Urinary Tract Obstruction



Obstruction to urine flow may occur at any point from the renal pelvis to the urethral meatus. The causes of obstruction are manifold but may be classified into a few general groups, as given in Table 34-6. The age and sex of the patient ob­viously influence the likelihood of a given pairing of etiology and site.

The obstruction may occur suddenly, as with a lodged calculus, and be associated with flank and radiating groin pain; or occur slowly, as with compression by cervical carcinoma, and be as­sociated with no symptoms until uremia from renal failure appears. So long as urine formation proceeds, the urinary tract proximal to the ob­struction dilates (hydronephrosis). However, long-standing obstruction causes tubular and in-terstital atrophy and eventual glomerular scle­rosis, and urine formation ceases. Urinary tract dilation may no longer be evident at that time.

A change in urinary habits is often the pre­senting sign of urinary tract obstruction. Complete urinary tract obstruction is the most common cause of true anuria. However, polyuria, es­pecially nocturia, is not uncommon in partial obstruction and may occur as a consequence of defective urinary concentration. Overflow in­continence is a common occurrence in lower tract obstruction.
Unilateral ureteral obstruction usually causes no detectable change in urinary flow nor in total.