Abstract

Background: Retroperitoneal fibrosis (RPF) is a rare fibro-inflammatory disorder that can encase the abdominal aorta, inferior vena cava, and ureters. A mass-forming presentation may be difficult to distinguish from retroperitoneal malignancy.

Case presentation: A 55-year-old woman presented with abdominal discomfort, dysuria, and difficulty emptying her bladder. She had bilateral ureteral obstruction with hydronephrosis, an elevated serum creatinine (137.8 µmol/L), and normocytic anemia (hemoglobin 97 g/L), and bilateral percutaneous nephrostomies were placed. Contrast-enhanced computed tomography (CT) showed a lobulated periaortic and pericaval soft-tissue mass of approximately 91 × 23 × 41 mm, traversed by renal and mesenteric vessels and obscuring both ureters. Because malignancy could not be excluded, a laparoscopic retroperitoneal biopsy was performed. It showed fibroadipose tissue with inflammation, focal necrosis, hemorrhage, and a cluster of hyperchromatic cells. Lymphoma-directed immunohistochemistry was negative, and staging imaging, gynecological assessment, tumor markers, and lactate dehydrogenase revealed no primary malignancy. Antinuclear and antineutrophil cytoplasmic antibodies were negative. Serum IgG4 and IgG4 immunostaining were not available. Creatinine fell to 120.7 µmol/L after decompression, before immunosuppression was started. It reached 110.8 µmol/L after prednisolone and methotrexate were introduced, and spontaneous voiding returned before discharge. Follow-up CT about 5 months later showed a persistent lesion (94 × 18 × 37 mm) without significant interval change.

Conclusions: The lesion’s distribution, the obstructive uropathy, and the fibro-inflammatory histology.

This case highlights the need for a complete histopathological work-up, including IgG4 and carcinoma markers, and for long-term renal and radiological surveillance.