Pediatric emergency medicine trisk 574

Renal Abscesses
Renal abscesses can occur as either a complication of pyelonephritis, where they typically are caused by gramnegative rods, or from hematogenous seeding from systemic bacteremia, in which case S. aureus is the most
common etiology. Risk factors for renal abscesses due to pyelonephritis include anatomic obstruction (e.g.,
nephrolithiasis) or vesicoureteral reflux. These abscesses can occur in either the renal cortex or medulla. Risk
factors for hematogenous spread include endocarditis or intravenous drug use; in some instances, children have
had a preceding minor skin infection, with transient bacteremia seeding the kidneys. These abscesses primarily are
found in the renal cortex. Symptoms include fever, malaise, back or abdominal pain, and weight loss. The absence
of dysuria does not exclude a renal abscess. Costovertebral angle tenderness is found in a majority of adults, but is
less sensitive in children.
Laboratory findings include leukocytosis with a left shift and elevated erythrocyte sedimentation rate (ESR) and
CRP. Patients whose abscesses connect with the collecting system may have urinalyses demonstrating pyuria,
proteinuria, and bacteriuria. For patients whose abscesses are due to hematogenous spread, initial urinalyses can be
normal, but the organism will grow in culture. Renal abscesses should always be suspected in a child with a
presumed S. aureus UTI. Ultrasound often cannot distinguish a purulent collection from a hematoma, whereas a
contrasted CT can help determine the extent of disease. Medical management alone is usually sufficient for renal
abscesses less than 5 cm in diameter, whereas percutaneous drainage in addition to antibiotics is needed for larger
abscesses. Broad-spectrum antibiotics covering both gram-negative organisms (pseudomonal coverage should be
considered for immunocompromised hosts or persons who previously have had pseudomonal UTIs) and S. aureus
should be started pending culture results. Improvement is followed clinically (fever curve) and through laboratory
parameters (normalization of white count and inflammatory markers). Standard precautions are indicated.

SKIN AND SOFT TISSUE INFECTIOUS EMERGENCIES
The major infections of the skin, soft tissues, and bones include impetigo, cutaneous abscesses, cellulitis and
superficial abscesses, fasciitis, septic arthritis, and osteomyelitis. Additionally, mastitis and omphalitis occur in the
neonate. Among the disorders in this group, impetigo and cellulitis are both common complaints in the ED.
Although children with bone and joint infections are seen infrequently, the differential diagnosis of several
common complaints (e.g., fever, limp) often includes these conditions. Thus, the emergency clinician who cares
for children should be familiar with such infections, particularly because a prolonged delay in the institution of
therapy can result in appreciable morbidity.

Impetigo

Impetigo is a superficial pustular infection of the epidermis. In contrast, ecthyma involves the dermis. Bullous
impetigo is characterized by lesions greater than 1 cm in diameter. GAS is the most common cause of impetigo,
while S. aureus is the most common cause of bullous impetigo, but can also cause nonbullous impetigo. Impetigo
is predominantly a disease of the preschool-aged child, and is more common during summer months. Children
typically lack systemic signs and symptoms of infection. Skin findings include honey-crusted or bullous lesions
with minimal surrounding erythema or induration; regional adenopathy is not common. Routine laboratory
evaluation is unnecessary in the well-appearing, previously healthy child. Complications may include cellulitis and
glomerulonephritis if the child is infected with a nephritogenic strain. The risk of renal disease is not decreased by
treatment of local infection. Mupirocin can eradicate most cases of impetigo, especially if the disease is limited in
distribution, and may decrease selection for antibiotic resistance. Systemic therapy may be indicated for bullous
impetigo or if use of topical antibiotics is impractical due to extent of disease. Oral treatment options include
cephalexin, or clindamycin. TMP-SMZ offers coverage for the vast majority of staphylococcal isolates (both
MRSA and MSSA), but does not cover GAS. Knowledge of the rates of MRSA in your area can help optimize
empiric antibiotic therapy. Contact precautions should be used.

Cellulitis
Cellulitis is an infection of the skin and subcutaneous tissues. A related disease is erysipelas, which involves the
more superficial skin layers. Erysipelas lesions are beefy red, raised above the skin surface, and have very welldemarcated borders; the most common cause is GAS. The most common causes of cellulitis by location and
exposure type are listed in e-Table 94.12 . Clinical manifestations include erythema, edema, warmth, and pain;
only 10% to 20% develop fever. Regional adenopathy is common. Blood cultures rarely are positive in wellappearing immunocompetent hosts, except in children with pneumococcal, H. influenzae, or group B streptococcal


disease. However, these children are usually not well appearing. Needle aspirates from the center of the cellulitic
region are positive in between 5% and 40% of cases, with punch biopsies having a higher culture yield. Bedside
ultrasound may allow the clinician to differentiate abscesses from cellulitis. Treatment should be directed at S.
aureus and GAS, with empiric selection guided by the local prevalence of MRSA and past cultures. While most
children with cellulitis can be managed in the outpatient setting, initial parenteral therapy should be considered in
the following cases: immunocompromised; toxic-appearance; rapidly progressive lesions; facial or circumferential
involvement; crepitance or violaceous skin discoloration; or pain out of proportion to examination. The latter two
findings should prompt evaluation for necrotizing fasciitis and immediate surgical consultation. Standard

precautions should be used unless draining lesions exist, in which case contact precautions should be implemented.

Mastitis, Neonatal
Mastitis is an infection of breast tissue; in neonates, it is most commonly seen in the first 3 weeks of life and is
more common in girls and in term infants. The most common etiology is S. aureus, but GBS, E. coli, and
Salmonella can also cause neonatal mastitis. Infants present with unilateral painful erythema and induration of the
breast bud. Fever may be absent even in bacteremic children. Blood cultures usually are negative; cultures of
purulent drainage often are positive. Empiric antibiotic coverage should include nafcillin (for coverage of GAS,
GBS) and gentamicin and vancomycin if the child lives in an area with high MRSA prevalence. Incision and
drainage is advisable in the case of local fluctuance, with careful attention to avoiding injury to the developing
breast bud, which is already at risk of damage from the infectious process and may lead to cosmetic issues of the
breast first noted at adolescence. Standard precautions should be used unless draining lesions exist, in which case
contact precautions should be implemented.

Omphalitis
Omphalitis is an infection of the umbilical stump and surrounding tissues. The most common pathogens are S.
aureus and GAS; GBS (Streptococcus agalactiae ) and gram-negative enterics can also cause omphalitis. The
incidence has decreased in industrialized countries because of triple dye placed on the stump immediately after
delivery; omphalitis usually is seen in the first 14 days of life. It is more common in premature infants and in
infants with complicated deliveries. The first symptoms are purulent, foul-smelling drainage and later erythema
around the stump (ultimately, many children have erythema that completely encircles the stump). Later
manifestations include lethargy, fever or hypothermia, and irritability; late examination findings include erythema
and induration of the anterior abdominal wall. Minimal drainage or noncircumferential erythema is not sufficient
to diagnose omphalitis, as some drainage from the umbilical stump is common in the absence of infection.
Evaluation for bacteremia and other systemic disease is necessary; Gram stain and cultures from umbilical
drainage should be sent. Empiric antibiotic coverage should include nafcillin (for coverage of GAS, GBS) and
gentamicin and vancomycin if the child lives in an area with high MRSA prevalence. Standard precautions should
be used unless draining lesions exist, in which case contact precautions should be implemented.

Septic Arthritis

CLINICAL PEARLS AND PITFALLS
Children with septic arthritis present with joint pain (and refusal to walk, if the affected joint is in the
lower extremities) and decreased range of motion.
Laboratory findings supportive of the diagnosis of septic arthritis include elevated inflammatory
markers.
The definitive diagnosis is made via arthrocentesis and culture. Cell count parameters allow the
clinician to help differentiate between inflammatory and infectious etiologies.
Empiric therapy for septic arthritis outside the neonatal period should target S. aureus, the most
common cause of septic arthritis.
In Lyme-endemic regions, B. burgdorferi can also cause arthritis, though the children with Lyme
arthritis typically have less fulminant courses than with pyogenic arthritis.
Current Evidence


Septic arthritis is a bacterial infection of the joint space. The etiologies vary by age. In the neonatal period and
early infancy, GBS and S. aureus are the predominant pathogens, with gram-negative bacilli and Candida seen
sporadically, especially in hospitalized infants. Beyond this time period, S. aureus overwhelmingly is the most
common pathogen causing septic arthritis. Pneumococcus, GAS, gonococcus, and K. kingae also are associated
with septic arthritis in children. Salmonella can be seen in children with hemoglobinopathies. Brucella septic
arthritis can be associated with consumption of unpasteurized milk products and has a predilection for the
sacroiliac joint. Neisseria gonorrhea can cause a monoarticular arthritis can be seen in sexually active adolescents.
Hib is a rare cause of septic arthritis in the modern era. Lyme arthritis and tuberculosis arthritis are discussed
elsewhere.
Goals of Treatment
The goal of treatment is to rapidly identify children with septic arthritis so that prompt arthrocentesis can be
performed and antibiotics administered. Clinical outcomes include orthopedic sequelae (e.g., chondrolysis,
osteonecrosis) and differentiation of septic arthritis from other orthopedic complaints of childhood.
Clinical Considerations
Clinical recognition: The most common manifestation is limp, as 90% of children with septic arthritis have
monoarticular involvement of a lower extremity joint. In the child who is limping or refusing to ambulate,

occasionally it will be difficult to determine a focal lesion after manipulation of the lower extremity joints and
palpation of the long bones. Clinicians should be sure to evaluate the sole of the foot for foreign bodies and also to
palpate over the sacroiliac joint to assess for tenderness. Pain may be referred to other areas (e.g., hip septic
arthritis presenting as knee pain). The child with a septic hip often lies quite still with the leg abducted and in
external rotation. Fever is present in almost two-thirds of children with septic arthritis, but can be absent in
adolescents with gonococcal infections or in neonates. An erythematous swelling may surround a superficial joint
that is infected. Although a temperature difference exists between the affected and unaffected sites, it can be
difficult to discern in the febrile child. Inflammation within the joint distends the capsule and produces pain with
movement. If a child allows the physician to manipulate an extremity through a full range of motion, septic
arthritis is unlikely.
Triage considerations: Any child with fever and a limp or other joint complaint should be promptly evaluated
for septic arthritis. The most urgent of locations is septic arthritis of the hip, as this can result in compromised
vascular flow to the femoral capitis. Associated tachycardia and/or hypotension can imply sepsis and would
require fluid resuscitation.
Clinical assessment: Septic arthritis is diagnosed via aspiration and culture of joint fluid. Arthrocentesis is not
only diagnostic, it is therapeutic; many children report decreased pain after synovial fluid is aspirated. As such,
early consultation with orthopedic surgery is critical. Most children with pyogenic septic arthritis have synovial
fluid white blood cell count (WBC) of >50,000 cells/mm3 and a neutrophilic predominance. However, cell counts
may be lower with Brucella or tuberculosis arthritis and may exceed 50,000 cells/mm3 with some noninfectious
causes of arthritis, such as juvenile idiopathic arthritis. A Gram stain should be sent, as some organisms may be
seen in the synovial fluid and not grown in culture, even in children without antibiotic pretreatment, as synovial
fluid has some bacteriostatic properties. Approximately 50% of children with septic arthritis will have positive
synovial fluid cultures. Culture yield is enhanced for certain pathogens with appropriate specimen handling. If
Kingella is suspected, synovial fluid should be injected into a blood culture bottle to increase yield. If Brucella is
suspected, the laboratory should be notified so that the cultures can be kept far beyond the usual protocol, as it
often takes weeks for this organism to grow. Acid-fast cultures and M. tuberculosis PCR should be sent in
immunocompromised hosts or children with epidemiologic risk factors for tuberculosis. Fungal, anaerobic, and
acid-fast cultures (the latter for nontuberculous mycobacteria) should be obtained in children with penetrating
trauma, as these infections often are polymicrobial and can be caused by a broad spectrum of pathogens.
Ancillary laboratory evaluation should include a blood culture, complete blood count, ESR, and CRP. The ESR

and CRP are the most consistent abnormal laboratory studies and can be used to monitor response to therapy.
Radiographic studies (e.g., MRI) can be used to evaluate for contiguous osteomyelitis. This is particularly common
in the first year of life, because at this time, the metaphysis is located within the joint capsule. Recognition of
osteomyelitis in association with septic arthritis is an important consideration when determining the duration of
therapy.


Clinical algorithms have been developed for septic arthritis. The best known is the Kocher criteria for septic
arthritis of the hip. The risk factors assessed were nonweight bearing on the affected side, ESR >40 mm/hr, fever,
and WBC >12,000/mm3. When all four criteria are met, there is a 99% chance that the child has septic arthritis.
However, the negative predictive value is not as robust; 40% of cases with only 2/4 criteria have a septic joint.
Management: Prompt surgical intervention is typically advocated for septic arthritis of the hip. All children with
suspected septic arthritis should be admitted to the hospital for parenteral antibiotics. Antistaphylococcal coverage
should be initiated in children of any age with suspected septic arthritis. The selection of vancomycin over
clindamycin depends upon local antibiotic susceptibility patterns, illness severity, and any prior culture results
available for the child. Coverage should be expanded beyond staphylococcal coverage if the Gram stain
demonstrates organisms other than gram-positive cocci in clusters, if gonococcal arthritis is suspected based upon
history or cultures from nonjoint sites (e.g., oropharynx, rectum), or in immunocompromised children or children
whose arthritis is due to penetrating trauma to the joint. In neonates and young infants, ampicillin and a thirdgeneration cephalosporin should be added to augment coverage for GBS and gram-negative rods. Standard
precautions should be used unless draining lesions exist, in which case contact precautions should be implemented.

Lyme Disease Arthritis
A common cause of septic arthritis in Lyme-endemic regions (northeastern, mid-Atlantic, and Great Lakes states in
the United States) is B. burgdorferi. Lyme arthritis is a monoarticular or pauciarticular (affecting 2 to 4 joints)
arthritis that most often affects the large joints, especially the knees, which are involved in over 90% of cases.
After the knee, the shoulder, ankle, and elbow are the most commonly affected joints. It affects approximately 7%
of children with Lyme disease. The symptoms mimic those of septic arthritis caused by pyogenic organisms (acute
bacterial septic arthritis). There are some features that can enable the provider to differentiate the two entities (
e-Table 94.13 ). One clinical prediction rule derived and validated in a Lyme-endemic region showed that children
were at low risk for septic arthritis if the ANC was <10,000/mm3 and the ESR was <40 mm/hr. Serologic tests are

insensitive in the first month after Lyme infection, but are always positive when arthritis exists. Tiered screening,
beginning with an enzyme immunoassay (EIA) or immunofluorescent antibody (IFA) assay, with confirmation of
positive results by a Western blot, is recommended. Two-step screening is needed because false positives on EIA
or IFA can occur due to other spirochete infections, varicella, EBV, and some collagen vascular disorders. Lyme
serologies should not be sent in children who have not lived in or traveled to Lyme-endemic regions, as any
positive results in these children are far more likely to represent false positives. The treatment of initial and
recurrent arthritis due to Lyme disease is summarized in e-Table 94.14 . Macrolides are less effective than other
antibiotics, and as such are recommended only for patients who cannot tolerate cephalosporins, penicillins, or
tetracyclines. Standard precautions are used for children with suspected Lyme disease.

Osteomyelitis
CLINICAL PEARLS AND PITFALLS
Children with osteomyelitis usually present with fever and focal bone pain. Range of motion may be
limited by pain, and findings can thus mimic septic arthritis.
The most common cause of osteomyelitis is S. aureus.
Blood cultures are positive in approximately 50% of children, as such, bone biopsy should be
attempted. Under optimal circumstances, the biopsy would occur prior to the child receiving
antibiotics, if the child is nontoxic and immunocompetent.
Current Evidence
Osteomyelitis is a bacterial infection of the bone. In 90% of cases, only one bone (most commonly in the lower
extremity) is involved. The upper extremity is involved in approximately 25% of cases. The most common cause,
across all age groups, is S. aureus. There is substantial overlap between the organisms causing septic arthritis and
those causing osteomyelitis. P. aeruginosa may infect the bones of the foot after a puncture wound. In children
with sickle cell disease and other hemoglobinopathies, Salmonella species account for almost half the cases of
osteomyelitis. Atypical pathogens may be recovered from immunocompromised children.
Goals of Treatment