Retrograde ureteroscopic lithotripsy in cross‐fused renal ectopia

INTRODUCTION: Cross‐fused renal ectopia is a rare congenital malformation, and few cases of urolithiasis have been treated by retrograde ureteroscopic lithotripsy. We report a case of urolithiasis in right‐to‐left and superior‐type cross‐fused renal ectopia, successfully treated by the retrograde approach. CASE PRESENTATION: A 69‐year‐old woman with two 14‐mm renal stones in cross‐fused renal ectopia underwent retrograde ureteroscopic lithotripsy. Although we did not recognize the anomaly preoperatively, we could diagnose urolithiasis in the ectopic kidney intraoperatively. The patient had no complication, and follow‐up computed tomography after 3 months showed only a 5‐mm renal stone. CONCLUSION: Although urolithiasis in patients with cross‐fused renal ectopia is a challenging condition for the urologist, the retrograde approach is a safe and effective treatment method. It is necessary to carefully examine the urinary tract especially in a patient with a history of unidentified solitary kidney.