Chapter 045. Azotemia and Urinary Abnormalities (Part 1) pot

Chapter 045. Azotemia and
Urinary Abnormalities
(Part 1)

Harrison's Internal Medicine > Chapter 45. Azotemia and Urinary
Abnormalities
Azotemia and Urinary Abnormalities: Introduction
Normal kidney functions occur through numerous cellular processes to
maintain body homeostasis. Disturbances in any of these functions can lead to a
constellation of abnormalities that may be detrimental to survival. The clinical
manifestations of these disorders will depend upon the pathophysiology of the
renal injury and will often be initially identified as a complex of symptoms,
abnormal physical findings, and laboratory changes that together make possible
the identification of specific syndromes. These renal syndromes (Table 45-1) may
arise as the consequence of a systemic illness or can occur as a primary renal
disease. Nephrologic syndromes usually consist of several elements that reflect the
underlying pathologic processes. The duration and severity of the disease will
affect these findings and typically include one or more of the following: (1)
disturbances in urine volume (oliguria, anuria, polyuria); (2) abnormalities of
urine sediment [red blood cells (RBC); white blood cells, casts, and crystals]; (3)
abnormal excretion of serum proteins (proteinuria); (4) reduction in glomerular
filtration rate (GFR) (azotemia); (5) presence of hypertension and/or expanded
total body fluid volume (edema); (6) electrolyte abnormalities; or (7) in some
syndromes, fever/pain. The combination of these findings should permit
identification of one of the major nephrologic syndromes (Table 45-1) and will
allow differential diagnoses to be narrowed and the appropriate diagnostic
evaluation and therapeutic course to be determined. Each of these syndromes and
their associated diseases are discussed in more detail in subsequent chapters. This
chapter will focus on several aspects of renal abnormalities that are critically
important to distinguishing among these processes: (1) reduction in GFR leading
to azotemia, (2) alterations of the urinary sediment and/or protein excretion, and

(3) abnormalities of urinary volume.
Table 45-1 Initial Clinical and Laboratory Data Base for Defining
Major Syndromes in Nephrology
Syndromes Important
Clues to Diagnosis
Findings
That Are
Common
Locati
on of
Discussion of
Disease-
Causing
Syndrome
Acute or
rapidly progressive
renal failure
Anuria
Oliguria
Documented
recent decline in GFR
Hypertensi
on, hematuria
Proteinuria
, pyuria
Casts,
edema
Chaps.
273, 277, 279,
283

Acute
nephritis
Hematuria,
RBC casts
Azotemia,
oliguria
Edema,
Proteinuria

Pyuria
Circulatory
congestion
Chap.
277
hypertension
Chronic renal
failure
Azotemia for
>3 months
Prolonged
symptoms or signs of
uremia
Symptoms or
signs of renal
osteodystrophy
Kidneys
reduced in size
bilaterally
Broad casts in
urinary sediment

Proteinuria
Casts
Polyuria,
nocturia
Edema,
hypertension
Electrolyte
disorders
Chaps.
272, 274
Nephrotic
syndrome
Proteinuria
>3.5 g per 1.73 m
2
per
Casts
Lipiduria
Chap.
277
24 h
Hypoalbumine
mia
Edema
Hyperlipidemi
a
Asymptomati
c urinary
abnormalities
Hematuria

Proteinuria
(below nephrotic
range)
Sterile pyuria,
casts
Chap.
277
Urinary tract
infection/pyelonephr
itis
Bacteriuria >10
5
colonies per
milliliter
Other
Hematuria
Mild
azotemia
Mild
Chap.
282
infectious agent
documented in urine
Pyuria,
leukocyte casts
Frequency,
urgency
Bladder
tenderness, flank
tenderness

proteinuria
Fever
Renal tubule
defects
Electrolyte
disorders
Polyuria,
nocturia
Renal
calcification
Large kidneys
Renal transport
Hematuria
"Tubular"
proteinuria (<1
g/24 h)
Enuresis
Chaps.
278, 279
defects
Hypertension Systolic/diastol
ic hypertension
Proteinuria
Casts
Azotemia
Chaps.
241, 280
Nephrolithias
is
Previous

history of stone
passage or removal
Previous
history of stone seen
by x-ray
Renal colic
Hematuria
Pyuria
Frequency,
urgency
Chap.
281
Urinary tract
obstruction
Azotemia,
oliguria, anuria
Polyuria,
Hematuria
Pyuria
Enuresis,
Chap.
283
nocturia, urinary
retention
Slowing of
urinary stream
Large prostate,
large kidneys
Flank
tenderness, full

bladder after voiding
dysuria
Note: GFR; glomerular filtration rate; RBC, red blood cell.