Can retroperitoneal fibrosis cause rectal polyps?

Can Retroperitoneal Fibrosis Cause Rectal Polyps?

No, retroperitoneal fibrosis (RPF) does not cause rectal polyps. These are distinct pathological entities with completely different etiologies and mechanisms.

Key Distinction Between RPF and Rectal Polyps

Retroperitoneal fibrosis is a fibro-inflammatory process affecting the retroperitoneum, not a polyposis syndrome. RPF is characterized by proliferation of aberrant fibroinflammatory tissue that typically surrounds the infrarenal abdominal aorta, inferior vena cava, and iliac vessels 1. This process may extend to neighboring structures and frequently entraps the ureters, but it does not produce mucosal polyps in the gastrointestinal tract 2, 3.

What RPF Actually Affects

RPF can cause rectal symptoms through mechanical compression, not through polyp formation:

• Rectal compression: In rare atypical presentations, RPF can extend below the pelvic rim and compress the rectum from outside, causing constipation and mimicking a rectal tumor on imaging 4
• Retrorectal fibrosis: One case report documented retrorectal fibrosis compressing the rectum and ureter, presenting with constipation as the chief complaint, but this was external compression, not polyp formation 4
• Pelvic involvement: Approximately 40% of RPF cases may present in atypical locations including the pelvis, but this represents fibrotic tissue in the retroperitoneum, not intraluminal polyps 3

Actual Causes of Rectal Polyps

Rectal polyps arise from completely different mechanisms:

• Hereditary polyposis syndromes: Including familial adenomatous polyposis (FAP), juvenile polyposis, Peutz-Jeghers syndrome, and MYH polyposis, all caused by specific genetic mutations affecting mucosal epithelium 2
• Sporadic adenomas: Arising from epithelial dysplasia without underlying genetic syndromes 5
• Inflammatory polyps: Associated with inflammatory bowel disease 2

Clinical Pitfall to Avoid

Do not confuse external compression of the rectum by RPF with true rectal polyps. If a patient with known RPF develops rectal symptoms:

• Imaging may show a mass effect on the rectum that could be mistaken for an intraluminal lesion 4
• Endoscopy is essential to differentiate external compression (smooth, intact mucosa) from true polyps (mucosal lesions) 4
• Biopsy may be necessary to rule out malignancy, as malignant RPF accounts for up to 10% of cases and can mimic benign disease 1

When RPF and Polyps Coexist

If a patient has both RPF and rectal polyps, these are coincidental findings requiring separate evaluation and management:

• The polyps should be managed according to standard polyposis guidelines with surveillance colonoscopy 5
• The RPF requires separate treatment with corticosteroids as first-line therapy and monitoring with cross-sectional imaging 6, 2