A 54-year-old woman—with no past surgical history—presented to the emergency department with an 8-day history of abdominal pain in the left flank and diarrhea. Initially, the patient underwent an abdominal ultrasound that showed a lower pole kidney mass. Computed tomography was performed and revealed a fragmented staghorn calculus complicated with a xanthogranulomatous pyelonephritis in the left kidney (Fig. 1). The cleavage plane between the left kidney and the colon was undistinguished and a nephrocolic fistula (arrows) was diagnosed. To confirm this finding a barium enema was carried out: demonstrating passage of intravenous contrast from the colon to the kidney. Finally, the patient was taken to the surgery room where nephrectomy and left hemicolectomy were carried out.

Fig. 1
figure 1

Abdominal computed tomography. Axial view of the abdomen demonstrating the nephrocolic fistula (arrows) and the presence of a staghorn calculus

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Few nephrointestinal fistulae have been described in the literature, and the cases of spontaneous appearance of this condition are even scarce [1]. The most common cause of spontaneous nephrocolic fistulae involves staghorn calculi [2]. These calculi are formed of a rapidly growing stone and are mainly composed of struvite–carbonate–apatite matrix. These stones are likely to cause great morbidity and mortality if not treated. Treatment frequently includes: percutaneous nephrolithotomy, followed by extracorporeal shock wave lithotripsy and/or flexible ureteroscopy, and laser [3]. Imaging procedures—abdominal X-rays and computed tomography—are the best diagnostic tools to be used in this condition.