hydronephrosis /hī′drōnefrō″sis/ [Gk, hydor + nephros, kidney, osis, condition] , distension of the pelvis and calyces of the kidney by urine that cannot flow past an obstruction in a ureter. Ureteral obstruction may be caused by a tumor, a calculus lodged in the ureter, inflammation of the prostate gland, or edema caused by a urinary tract infection. Symptoms include pain in the flank and, in some cases, hematuria, pyuria, and hyperpyrexia. IV pyelography, cytoscopy, or retrograde pyelography may be used in diagnosis. Surgical repair or removal of the obstruction may be necessary. Prolonged hydronephrosis causes atrophy and eventual loss of kidney function. Also called ureterohydronephrosis. See also urinary calculus. −hydronephrotic, adj.
