Hydronephrosis
An abnormal dilation of the renal pelvis and the calyces of one or both kidneys, hydronephrosis is 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.
Causes
Almost any type of obstructive uropathy can result in hydronephrosis. The most common causes are benign prostatic hyperplasia (BPH), urethral strictures, and calculi; less common causes include strictures or stenosis of the ureter or bladder outlet, congenital abnormalities, abdominal tumors, blood clots, neurogenic bladder, and tumors of the ureter and bladder.
Sites of obstruction
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.
