Percutaneous nephrolitotomy in bariatric surgery patients. Is there an increased risk of complications Introduction: To report a patient with a history of bariatric surgery and staghorn calculi of the left kidney, who had a colonic perforation after percutaneous renal surgery. Material and Methods: A 38 years old male patient, with a history of gastric bypass, underwent a left percutaneous nephrolithotomy due to staghorn renal calculi. In the procedure, the colon was incidentally perforated during the percutaneous access. Results: The patient developed a sepsis and fecal material appeared surrounding the nephrostomy tube. A transverse colostomy was performed, with improvement of the sepsis and a spontaneous resolution of the nephro-colonic fi stula. Conclusion: Is known that bariatric surgery is associated with the novo urinary lithiasis. Besides, there are anatomical changes in between intraabdominal viscera. Radiological studies and a adequate surgical strategy are fundamental to avoid severe surgical complications in kidney stone disease.