Obstructive uropathy occurs when the flow of urine from the kidneys is blocked. This causes the kidneys to dilate and become damaged. Obstruction can occur anywhere in the the urinary system. If the obstruction is bilateral (affecting both kidneys), bladder outlet obstruction is the most common cause. The kidneys produce urine in the normal manner but the urine cannot leave the bladder because it is blocked. Urine may back up behind this obstruction and cause damage to the structures of the urinary tract.
When the obstruction causes urine to back up into both kidneys, hydronephrosis (swelling of the kidneys) results. If both kidneys are affected, this can eventually lead to hypertension and/or renal failure. Sudden blockage causes acute bilateral obstructive uropathy, while slow, progressive blockage causes chronic bilateral obstructive uropathy.
Chronic bilateral obstructive uropathy is caused by gradual blockage of both ureters (the tubes between the kidneys and the bladder), the bladder, or the urethra, resulting in a backup of urine into both kidneys. In men, this is most often as a result of a benign enlargement of the prostate (BPH). Bladder outlet obstruction is much less common in women but can be caused by a bladder cystocele.
Other causes include bladder tumors, prostate tumors, and tumors or masses of the uterus or other structures around the bladder neck or urethra, including retroperitoneal fibrosis. Narrowing of the urethra may also cause obstruction secondary to a congenital (present from birth) deformity or scar tissue from injury or infection.
Initially, the bladder reacts to the obstruction by increased irritability. There is a stronger and more frequent urge to urinate, and bladder spasms or incontinence may occur. As urine accumulates and the bladder fails to empty completely (urine stasis), urinary tract infections may occur. Symptoms are the result of urinary retention and damage to the bladder, ureters, and kidneys.
Chronic bilateral obstructive uropathy occurs in about 1 out of every 1,000 people.
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