Teaching Case

A rare case of pyeloduodenal fistula diagnosed on contrast swallow. Pyeloenteric fistulas between the upper urinary tract and the gastrointestinal system are rare. They are usually between the right renal pelvis and the duodenum and are classified as spontaneous or traumatic. Approximately 80% are spontaneous and almost 65% of spontaneous renal fistulas are secondary to nephrolithiasis . Other rare causes include malignancy and inflammatory processes, i.e. crohn’s disease and diverticular disease.

A 74 years old lady was admitted following a short history of swollen painful left leg. Extensive deep vein thrombosis of the left femoral and popliteal veins was diagnosed on Doppler U/S. Prior to her admission, she was shortly due to see the gastroenterologist for a 6-7 weeks history of two stone weight loss, decreased appetite, constipation and a palpable, right abdominal mass. She was investigated with contrast enhanced abdominal CT which showed a large right sided retroperitoneal necrotic mass with invasion of the duodenum, IVC and right renal pelvis causing gross hydronephrosis (see Fig.1 a,b). During her admission she developed an upper gastrointestinal bleed. An OGD was performed which demonstrated an ulcerating tumour causing obstruction of the proximal duodenum. Biopsies were taken and confirmed squamous cell carcinoma. Water soluble contrast swallow was performed to assess gastric outflow. This demonstrated dilated stomach with contrast pooling in the body and fundus and no contrast passage beyond the proximal duodenum. Contrast extravasation was seen to track into the right renal pelvis and to a localized irregular cavity in the right paraspinal region indicating a fistula formation between the duodenum and the right kidney and the previously described retroperitoneal tumour (see Fig.2 a,b).

The kidneys and associated structures are normally separated from the enteric system by the peritoneum, Gerota facia and perirenal fat hence pyeloenteric fistulas tend to occur where these structures are attenuated or absent ³. As the duodenum abuts the right kidney medially and anteriorly, it is therefore susceptible to fistula formation with the kidney. Meyers ⁴ and Underwood ⁵ reported that atrophy of the perinephric fat was necessary for the development of pyeloenteric fistulas. However pyeloduedenal fistulae appear to develop without perinephric fat atrophy as demonstrated in our patient. There are various imaging modalities that may help to establish the diagnosis of pyeloduodenal fistulas. Sixty percent of pyeloduodenal fistulas involving a functioning kidney are diagnosed by Intravenous urography⁶. Retrograde pyelogram may be used in a non-functioning kidney. Upper GI contrast studies have also been used to demonstrate pyeloduodenal fistula as it was in our patient. CT scan is helpful in identifying the underlying pathology or air collection in the collecting systems. Surgical intervention remains the definitive treatment. Prognosis for benign processes is generally good if diagnosed early and is not associated with sepsis. However, fistulas caused by advanced malignancy carry a poor prognosis mainly due to the malignant process itself ³.