Obstructive Uropathy

Obstruction to urine flow can occur anywhere in the urinary tract. Proximal to the obstruction, pressures within the collecting system and renal tubules will rise. Ultimately, renal injury will result because of cellular atrophy and necrosis if the obstruction to urine flow is not relieved. Acute obstruction will produce distention of the bladder, ureter, or renal pelvis that is generally associated with pain. However, a slowly progressing obstruction can result in massive dilatation of the collecting system with no clinical symptoms. Recovery of some renal function can generally be expected in cases of complete unilateral ureteral obstruction if flow is restored within 6 weeks.

CAUSES OF OBSTRUCTION

The most frequent causes of obstruction in adult males are stones, benign prostatic hyperplasia, prostate cancer, ureteropelvic junction (UPJ) obstruction, and ureteral strictures, whereas in females the most frequent causes are pregnancy, stones, UPJ obstruction, pelvic malignancies, and surgical trauma to the ureters. In children, UPJ obstruction, ureterovesical junction obstruction (e.g., ectopic ureters), ureteroceles, urethral valves, and stones are most frequently responsible for urinary obstruction.

Causes of obstruction can be more systematically evaluated by location.

▪ Bladder Outlet Obstruction

Mechanical	Functional
Benign prostatic hyperplasia	Neurogenic (detrusor-sphincter dyssynergia)
Urethral stricture	Pharmacologic
Bladder neck contracture
Posterior urethral valves
Ureteroceles
Urethral stone
Foreign body

▪ Ureteral Obstruction

Intrinsic Obstruction	Extrinsic Obstruction
Stones	Pregnancy
Tumors	Tumor
Strictures (tuberculosis, radiation, previous instrumentation)	Retroperitoneal fibrosis
Adynamic segment at UPJ	Crossing blood vessel to lower pole of kidney (UPJ)
	Retrocaval ureter
	Pelvic lipomatosis
	Iatrogenic ligature

DIAGNOSIS

The diagnosis of lower urinary tract obstruction must always be the first consideration in the patient who presents with oligoanuria. The simple passage of a urethral catheter or percutaneous suprapubic catheter is both diagnostic and therapeutic. Upper urinary tract obstruction will require more specialized diagnostic techniques.

Renal Ultrasound

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