Bladder rupture is associated with "pseudorenal failure," in which the urine is reabsorbed from the peritoneum, resulting in increased serum blood urea nitrogen (BUN) and creatinine levels. We report a case of ruptured bladder with pseudorenal failure. An 80 -yearold woman with a history of ovarian cancer surgery visited her previous physician with complaints of mild lower abdominal pain and abdominal distention. On admission, serum BUN and creatinine levels were elevated, but they improved promptly after insertion of an indwelling urethral catheter. Contrastenhanced computed tomography (CT) scan did not reveal any specific findings other than ascites effusion, so the diagnosis of bladder rupture could not be made preoperatively. Unexplained ascites effusion and unexplained elevation of serum BUN and creatinine levels may indicate a ruptured bladder with pseudorenal insufficiency. Contrastenhanced examination is useful for the diagnosis of bladder rupture, but reevaluation of renal function with cystatin C and insertion of an indwelling urethral catheter as diagnostic treatment may also be useful.