A case of acute kidney injury due to secondary retroperitoneal fibrosis caused by direct invasion of esophageal squamous cell carcinoma.

A 71-year-old man who developed renal failure was admitted to our hospital. Computed tomography without contrast enhancement showed bilateral hydronephrosis together with a soft tissue mass around the abdominal aorta, leading to the diagnosis of retroperitoneal fibrosis. Serum levels of immunoglobulin G4 were within the normal range. The patient was then evaluated for the presence of undiagnosed malignancy as a possible cause of secondary retroperitoneal fibrosis. Upper gastrointestinal tract endoscopy demonstrated esophageal cancer. Histology of the esophageal lesion and the retroperitoneal mass showed squamous cell carcinoma (SCC). Therefore, the retroperitoneal fibrosis was considered to be due to the invasion of SCC of the esophagus, and chemotherapy was chosen as the treatment. This is the first case report of postrenal failure due to secondary retroperitoneal fibrosis caused by the direct invasion of esophageal SCC. Physicians should be aware of occult malignancy as the cause of unexplained retroperitoneal fibrosis, even clinically silent, to avoid inappropriate management or delay in the treatment of potentially life-threatening co-morbidities.