Assessing the Role of Flexible Sigmoidoscopy for Patients With Positive Fecal Immunochemical Test (FIT) and Rectal Bleeding as a Sole Symptom Within the Fast-Track Pathway.

Background Rectal bleeding is a frequent symptom, with causes ranging from benign conditions to serious diseases like colorectal cancer (CRC) and inflammatory bowel disease (IBD). In the UK, the two-week wait (2WW) referral pathway, which includes the fecal immunochemical test (FIT), plays a key role in triaging suspected CRC cases. This study evaluates the effectiveness of flexible sigmoidoscopy (FS) in detecting significant bowel pathologies (SBPs) in FIT-positive patients with isolated rectal bleeding. Methods We reviewed records of 344 patients with isolated rectal bleeding and a positive FIT result, referred to the 2WW pathway at York and Scarborough Teaching Hospitals NHS Foundation Trust from February to December 2023. All patients underwent colonoscopy. Findings from colonoscopy were used as a standard to compare with the expected reach of FS. Pathologies were categorized into SBPs (cancer, IBD, polyps ≥10 mm) and non-SBPs, and the location of SBPs in relation to the splenic flexure was also assessed. Results The average age of patients was 61.58 years. Significant bowel pathology (SBP) was identified in 89 of 344 (25.9%) patients, including 16 (18%) patients with cancer, 21 (23.6%) patients with IBD, and 52 (58.4%) patients with large polyps. All cases of cancer and IBD were found distal to the splenic flexure, while 21.1% (11/89) of large polyps were proximal. Higher FIT values (>100 µg Hb/g feces) and older age were significantly associated with SBPs. However, age and higher FIT values did not predict whether SBPs were proximal or distal. Conclusion For FIT-positive patients with isolated rectal bleeding, FS can serve as an effective initial diagnostic tool. Patients without detected cancer can be downgraded from the fast-track pathway to routine colonoscopy follow-up to avoid missing proximal premalignant lesions. This approach enhances resource utilization while ensuring comprehensive patient care. Further studies are needed to improve triage criteria and diagnostic accuracy within the 2WW pathway.