Sigmoid Kidney with Ureteropelvic Junction Obstruction in a Child: A Rare Pediatric Case Report

Abstract

Introduction: The sigmoid kidney is a rare form of crossed renal ectopia, in which the ectopic kidney is fused to the orthotopic kidney at its upper pole. This congenital anomaly is extremely uncommon. The purpose of this case report is to study the management of crossed renal ectopia, to discuss the surgical indications and prognostic features of this unusual malformative association. Case Presentation: We present the case of a 6-year-old girl who underwent surgery for ureteropelvic junction obstruction in the setting of a sigmoid kidney. A comprehensive workup was performed to evaluate the renal parenchyma and precisely assess the relative renal function. Results: A 6-year-old girl presented with acute abdominal pain. Abdominopelvic ultrasound followed by uro-MRI revealed an ectopic left kidney located anterolaterally and paraspinally on the right side, with malrotation. Its upper pole was fused with the lower pole of the right kidney, forming a sigmoid-shaped mass. There was significant left-sided pelvicalyceal dilatation. A left ureteropelvic junction obstruction was diagnosed, with a relative renal function estimated at 30%. A pyeloplasty was performed with placement of a double-J stent, and the postoperative course was uneventful. Conclusion: The sigmoid kidney is a rare congenital anomaly, often discovered incidentally, and frequently associated with ureteropelvic junction obstruction. Surgical management should be considered on a case-by-case basis, guided by periodic imaging and functional monitoring.