Bypass Pyeloplasty for Ureteropelvic Junction Obstruction Associated with Horseshoe Kidney: A Case Report.

INTRODUCTION: Horseshoe kidney (HSK) is the most common renal fusion and malrotation anomaly, and ureteropelvic junction obstruction (UPJO) due to high ureteral insertion (HUI) is frequently associated with HSK. Bypass pyeloplasty (BP) is a non-dismembered surgical technique involving a side-to-side anastomosis between the ureter just distal to the UPJO and the dependent portion of the hydronephrotic renal pelvis, and is suited for HUI. Although several procedures have been suggested for UPJO in HSK patients, BP has not been discussed much. In this case report, we describe the detailed procedure for BP successfully performed in an HSK patient with UPJO due to HUI.

CASE PRESENTATION: The patient was a girl aged 1 year and 10 months who had experienced intermittent abdominal pain and occasional vomiting for 1 month. She was diagnosed with dilation of the left renal pelvis and renal calyces (Society for Fetal Urology classification grade 3-4) on ultrasonography and subsequently referred to our hospital for diagnosis of left intermittent hydronephrosis. Renal scintigraphy revealed the HSK, and the differential renal function (DRF) in the left kidney was 16.3%. At 1 year and 11 months, she underwent retrograde left ureteropyelography and pyeloplasty. The retrograde left ureteropyelography showed the HUI and obstruction of the left ureter at approximately 45 mm from the cephalic edge of the umbilicus. We performed a 3.0-cm left flank incision to expose the left renal pelvis and ureter through the retroperitoneal route. HUI of the left ureter and crossing of a white cord-like structure that compressed the left ureter and renal pelvis just distal to the UPJO were identified. We divided the white cord-like structure and performed BP between the ureter just distal to the UPJO and the dependent portion of the renal pelvis. The postoperative course was good, with improvement in the renal pelvis dilation and the DRF in the left kidney. There has been no recurrence for >6 years after surgery.

CONCLUSIONS: We recommend BP as a physiological and suitable surgical approach that reduces the risk of impaired blood supply and postoperative anastomotic stenosis in HSK patients with UPJO due to HUI.