C h a p t e r 2 5
Disorders of Renal Function
631
Obstructive Disorders
Urinary obstruction can occur in persons of any age
and can involve any level of the urinary tract, from the
urethra to the renal pelvis
5,27
(Fig. 25-13). Obstruction
may be sudden or insidious, partial or complete, and
unilateral or bilateral. The conditions that cause urinary
tract obstruction include congenital anomalies, urinary
calculi (i.e., stones), pregnancy, benign prostatic hyper-
plasia, scar tissue resulting from infection and inflam-
mation, tumors, and neurologic disorders such as spinal
cord injury. The causes of urinary tract obstructions are
summarized in Table 25-1.
Obstructive uropathy is usually classified according
to site, degree, and duration of obstruction. Lower uri-
nary tract obstructions are located below the ureteroves-
ical junction and are bilateral in nature. Upper urinary
tract obstructions are located above the ureterovesical
junction and are usually unilateral. The condition caus-
ing the obstruction can cause complete or partial occlu-
sion of urine outflow. When the obstruction is of short
duration (i.e., less than a few days), it is said to be acute
and is usually caused by conditions such as renal calculi.
An obstruction that develops slowly and is longer last-
ing is said to be chronic and is usually caused by con-
ditions such as congenital ureterovesical abnormalities.
Bilateral acute urinary tract obstruction causes acute
renal failure. Because many causes of acute obstruction
are reversible, prompt recognition is important. When
left untreated, an obstructed kidney undergoes atro-
phy, and in the case of bilateral obstruction, results in
chronic kidney disease.
SUMMARY CONCEPTS
■■
Tubulointerstitial diseases affect the tubules
and the surrounding interstitium of the kidneys.
These disorders include acute and chronic
pyelonephritis and the effects of drugs and
toxins. Pyelonephritis, or infection of the kidney
and kidney pelvis, can occur as an acute or a
chronic condition. Acute pyelonephritis typically
is caused by ascending bladder infections or
infections that come from the bloodstream; it
usually is successfully treated with appropriate
antimicrobial drugs. Chronic pyelonephritis is a
progressive disease that produces scarring and
deformation of the renal calyces and pelvis.
■■
The susceptibility of the kidney to drug-induced
damage reflects its significant exposure to
medications and their metabolites. Some
drugs, such as diuretics, high–molecular-weight
radiocontrast media, the immunosuppressive
drugs cyclosporine and tacrolimus, and the
NSAIDs can cause acute prerenal failure by
decreasing renal blood flow. Other drugs such
as sulfonamides and vitamin C can form crystals
that cause kidney damage by obstructing urinary
flow in the tubules. Drugs can also directly
damage tubulointerstitial structures, or provoke
hypersensitivity reactions. Illicit drug use has also
been implicated in a wide spectrum of kidney
diseases.
Pregnancy
or tumor
Uretero-
vesical
junction
stricture
Kidney
stone
Scar
tissue
Neurogenic
bladder
Bladder
outflow
obstruction
FIGURE 25-13.
Locations and causes of urinary tract
obstruction.
TABLE 25-1
Causes of UrinaryTract Obstruction
Level of Obstruction Cause
Renal pelvis
Renal calculi
Papillary necrosis
Ureter
Renal calculi
Pregnancy
Tumors that compress the
ureter
Ureteral stricture
Congenital disorders of the
uretero-vesical junction
and ureteropelvic junction
strictures
Bladder and urethra
Bladder cancer
Neurogenic bladder
Bladder stones
Prostatic hyperplasia or
cancer
Urethral strictures
Congenital urethral defects
