypersplenism

Abbreviations
• Splenomegaly (SMG)
• Hypersplenism (HS)

Definitions
• SMG: Splenic enlargement caused by a number of different
underlying congestive, hematologic,
inflammatory/infectious, neoplastic, or infiltrative disorders
• Hypersplenism: Syndrome consisting of splenomegaly and
pancytopenia in which bone marrow is either normal or
hyperreactive

IMAGING
General Features
• Best diagnostic clue
○ ↑ volume of spleen with convex medial border

• Size
○ No consensus on absolute size thresholds for SMG:
Different sources suggest different measurements
○ Normal spleen is ≤ 13 cm in length
– Width and breadth are usually ≤ 6 and 8 cm,
respectively
○ Splenic index: Normally 120-480 cm³ (product of length,
breadth, and width of spleen)
○ Splenic weight: Splenic index x 0.55
– Normal weight: 100-250 g
○ SMG: Anteroposterior (AP) diameter > 2/3 distance of AP
diameter of abdominal cavity
• Morphology
○ SMG is often associated with abnormal contour of
spleen, including rounding of poles and convexity of
medial border

Radiographic Findings
• Radiography
○ Normal-sized spleen usually not visualized
○ SMG: Splenic tip below 12th rib
○ Marked SMG may displace stomach medially
○ Displacement of splenic flexure of colon (splenic flexure
usually anteromedial to spleen)

CT Findings
• SMG is usually due to 1 of 5 general etiologies
• Congestive
○ Right heart failure: Cardiomegaly with distension of
hepatic veins/IVC and passive hepatic congestion

○ Portal hypertension: Splenomegaly with varices, nodular
shrunken liver, ascites, and other signs of portal
hypertension
○ Splenic or portal vein occlusion or thrombosis (often due
to pancreatitis or pancreatic tumors)
○ Sickle cell disease
– Acute phase: Diffusely decreased splenic density with
splenomegaly
– Chronic phase: Development of small autoinfarcted,
calcified spleen
• Hematologic
○ Polycythemia vera
○ Leukemia

○ Myelofibrosis: SMG due to extramedullary
hematopoiesis
– May be associated with other signs of extramedullary
hematopoiesis (such as paraspinal soft tissue masses)
○ Hemoglobinopathies: May cause splenomegaly
(thalassemia) or small, infarcted spleen (sickle cell [SC])
○ Acute splenic infarction: Global or wedge-shaped
hypoenhancement of splenic parenchyma
• Inflammatory/infectious
○ Mononucleosis
○ Hepatitis: Splenomegaly due to viremia or cirrhosis with
portal hypertension
○ AIDS: SMG may reflect chronic viremia, opportunistic
infection, or lymphoma
○ IV drug abuse: SMG due to chronic low-level sepsis
○ Tuberculosis, histoplasmosis: Multifocal low-density

granulomas acutely that heal as calcified foci
○ Sarcoidosis: Often associated with innumerable small
hypodense splenic granulomas, ± upper abdominal
lymphadenopathy, ± hepatomegaly with similar
hypodense hepatic granulomas
○ Collagen vascular or autoimmune diseases
– Rheumatoid arthritis, scleroderma, etc.
– Felty syndrome: Rheumatoid arthritis, splenomegaly,
and granulocytopenia
○ Malaria: One of the most common causes of SMG
worldwide
• Space-occupying lesions
○ Space-occupying masses do not commonly cause SMG
and are more likely to replace normal splenic tissue
○ Cysts: Common, but usually do not cause SMG
○ Lymphoma and metastases: Relatively common cause of
splenomegaly, especially lymphoma (which may or may
not be associated with discrete hypodense lesions in
spleen)
○ Primary splenic tumors: Do not typically cause SMG
• Storage and infiltrative disorders
○ Secondary hemochromatosis
– Increased density of liver and spleen on NECT (iron
deposition in RES cells)
○ Primary hemochromatosis
– Density of spleen is normal (unlike that of liver)
○ Amyloidosis
– NECT and CECT: Generalized or focal ↓ density
○ Glycogen storage diseases (e.g., Gaucher disease)

Spleen

TERMINOLOGY

MR Findings
• Portal hypertension
○ Gamna-Gandy bodies or siderotic nodules appear as
multiple tiny (3-8 mm) foci of ↓ T1WI and T2WI signal
– Represent hemosiderin deposits related to prior
microhemorrhage
• Hemochromatosis
○ Involved organs (including spleen) are typically markedly
low signal on both T1 and T2WI with signal loss on inphase gradient echo images
○ Primary: Normal signal and size of spleen, with liver and
pancreas most typically involved
○ Secondary: Liver, spleen, bone marrow, and lymph nodes
most often involved
• Sickle cell disease
559


Spleen

Splenomegaly and Hypersplenism
○ Spleen appears low signal on all pulse sequences due to
iron deposition
• Gaucher disease: May present with focal lesions, which
demonstrate either T2WI hypointensity or hyperintensity
• Infarction
○ Peripheral, wedge-shaped areas of abnormal signal that

vary in signal intensity depending on age of infarct and
presence/absence of hemorrhagic transformation
– Acute hemorrhagic infarcts may show high T1WI
signal
– Chronic infarcts tend to be low signal on T1WI and
high signal on T2WI
• Extramedullary hematopoiesis
○ May present with focal T1WI and T2WI hyperintense,
homogeneously enhancing nodules within enlarged
spleen

Ultrasonographic Findings
• Grayscale ultrasound
○ SMG with normal echogenicity
– Infection, congestion (portal hypertension), early
sickle cell disease
– Hereditary spherocytosis, hemolysis, Felty syndrome
– Wilson disease, polycythemia, myelofibrosis, leukemia
○ SMG with hyperechoic splenic parenchyma
– Leukemia, post chemotherapy and radiation therapy
– Malaria, TB, sarcoidosis, polycythemia
– Hereditary spherocytosis, portal vein thrombosis,
hematoma, metastases
○ SMG with hypoechoic splenic parenchyma
– Lymphoma, multiple myeloma, chronic lymphocytic
leukemia
– Congestion from portal hypertension, noncaseating
granulomatous infection
○ Sickle cell disease: Immediately after sequestration,
peripheral hypoechoic areas may be visualized

○ Gaucher disease: Multiple, well-defined, discrete
hypoechoic lesions representing fibrosis or infarction

Imaging Recommendations
• Best imaging tool
○ CECT with multiplanar reformations

DIFFERENTIAL DIAGNOSIS
Other Left Upper Quadrant Masses
• e.g., gastric, renal, adrenal tumors

Splenic Trauma
• Intrasplenic or subcapsular hematoma may enlarge spleen
• Diagnosis usually evident based on imaging and history of
trauma

Splenic Infection and Abscess
• Pyogenic (bacterial) abscess
○ Low-density cystic mass with thick, irregular enhancing
wall ± internal gas and reactive left pleural effusion
• Fungal (e.g., Candida, Aspergillus, Cryptococcus)
○ Low-density lesions that may be solitary or multiple and
of variable size and may show minimal peripheral
enhancement
• AIDS: Pneumocystis, mycobacterial (e.g., Mycobacterium
avium-intracellulare [MAI]) infection
560

○ Focal low-attenuation splenic lesions ± calcification

PATHOLOGY
General Features
• Etiology
○ Congestive SMG
– CHF, portal hypertension, cirrhosis, cystic fibrosis,
splenic vein thrombosis, SC sequestration
○ Neoplasm: Leukemia, lymphoma, metastases, primary
neoplasm, Kaposi sarcoma
○ Storage disease: Gaucher, Niemann-Pick, gargoylism,
amyloidosis, hemochromatosis, histiocytosis
○ Infection: Hepatitis, malaria, mononucleosis, TB, typhoid,
kala-azar, schistosomiasis, brucellosis
○ Hemolytic anemia: Hemoglobinopathy, hereditary
spherocytosis, primary neutropenia, thrombocytopenic
purpura
○ Extramedullary hematopoiesis: Osteopetrosis,
myelofibrosis
○ Collagen disease: SLE, RA, Felty syndrome
○ Most common causes of massive SMG: Lymphoma,
chronic myelogenous leukemia, extramedullary
hematopoiesis, myelofibrosis, and Gaucher disease

CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Many patients asymptomatic, but can result in
abdominal pain or palpable mass in left upper quadrant
○ Signs and symptoms often related to underlying cause

Natural History & Prognosis

• Complications
○ Splenic rupture, shock, and death
• Hypersplenism: Usually develops as result of SMG
○ Hyperfunctioning spleen removes normal RBC, WBC,
and platelets from circulation
○ Up to 90% of all platelets may be removed from
circulation by spleen in cases of severe SMG

Treatment
• Treatment varies based on underlying condition
• Splenectomy in symptomatic and complicated cases

DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
• Look for imaging findings that may explain a patient's
splenomegaly, such as the presence of cirrhosis/portal
hypertension

SELECTED REFERENCES
1.

Manenti A et al: Splenomegaly Secondary to Myeloproliferative Neoplasms
and Portal Hypertension. Clin Lymphoma Myeloma Leuk. ePub, 2014


Splenomegaly and Hypersplenism
Spleen

(Left) Coronal CECT
demonstrates a mildly

enlarged spleen with multiple
hypodense nodules. The
patient was later found to
have thoracic
lymphadenopathy, and biopsy
showed the spleen to be a
manifestation of sarcoidosis.
(Right) Axial T2 MR
demonstrates marked low
signal in the liver, spleen, and
bone marrow in a patient with
hemosiderosis due to multiple
blood transfusions.

(Left) Axial CECT shows a
markedly enlarged spleen with
multiple subtle low-density
foci ſt scattered throughout
the splenic parenchyma. This
was found to be lymphoma,
and lymphadenopathy was
present elsewhere. (Right)
Axial CECT in a patient with
non-Hodgkin lymphoma shows
splenomegaly and extensive
lymphadenopathy ﬈. While
splenomegaly and
lymphadenopathy are
characteristic findings in
patients with NHL, benign

processes, such as sarcoidosis
and mononucleosis, may result
in similar findings.

(Left) Axial arterial phase
CECT in a patient with
cirrhosis & portal hypertension
shows a swirled moiré pattern
of splenic enhancement that
disappeared on the portal
venous phase. This normal
variant is often more
prominent in patients with
cirrhosis and portal
hypertension. (Right) US
shows splenomegaly with
multiple hypoechoic foci ſt in
a patient with granulomatous
MAI infection. On US,
granulomatous abscesses
appear as well-defined,
hypoechoic lesions, usually
with associated splenomegaly.

561


Spleen

Splenic Infarction

KEY FACTS

TERMINOLOGY
• Global or segmental parenchymal splenic ischemia and
necrosis caused by vascular occlusion

IMAGING
• Acute findings on CECT
○ Diagnosis best made on portal venous phase images due
to heterogeneous arterial phase enhancement
○ Global infarction: Complete nonenhancement of spleen
– ± cortical rim sign: Preserved enhancement of
peripheral rim of spleen in massive infarction
○ Segmental infarction: Wedge-shaped or rounded lowattenuation area usually at periphery of spleen
– Can be multiple, especially when caused by emboli
• Chronic findings on CECT
○ Most often results in scarring and volume loss
○ Multiple repetitive infarcts in sickle cell disease can lead
to small, calcified spleen (autoinfarcted spleen)
○ Infarct can develop into splenic cyst

(Left) Axial CECT in a sickle
cell patient demonstrates an
enlarged spleen with multiple
wedge-shaped acute splenic
infarcts st. While sickle cell
patients can develop a small,
calcified autoinfarcted spleen,
the spleen may be enlarged in
the early stages of the disease.

(Right) Axial CECT
demonstrates a large, global
infarct of the spleen with only
a tiny amount of enhancing
splenic tissue ﬇. Notice the
peripheral enhancement (rim
sign) st at the margins of the
infarct as a result of preserved
flow through capsular vessels.

(Left) Axial CECT in a 67-yearold man with a 10-year history
of atrial fibrillation, now
presenting with acute LUQ
pain, demonstrates a
peripheral, low-attenuation
splenic infarct with straight
margins ſt. (Right) Axial
CECT in the same patient
identifies a left ventricular
thrombus ﬈ as the source of
the arterial embolus to the
spleen. Embolic disease is
likely the most common cause
of splenic infarcts in older
patients.

562

• Complications (< 20% of patients)
○ Perisplenic fluid/hematoma suggests splenic rupture

○ Development of rim-enhancing fluid collection: Splenic
abscess

TOP DIFFERENTIAL DIAGNOSES
•
•
•
•

Splenic laceration
Splenic cyst or abscess
Heterogeneous arterial phase enhancement of spleen
Splenic tumors

CLINICAL ISSUES
• Many different causes, but 2 most common are
○ Hematologic disease or hematologic malignancies (sickle
cell, myelofibrosis, leukemia, etc.)
○ Embolic conditions (septic emboli, cardiac emboli from
atrial fibrillation, etc.)
• Most cases require no treatment, but rarely surgery or
intervention for pain or complications


Splenic Infarction

Definitions
• Global or segmental parenchymal splenic ischemia and
necrosis caused by vascular occlusion

IMAGING

□ Sites of old infarcts may show calcification
□ Remaining spleen may undergo compensatory
hypertrophy
– Multiple repetitive infarcts in sickle cell disease can
lead to a small, calcified spleen (autoinfarcted spleen)
– Infarct can develop into splenic cyst (secondary or
acquired cyst)

General Features

MR Findings

• Best diagnostic clue
○ Peripheral, wedge-shaped, nonenhancing areas within
splenic parenchyma on CECT in patients with LUQ pain
• Location
○ Entire spleen may be infarcted or more commonly
segmental areas
• Morphology
○ Most commonly wedge-shaped areas of
nonenhancement when infarct is segmental
– Straight margins indicate vascular etiology (rather
than a mass or fluid collection)
– May very rarely be rounded (atypical appearance)

• T1WI
○ Low signal within area of infarct (can show high T1WI
signal due to hemorrhagic infarct)

• T2WI
○ Heterogeneous high signal within area of infarct
• T1WI C+
○ Wedge-shaped area of hypoenhancement

Radiographic Findings
• Radiography
○ May be associated with lower left lobe atelectasis and
pleural effusion on chest x-ray

CT Findings
• NECT
○ Infarcts may be difficult (or impossible) to visualize
without intravenous contrast
○ Areas of hemorrhagic transformation within infarcts
appear hyperdense on NECT
• CECT
○ Acute findings
– Diagnosis best made on portal venous phase images:
Heterogeneous enhancement during arterial phase
(due to differential enhancement of red and white
pulp) makes identification of subtle infarcts difficult
– Global: Complete nonenhancement of spleen
□ ± cortical rim sign: Preserved enhancement of
peripheral rim of spleen in massive infarction due
to preserved flow from capsular vessels
□ Mottled higher density areas within infarcted
spleen may represent either tiny islands of residual
enhancing splenic tissue or hemorrhage
– Segmental: Wedge-shaped or rounded lowattenuation area usually at periphery of spleen

□ Can be multiple, especially when caused by emboli
□ In some instances, accessory spleens (splenules)
may be infarcted
□ Spleen may or may not be enlarged in acute phase
– Complications (< 20% of patients)
□ Presence of fluid or hematoma surrounding spleen
in setting of infarct suggests splenic rupture (most
often in setting of large or global infarct)
□ Development of discrete rim-enhancing fluid
collection ± internal gas should raise concern for
splenic abscess
○ Chronic findings
– Infarcts should evolve over time, leaving areas of
scarring and volume loss in spleen

Spleen

TERMINOLOGY

Ultrasonographic Findings
• Grayscale ultrasound
○ Wedge-shaped hypoechoic area(s) within periphery of
spleen
– May rarely be rounded or irregularly shaped at center
of spleen (atypical)
○ Bright band sign: Highly echogenic linear bands in area of
infarct may be specific sign of infarction
• Color Doppler
○ Diminished or absent flow in areas of infarction

Angiographic Findings
• Conventional angiography: Main splenic artery occlusion or
segmental emboli

Imaging Recommendations
• Best imaging tool
○ Portal venous phase CECT

DIFFERENTIAL DIAGNOSIS
Splenic Laceration
• Hypodense, wedge-shaped defect in spleen in patient with
recent history of trauma
• Almost always high-attenuation hematoma adjacent to
laceration ± large hemoperitoneum
• May have high-attenuation active arterial extravasation

Splenic Cyst
• Nonneoplastic cysts divided into primary "true" epithelial
cysts and secondary "false" cysts (no epithelial lining)
○ Primary cysts most often epidermoid cysts (10-25% of all
splenic cysts), but can be parasitic (echinococcal)
○ Secondary cysts result from prior infection, infarction,
trauma, or hematoma
• Usually well-defined, rounded fluid attenuation cyst with
variable internal complexity and peripheral calcification
• Can result from prior infarct, but much better defined,
rounded, and water density

Splenic Abscess
• Complex intraparenchymal or perisplenic loculated fluid

collection with peripheral enhancement, internal
complexity/debris, and possible internal gas
• Unlike infarct, splenic abscess is a discrete, rounded fluid
collection with adjacent fat stranding/inflammation
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Spleen

Splenic Infarction
○ May develop from evolution of prior infarct
• May appear as multiple small lesions (microabscesses) due
to fungal infections in immunocompromised patients

Normal Heterogeneous Enhancement of Spleen in
Arterial Phase
• Striated appearance of spleen in arterial phase (due to
differential enhancement of red and white pulp) should not
be confused with splenic infarcts

Splenic Tumors
• Primary or secondary neoplasms of spleen (whether benign
or malignant) should appear focal and mass-like, with
rounded borders (not wedge-shaped or linear)
• Lymphoma and some metastases (metastatic melanoma or
mucinous neoplasms) may appear low density and
hypoenhancing, resembling density of infarcts

PATHOLOGY
General Features

• Etiology
○ Large variety of different causes resulting in occlusion of
arterial/venous vasculature supplying spleen
– Hematologic disorders
□ Sickle cell hemoglobinopathies: Risk of splenic
infarct during high-altitude travel or airplane flight
□ Myelofibrosis
□ Hypercoagulable states
□ Leukemia and lymphoma
□ Any cause of hypersplenism/splenomegaly
(including mononucleosis and infections)
– Thromboembolism
□ Atrial fibrillation
□ Aortic atherosclerotic disease with embolization to
splenic artery
□ Aortic valve emboli from subacute bacterial
endocarditis
– Anatomic causes
□ Splenic torsion (including torsion due to wandering
spleen): Laxity or absence of splenic ligaments
results in spleen "wandering" to ectopic locations,
increasing incidence of torsion and infarction
– Miscellaneous
□ Pancreatitis or pseudocysts
□ Portal hypertension
□ Any surgical procedure involving upper abdominal
organs (particularly pancreatic tail, stomach, left
adrenal gland)
□ Collagen vascular disease
□ Tumors (gastric, pancreatic, adrenal) involving

splenic hilum and vessels

CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Many patients can be asymptomatic (1/3 of patients)
– Most common with small splenic infarcts
○ Most common symptoms: LUQ pain, fever, chills,
malaise, nausea, vomiting
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○ May be associated with other infarcts (e.g., kidney and
bowel) in patients with splenic infarcts due to emboli
• Lab data: Anemia (53%), leukocytosis (41%), elevated
platelet count (7%)

Demographics
• Age
○ 2-87 years (mean: 54)
• Gender
○ M=F
• Epidemiology
○ Many different causes, but 2 most common causes are
– Hematologic disease or hematologic malignancies:
Sickle cell, myelofibrosis, leukemia, etc; most common
causes in younger patients
□ Probably caused by congestion and occlusion of
splenic vessels by abnormal cells associated with
hematologic disorder
□ Most common cause of splenic infarcts overall

– Embolic conditions (septic emboli, cardiac emboli
from atrial fibrillation, embolization of ulcerated
atherosclerotic plaque); most common cause in older
patients

Natural History & Prognosis
• Most cases require no treatment and symptoms cease
naturally
• Rarely surgery or intervention for pain or complications
○ Complications: Abscess, rupture, subcapsular hematoma,
hemorrhage, pseudocyst formation

Treatment
• Asymptomatic: Supportive treatment (pain control with
analgesics)
• Symptomatic: Splenectomy for intolerable/increasing pain
or splenic rupture; image-guided drainage for splenic
abscess formation

DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
• Wedge-shaped, peripheral area of nonenhancement on
portal venous phase CECT
• Do not confuse normal striated enhancement pattern on
arterial phase CECT for splenic infarct

SELECTED REFERENCES
1.

2.

3.

Gaetke-Udager K et al: Multimodality imaging of splenic lesions and the role
of non-vascular, image-guided intervention. Abdom Imaging. 39(3):570-87,
2014
Llewellyn ME et al: The sonographic "bright band sign" of splenic infarction. J
Ultrasound Med. 33(6):929-38, 2014
Lawrence YR et al: Splenic infarction: an update on William Osler's
observations. Isr Med Assoc J. 12(6):362-5, 2010


Splenic Infarction
Spleen

(Left) Axial CECT in a young
child with acute abdominal
pain demonstrates a large,
hypoenhancing mass ſt in the
pelvis. (Right) Coronal CECT in
the same patient again shows
the same mass ſt in the pelvis
with fluid in the adjacent right
pelvis st and no spleen noted
in the abdomen. This mass was
found at surgery to represent
torsion and infarction of a
"wandering" spleen. The
spleen in such cases is found in
ectopic locations due to laxity
or absence of the splenic

ligaments.

(Left) A large fluid collection
st envelops small areas of
normal splenic tissue ſt. This
was found at surgery to
represent a massively
infarcted spleen with
contained rupture, resulting in
the fluid collection. (Right)
Patient status post
embolization for
hypersplenism shows severe
splenomegaly with no
enhancement except for a
small portion of the medial
spleen st. Massive acute
infarction is often not desired
in splenic embolotherapy, as
patients can develop
infections of infarcted tissue.

(Left) Sagittal ultrasound in a
48-year-old woman with
myelodysplastic syndrome and
a 1-week history of LUQ pain
shows marked splenomegaly &
a wedge-shaped hypoechoic
area ſt in the lower pole of
the spleen, consistent with

infarction. The patient was
placed on analgesics and
recovered uneventfully.
(Right) Axial NECT in a 55year-old woman presenting
with a history of sickle cell
anemia demonstrates a spleen
that is very small, densely
calcified ſt, and
nonfunctional, sometimes
termed "autosplenectomy."

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Spleen

Splenic Trauma
KEY FACTS

TERMINOLOGY
• Splenic parenchymal injury ± capsule disruption

IMAGING
• High-attenuation hemoperitoneum > 30 HU or perisplenic
clot > 45 HU
○ Perisplenic hematoma: Located adjacent to spleen and
implies disruption or rupture of splenic capsule
○ Intraparenchymal hematoma: Typically round or irregular
in shape
○ Subcapsular hematoma: Constrained by splenic capsule

and crescentic in shape
• Sentinel clot sign: Highest density blood localizes adjacent
to spleen (or any site of injury)
○ Indicates splenic injury even without demonstrable
laceration
• Parenchymal laceration: Irregular linear, branching, or
stellate area of nonenhancing low attenuation

(Left) Axial CECT in an 87year-old woman who fell at a
nursing home demonstrates a
splenic parenchymal
laceration ﬈ and
intraperitoneal blood st, as
well as a lentiform
heterogeneous and higher
attenuation collection
flattening the normal convex
lateral splenic contour,
representing a subcapsular
hematoma ﬊. (Right) Axial
CECT in a 23-year-old man
injured in a motor vehicle
accident shows a shattered
spleen with a sentinel clot ſt
in the perisplenic region and
large hemoperitoneum ﬉.

(Left) Axial CECT in a 19-yearold man who was an
unrestrained passenger in a
motor vehicle accident shows

marked upper abdominal
hemoperitoneum ſt, a
shattered spleen with
intrasplenic high-attenuation
pseudoaneurysms st, and a
focus of active arterial
extravasation lateral to the
spleen within the peritoneal
cavity ﬇. (Right) Axial CECT
in the same patient shows the
active arterial extravasation
ſt extending into the left
paracolic gutter with
surrounding hemoperitoneum
st.

566

• Splenic fracture: Deep laceration extending from outer
capsule through splenic hilum
• Splenic infarction: Unusual (< 2% of cases) in the setting of
trauma, and can be segmental or complete
• Active arterial extravasation: High-attenuation focus
isodense with aorta, surrounded by lower attenuation clot
or hematoma
○ Distinction between active extravasation and
pseudoaneurysm using delayed phase images

CLINICAL ISSUES
• Most commonly injured solid abdominal organ in blunt

trauma and most common abdominal organ injury
requiring surgery
• Prone to develop delayed hemorrhage, but excellent
prognosis with early intervention (surgery/embolization)
• Identification of active arterial extravasation or
pseudoaneurysm best predictor of need for surgery and
failure of nonoperative management


Splenic Trauma

Synonyms
• Splenic laceration or splenic fracture

Definitions
• Splenic parenchymal injury ± capsule disruption

IMAGING
General Features
• Best diagnostic clue
○ Low-attenuation splenic laceration with high-density
active bleeding

○ Active arterial extravasation: High-attenuation focus
isodense with aorta, surrounded by lower attenuation
clot or hematoma
– May be linear (spurting vessel) or rounded
(pseudoaneurysm): Distinction is made using delayed
phase images
□ Active extravasation (unlike pseudoaneurysm)

changes in size and morphology between initial and
delayed phases
□ Although delayed images are not routinely included
in most trauma protocols, addition of delayed
images can be helpful if there is site of suspicion
noted on initially acquired portal venous phase
images

Radiographic Findings

Ultrasonographic Findings

• Radiography
○ Abdominal radiography
– Left upper quadrant soft tissue mass
– Signs of intraperitoneal fluid with widening of
distance between flank strip and descending colon
– Fluid in pelvis with prominent pelvic "dog ears"
○ Chest radiography demonstrates associated injuries
– Lower left lobe atelectasis &/or consolidation
– Left rib fractures, pneumothorax, pleural effusion

• Subtle laceration may be missed, as ultrasound is insensitive
for parenchymal injury
○ Lacerations can be hypoechoic or isoechoic to splenic
parenchyma and can be very difficult to detect with US
• Free intraperitoneal fluid with low-level echoes
representing hemoperitoneum and echogenic perisplenic
clot

CT Findings
• NECT
○ High-attenuation hemoperitoneum > 30 HU or
perisplenic clot > 45 HU
– Perisplenic, intraparenchymal, or subcapsular
hematoma
□ Perisplenic hematoma: Located adjacent to spleen
and implies disruption or rupture of splenic capsule
□ Intraparenchymal hematoma: Typically round,
ovoid, or irregular in shape
□ Subcapsular hematoma: Constrained by splenic
capsule; crescentic in shape and compresses lateral
margin of parenchyma
○ Sentinel clot sign: Highest density blood localizes
adjacent to spleen (or any site of injury)
– Indicates splenic injury even in absence of
demonstrable laceration
○ Layered or lamellated clot if bleeding is intermittent
• CECT
○ Parenchymal laceration: Irregular linear, branching, or
stellate area of nonenhancing low attenuation within
parenchyma
– May extend to splenic capsule resulting in capsular
tear
– Should become less conspicuous on follow-up
imaging
○ Splenic fracture: Deep laceration extending from outer
capsule through splenic hilum
○ Splenic infarction: Unusual (< 2% of cases) in setting of
trauma

– Can be segmental or complete
– Wedge-shaped area of hypoattenuation
– Due to arterial thrombosis after intimal injury
– Risk of delayed rupture or abscess formation

Spleen

TERMINOLOGY

Angiographic Findings
• Avascular parenchymal laceration with amorphous
parenchymal extravasation
• Flattened lateral contour of spleen due to subcapsular
hematoma
• Rounded contrast collections (pseudoaneurysms)

Imaging Recommendations
• Best imaging tool
○ CECT
• Protocol advice
○ Arterial phase images more sensitive for active
extravasation or pseudoaneurysm
○ Portal venous phase images more sensitive for
parenchymal injury (i.e., laceration)
○ Delayed images to differentiate active arterial
extravasation from pseudoaneurysm

DIFFERENTIAL DIAGNOSIS
Splenic Cleft
• Normal anatomic variant that appears as a thin, fissure-like

band of low attenuation
• Most often occurs at upper or lower pole of spleen
• No evidence of adjacent hematoma, free fluid, or stranding

Splenic Abscess
• Rounded, irregular, low-attenuation collection within
splenic parenchyma
• Clinical signs of infection: Fever, increased white blood cell
count, left pleural effusion
• No history of trauma or hemoperitoneum

Splenic Infarct
• Wedge-shaped area of low attenuation usually located at
periphery of spleen
• Associated with splenomegaly, systemic emboli (such as
from endocarditis), and multiple other causes

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