Urothelial carcinoma masquerading as retroperitoneal fibrosis: A case report.

Retroperitoneal fibrosis, a rare and often idiopathic condition, poses significant diagnostic challenges. While most cases are considered idiopathic or immune-mediated, a small but important proportion are associated with malignant neoplasms, with implications for prognosis and management. The present study describes the case of a 69-year-old man who presented to the emergency department of the Virgen de las Nieves University Hospital (Granada, Spain), with a 2-week history of epigastric pain, vomiting and altered bowel habits. Laboratory investigations revealed previously undiagnosed renal insufficiency. An abdominal computed tomography (CT) scan showed extensive diffuse retroperitoneal infiltration extending from the periduodenal region to the pubic bone, resulting in gastric dilatation and hydronephrosis. A CT-guided retroperitoneal biopsy was performed and pathology confirmed the presence of urothelial carcinoma. This diagnosis led to the initiation of a chemotherapy regimen consisting of carboplatin and gemcitabine specifically designed for urothelial carcinoma. A follow-up 18F-FDG PET scan performed 6 months later showed a partial functional response. This case illustrates a rare presentation of urothelial carcinoma masked by extensive retroperitoneal fibrosis, and highlights the importance of accurate diagnosis in reducing tumor burden and improving the clinical status of patients.