Atlas of pathophysiology, 2 Edition

Part II - Disorders


Hydronephrosis is an abnormal dilation of the renal pelvis and the calyces of one or both kidneys, caused by an obstruction of urine flow in the genitourinary tract. Although partial obstruction and hydronephrosis may not produce symptoms initially, the pressure built up behind the area of obstruction eventually results in symptomatic renal dysfunction.

Age Alert

Hydronephrosis may be detected by prenatal ultrasound. Postnatal follow-up is critical if surgery is indicated.


·   Almost any type of obstructive uropathy

·   Most common:

§  benign prostatic hyperplasia

§  urethral strictures

§  calculi

·   Less common:

§  strictures or stenosis of the ureter or bladder outlet

§  congenital abnormalities

§  trauma

§  abdominal tumors

§  blood clots

§  neurogenic bladder


If obstruction is in the urethra or bladder, hydronephrosis is usually bilateral; if obstruction is in a ureter, it's usually unilateral. Obstructions distal to the bladder cause the bladder to dilate and act as a buffer zone, delaying hydronephrosis. Total obstruction of urine flow with dilation of the collecting system ultimately causes complete cortical atrophy and cessation of glomerular filtration.

Signs and symptoms

Clinical features of hydronephrosis vary with the cause of the obstruction.

·   No symptoms, or mild pain and slightly decreased urinary flow

·   Severe, colicky renal pain or dull flank pain that may radiate to the groin

·   Gross urinary abnormalities, such as hematuria, pyuria, dysuria, alternating oliguria and polyuria, or complete anuria

·   Nausea, vomiting, abdominal fullness, pain on urination, dribbling, hesitancy

Diagnostic test results

·   Renal function blood studies are abnormal.

·   Urine studies confirm the inability to concentrate urine, decreased glomerular filtration rate, and pyuria if infection is present.

·   Excretory urography, retrograde pyelography, and renal ultrasound confirm the diagnosis.

·   I.V. urogram detects the site of obstruction.

·   Nephrogram shows delayed appearance time.

·   Radionuclide scan shows the site of obstruction.


·   Ureteral stent or nephrostomy tube

·   Surgical removal of the obstruction:

§  dilation for stricture of the urethra

§  prostatectomy for benign prostatic hyperplasia

·   With renal damage: diet low in protein, sodium, and potassium to slow progression before surgery

·   Inoperable obstructions: decompression and drainage of kidney through temporary or permanent nephrostomy tube in the renal pelvis

·   Concurrent infection: appropriate antibiotic therapy





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