Abstract
RATIONALE: Spontaneous rupture of the urinary bladder (SRUB) is a rare, easily missed cause of urinary ascites that mimics intrinsic renal failure through peritoneal reabsorption of urinary solutes ("reverse peritoneal dialysis"). Rapid recognition prevents unnecessary dialysis and life-threatening complications. This case underscores key diagnostic pointers (especially the ascites/serum creatinine (SCr) ratio and the decisive role of computed tomography [CT] cystography). PATIENT CONCERNS: A previously healthy 45-year-old man presented 5 days after heavy alcohol intake with severe lower-abdominal pain, progressive abdominal distension, oliguria (~300 mL/24 hours), and dyspnea. Initial tests showed SCr 7.6 mg/dL, blood urea nitrogen 108 mg/dL, sodium 125 mmol/L, and potassium 6.0 mmol/L. DIAGNOSES: Ascitic fluid analysis revealed creatinine 131 mg/dL with an ascites/SCr ratio of ~17:1, indicating urinary ascites. Retrograde CT cystography demonstrated intraperitoneal contrast extravasation from the right bladder wall, confirming SRUB with pseudo-acute kidney injury. INTERVENTIONS: Initial hemodialysis and large-volume paracentesis (2.0-2.5 L/day) did not improve distension. A Foley catheter was placed, CT cystography was performed, and the patient underwent surgical bladder repair with urinary ascites evacuation and postoperative bladder drainage. OUTCOMES: Urine output increased promptly. Electrolytes and SCr normalized within 48 hours after repair. A day-7 cystogram showed no leak; the catheter was removed at 3 weeks. At 3-month follow-up, there was no recurrence. LESSONS: Consider SRUB in patients with unexplained ascites, oliguria, and acute azotemia (particularly after alcohol binge drinking). Measuring the ascites/SCr ratio (>2) provides powerful evidence of urinary ascites, and CT cystography is the preoperative diagnostic gold standard. Early definitive repair reverses electrolyte derangements rapidly and avoids unnecessary renal replacement therapy and potential fatal peritonitis.