Synopsis
Recognise colorectal cancer across symptomatic, screening and emergency presentations, investigate without false reassurance, and coordinate stage-specific multidisciplinary treatment and surveillance safely.
- Right-sided cancers often present with iron-deficiency anaemia, fatigue, weight loss or a mass; left-sided lesions more often produce altered bowel habit, bleeding or obstruction.
- Rectal cancer may cause bright bleeding, tenesmus, urgency, incomplete evacuation or a palpable lesion on digital rectal examination.
- In symptomatic adults, quantitative FIT supports referral decisions, but a rectal or abdominal mass, obstruction, persistent unexplained symptoms or strong clinical concern must override a reassuring result.
- The symptomatic NICE referral threshold and the NHS bowel-screening threshold serve different populations and must never be interchanged; screening policy also varies between UK nations.
- Colonoscopy with biopsy usually establishes diagnosis; CT colonography is an alternative when colonoscopy is unsuitable or incomplete but cannot provide tissue.
- Stage with CT chest, abdomen and pelvis; add high-resolution pelvic MRI for rectal cancer and discuss every confirmed case at a specialist colorectal MDT.
- Test colorectal tumours for mismatch-repair deficiency or microsatellite instability because results affect Lynch syndrome assessment, prognosis and selected systemic treatment.
- CEA is useful as a baseline and for selected follow-up, but a normal value neither excludes cancer nor makes surveillance imaging unnecessary.
Key red flags
Tenesmus, urgency, mucus, bleeding and a sense of incomplete evacuation should prompt inspection and digital rectal examination where appropriate, with urgent referral even if FIT is low when a mass is felt.
Absolute constipation, vomiting, marked distension, peritonism, fever, shock or free air indicate an oncological surgical emergency; closed-loop caecal dilatation can perforate remotely from a distal tumour.
Hepatomegaly, jaundice, ascites, respiratory symptoms, bone pain, cachexia or venous thromboembolism may be the first clue to advanced disease and require prompt staging rather than symptom-only treatment.
Investigation priorities
Triage eligible symptomatic people into the colorectal cancer pathway.
Management branches
New colorectal symptoms, unexplained iron deficiency, or a concerning examination finding.
- Take a site-focused history, examine the abdomen, inspect the anus where relevant and perform digital rectal examination for rectal symptoms when clinically appropriate.
- Request quantitative FIT according to the current symptomatic pathway, plus blood count and iron studies, without allowing testing logistics to delay referral for a mass, obstruction or marked concern.
- Refer on the applicable suspected-cancer pathway when criteria are met; document what happens after a low result and arrange active review if symptoms persist or evolve.
- Use colonoscopy with biopsy or CT colonography as selected by the diagnostic service, then stage confirmed cancer and present it to the colorectal MDT.