Infiltrative retroperitoneal metastasis causing obstructive uropathy and gastric outlet obstruction secondary to an occult sigmoid colon adenocarcinoma: a rare case report and literature review
Year: 2026
Type: article
Study design: Case Report
Abstract: Introduction: Colorectal cancer most often presents with gastrointestinal problems such as obstruction and abdominal pain, or is detected early by screening colonoscopy. Retroperitoneal metastasis that mimics the findings of retroperitoneal fibrosis is rare and can cause diagnostic challenges, especially in patients in whom contrast-enhanced imaging is contraindicated. Case presentation: A 49-year-old woman was admitted with severe bilateral flank pain, oliguria, intermittent nausea, and loss of appetite without abdominal distention or constipation. Due to a known allergy to contrast media, a non-contrast CT scan was performed and showed bilateral hydronephrosis and evidence of retroperitoneal fibrosis. Although double-J ureteral stents were inserted, the patient's renal function progressively deteriorated, requiring hemodialysis. After that, the patient experienced intractable vomiting, and the evaluation confirmed gastric outlet obstruction (GOO) caused by mass effect from a retroperitoneal mass. Magnetic resonance imaging findings continued to favor retroperitoneal fibrosis despite the presence of some suspicious pulmonary nodules. Surgical intervention with retroperitoneal biopsy was performed, during which an incidental sigmoid mass was detected and resected. Histopathology revealed well-differentiated sigmoid adenocarcinoma with retroperitoneal metastasis. Discussion: Malignancy-associated retroperitoneal fibrosis faces critical diagnostic challenges due to its radiologic findings that can mimic a benign fibroinflammatory process. Unlike previous reports that focus on retroperitoneal fibrosis in patients with known primary malignancies, this case presented without a history or symptoms of colorectal cancer. Additionally, the inability to perform a contrast-enhanced CT scan contributed to a delayed diagnosis. Failure of ureteral stenting and GOO symptoms were two main indicators of infiltrative malignant disease. Timely tissue diagnosis remains essential for atypical manifestations of retroperitoneal fibrosis. Conclusion: . Timely diagnosis and intervention require interdisciplinary collaboration to achieve critical, life-saving outcomes.
Institutions: Shiraz University, Shiraz University of Medical Sciences
Language: English
Subfield: Pulmonary and Respiratory Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,090
OpenAlex ID: W7225719317