Duplex Kidney with Spontaneous Intraperitoneal Rupture of the Lower Moiety Pyonephrosis: An Extremely Rare Case Report

Introduction: Spontaneous intraperitoneal rupture of pyonephrosis is an extremely rare condition. It leads to generalized peritonitis that mimics an acute abdomen caused by intraperitoneal visceral pathology. In most cases, the underlying cause is obstructive urinary tract stones, followed by pelviureteric junction obstruction, tumors, or connective tissue diseases. We report the first case of spontaneous intraperitoneal fistulization of pyonephrosis from a duplex kidney. Case Presentation: A 56-year-old female presented with an acute abdomen and was diagnosed with a right incomplete duplex kidney and intraperitoneal rupture of lower renal moiety pyonephrosis secondary to an obstructive ureteric calculus located proximal to the confluence of the two ureters. She was successfully managed with initial percutaneous drainage and nephrostomy, followed by a delayed lower moiety nephrectomy. Conclusions: This case highlights the importance of considering renal etiology in the differential diagnosis of generalized peritonitis and underscores the rarity of such occurrences.