Severe anemia and melena caused by pyeloduodenal fistula due to renal stone-associated squamous cell carcinoma

Pyeloduodenal fistula is a rare condition and its association with malignancy is even rarer. Herein we report the case of a 66-year-old man who was admitted to the hospital with a three-month history of intermittent melena and a more than 20-year history of right-side renal stones. Computed tomography showed a heterogeneous right renal mass with a staghorn stone that had invaded the duodenum and caused an internal fistula. An upper gastrointestinal series showed pyeloduodenal fistula. The patient underwent an exploratory operation and a biopsy was taken at the peripelvic region. Pathological examination verified the existence of squamous cell carcinoma. To our knowledge, this is the first case of pyeloduodenal fistula associated with renal stones, squamous cell carcinoma and upper urinary tract calculus presenting on melena. We report on the features of this rare entity but also review and summarize the etiology, diagnosis and treatment options that can be extrapolated from the existing literature.