4.2 Lower Gastrointestinal Bleeding, IBD & Colorectal Malignancy
Key Takeaways
Lower gastrointestinal bleeding originates distal to the ligament of Treitz; common aetiologies include diverticular disease (most common cause of acute painless brisk bleed), angiodysplasia, haemorrhoids, and colorectal neoplasia.
Ulcerative colitis causes continuous, mucosal-submucosal inflammation extending proximally from the rectum with crypt abscesses and pANCA positivity; Crohn's disease causes patchy, transmural inflammation with skip lesions, non-caseating granulomas, and fistulae.
Acute severe ulcerative colitis is defined by the Truelove and Witts criteria (≥6 bloody stools/day plus at least one systemic toxicity sign); immediate treatment is IV hydrocortisone 100 mg QDS with prophylactic LMWH for VTE prevention.
Day 3 Travis (Oxford) criteria (stool frequency >8/day or CRP >45 mg/L) predict an 85% colectomy rate and mandate immediate escalation to rescue therapy with infliximab or ciclosporin.
Under NICE NG12 (2023), symptomatic adults such as those with a change in bowel habit or iron-deficiency anaemia are offered FIT, and a result of 10 µg Hb/g or more triggers suspected colorectal cancer pathway referral.
Lower Gastrointestinal Bleeding, IBD & Colorectal Malignancy
Lower gastrointestinal bleeding (LGIB) refers to intraluminal blood loss arising distal to the ligament of Treitz, predominantly originating from the colon, rectum, or anal canal. While approximately 80% of LGIB episodes resolve spontaneously with supportive measures, acute severe bleeding and chronic occult blood loss present vital diagnostic challenges spanning inflammatory bowel disease (IBD) and colorectal malignancy.
1. Aetiology & Clinical Evaluation of Lower GI Bleeding
Clinical evaluation hinges on characterizing the nature of blood passed:
- Haematochezia: Fresh bright red or maroon blood passed per rectum; indicates colonic, rectal, or anal bleeding (or massive upper GI haemorrhage).
- Blood Mixed with Stool: Suggestive of colonic source, inflammatory bowel disease, or carcinoma.
- Blood Coating Surface of Stool / On Toilet Paper: Characteristic of anorectal pathology (haemorrhoids, anal fissures).
| Aetiology | Frequency | Pathophysiology & Clinical Presentation |
|---|---|---|
| Diverticular Disease | ~30–40% | Rupture of mucosal vasa recta stretched over the dome of an acquired colonic diverticulum. Typically presents as sudden-onset, painless, brisk, bright red or maroon bleeding. More common in right-sided diverticula despite left-sided preponderance. ~80% resolve spontaneously. |
| Haemorrhoids & Fissures | ~15–20% | Dilated submucosal arteriovenous plexuses (haemorrhoids) or linear mucosal tears at the anoderm (fissures). Haemorrhoids cause painless bright red bleeding coating stool; fissures produce excruciating tearing pain on defecation with minor bleeding. |
| Angiodysplasia | ~5–10% | Degenerative tortuous submucosal arteriovenous malformations, most common in the caecum and ascending colon of elderly patients. Associated with aortic stenosis (Heyde's syndrome) due to shear-stress depletion of von Willebrand factor multimers, and end-stage renal disease. Intermittent, painless bleeding. |
| Colitis (IBD / Ischaemic / Infectious) | ~15–20% | Mucosal ulceration presenting with bloody diarrhoea, abdominal cramps, and tenesmus. Ischaemic colitis occurs in physiological watershed zones (Griffiths' point at the splenic flexure and Sudeck's point at the rectosigmoid junction) following transient systemic hypotension. |
| Colorectal Carcinoma & Polyps | ~10–15% | Insidious, chronic occult blood loss leading to iron deficiency anaemia, intermittent visible rectal bleeding, and altered bowel habit in patients >50 years. |
Clinical Risk Stratification: The Oakland Score
The British Society of Gastroenterology recommends the Oakland Score to identify patients with acute lower GI bleeding who are at low risk of adverse outcomes (rebleeding, transfusion, therapeutic intervention, or death). An Oakland score ≤8 points defines safe outpatient discharge, whereas scores >8 warrant hospital admission and inpatient colonoscopy.
2. Inflammatory Bowel Disease: Ulcerative Colitis vs Crohn's Disease
Inflammatory bowel disease comprises two distinct chronic idiopathic relapsing-remitting inflammatory disorders: Ulcerative Colitis (UC) and Crohn's Disease (CD).
| Clinical Feature | Ulcerative Colitis (UC) | Crohn's Disease (CD) |
|---|---|---|
| Anatomical Distribution | Confined to the colon and rectum; strictly continuous disease commencing at the rectum (proctitis) and extending proximally without gaps. Backwash ileitis may rarely occur. | Affects any part of the GI tract from mouth to anus ("gum to bum"); terminal ileum and caecum affected in >50%; characterized by discontinuous skip lesions. |
| Depth of Inflammation | Mucosal and submucosal only. Serosa and muscularis propria are spared (except in toxic megacolon). | Transmural (full thickness of bowel wall through mucosa, submucosa, muscularis, and serosa). |
| Macroscopic / Endoscopic Features | Diffuse mucosal erythema, loss of normal vascular pattern, friability, superficial ulceration, and inflammatory pseudopolyps. Longstanding disease yields a shortened, featureless "lead-pipe colon". | Deep longitudinal serpentine or "knife-cut" ulcers, aphthous ulcers, thickened bowel wall with "cobblestoning", luminal strictures, and fat wrapping (creeping fat). Barium studies show the "string sign of Kantor". |
| Histopathological Hallmarks | Crypt architectural distortion, crypt abscesses (neutrophilic aggregates in crypt lumens), goblet cell mucin depletion. No granulomas. | Non-caseating epithelioid granulomas (in ~50%), transmural lymphoid aggregates, fissuring ulcers, knife-cut fissures leading to sinuses. |
| Clinical Hallmarks | Recurrent bloody diarrhoea with mucous, severe tenesmus, faecal urgency, and crampy left-lower-quadrant abdominal pain. | Colicky right-lower-quadrant pain, chronic watery or non-bloody diarrhoea, weight loss, low-grade fever, malnutrition (malabsorption of vitamin B12 and bile salts in terminal ileum). |
| Perianal Complications | Absent. Perianal disease rules out uncomplicated UC. | Common in >30%: complex anal fistulae, perianal abscesses, deep fissures, and large oedematous skin tags. |
| Strictures & Fistulae | Extremely rare (stricture in UC must be assumed malignant until proven otherwise). | High frequency: entero-enteric, entero-vesical (pneumaturia/fecaluria), entero-cutaneous, and entero-vaginal fistulae; fibrous strictures causing bowel obstruction. |
| Smoking Association | Smoking is protective (cessation often precipitates disease onset or severe relapse). | Smoking is a major risk factor; accelerates progression, increases relapse rates, and doubles surgical requirement. |
| Serological Biomarkers | pANCA (perinuclear antineutrophil cytoplasmic antibodies) positive in ~60–70%. | ASCA (anti-Saccharomyces cerevisiae antibodies) positive in ~50–60%. |
3. Extraintestinal Manifestations of IBD
Extraintestinal manifestations affect up to 40% of patients with IBD and fall into two clinical categories:
Related to Disease Activity (Parallel Colonic Flares)
- Erythema Nodosum: Tender, erythematous, non-ulcerative subcutaneous nodules over the anterior tibial surfaces; resolves in tandem with treating bowel inflammation.
- Episcleritis: Painless or mildly aching injection of the superficial episcleral vessels; vascular engorgement blushes white with topical phenylephrine; tracks intestinal inflammation.
- Enteropathic Peripheral Arthritis: Non-deforming, migratory, asymmetric oligoarthritis affecting large joints (knees, ankles, wrists).
- Aphthous Oral Ulcers: Painful mucosal shallow ulcers occurring during active intestinal exacerbations.
Independent of Disease Activity (Unrelated to Bowel Flares)
- Pyoderma Gangrenosum: Commences as a small pustule that rapidly breaks down into a chronic, deep, agonizing ulcer with violaceous, undermined necrotic edges, classically on the shins. Key Clinical Pearl: Shows pathergy (exacerbated by trauma or surgical debridement). Treated systemically with high-dose corticosteroids or infliximab; surgical debridement is strictly contraindicated.
- Anterior Uveitis: Painful red eye accompanied by photophobia, blurred vision, and ciliary flush; emergency ophthalmic management with topical steroids and cycloplegics required to prevent blindness.
- Axial Spondyloarthropathy: Ankylosing spondylitis and sacroiliitis; strongly linked to HLA-B27; runs a progressive course unaffected by medical or surgical bowel treatment.
- Primary Sclerosing Cholangitis (PSC): Chronic fibrosing inflammation of the intra- and extrahepatic bile ducts, producing multifocal "beaded" strictures. Strongly associated with UC (~80% of PSC patients have UC). Confers an extraordinarily high lifetime risk of cholangiocarcinoma and accelerated colorectal dysplasia.
4. Acute Severe Ulcerative Colitis & Truelove-Witts Criteria
Acute severe ulcerative colitis (ASUC) is a medical emergency carrying significant mortality if unrecognized. Hospitalized patients are stratified using the Truelove and Witts criteria.
Truelove and Witts Diagnostic Definition of ASUC
To meet the criteria for Acute Severe Ulcerative Colitis, the patient must have:
- Stool Frequency: ≥ 6 bloody bowel movements per day, PLUS
- At least ONE systemic toxicity sign:
- Temperature: > 37.8 °C (oral)
- Pulse Rate: > 90 bpm
- Haemoglobin: < 105 g/L (anaemia)
- Erythrocyte Sedimentation Rate (ESR): > 30 mm/hour (or CRP > 45 mg/L)
Acute Emergency Management Protocol
- Immediate Inpatient Admission: Admit under joint gastroenterology and colorectal surgery care.
- Intravenous Corticosteroids: Commenced immediately: Intravenous Hydrocortisone 100 mg four times daily (QDS) (or methylprednisolone 60 mg/day).
- Venous Thromboembolism (VTE) Prophylaxis: Active inflammatory colitis induces an intense pro-thrombotic state. Administer prophylactic low-molecular-weight heparin (LMWH, e.g. enoxaparin) and apply graduated compression stockings. Rectal bleeding is not a contraindication to prophylactic anticoagulation in ASUC.
- Daily Abdominal Radiographs: Screen daily for toxic megacolon (transverse colon luminal diameter > 6 cm with mucosal thumbprinting and loss of haustra). Toxic megacolon carries imminent perforation risk.
- Contraindicated Medications: Antimotility agents (loperamide, codeine) and anticholinergic drugs are strictly contraindicated because reducing gut motility precipitates toxic megacolon.
- Flexible Sigmoidoscopy: Perform an unsedated, un-prepped bedside flexible sigmoidoscopy with mucosal biopsies to confirm severe active colitis and exclude cytomegalovirus (CMV) colitis. Full colonoscopy is contraindicated due to perforation risk.
Day 3 Travis (Oxford) Criteria & Medical Rescue
On Day 3 of IV hydrocortisone, patients must be formally evaluated using the Travis (Oxford) criteria:
- Stool frequency > 8 per day, OR
- Stool frequency > 3 per day PLUS CRP > 45 mg/L.
Important
Meeting the Travis criteria on Day 3 predicts an 85% likelihood of emergency colectomy during that admission. This mandates immediate escalation to medical rescue therapy:
- Infliximab: Monoclonal anti-TNF antibody (5 mg/kg IV infusion), provided latent tuberculosis and hepatitis B have been screened and ruled out; OR
- Ciclosporin: Calcineurin inhibitor (2 mg/kg/day continuous IV infusion, targeting trough level 150–250 ng/mL).
If the patient fails to respond within 5 to 7 days of rescue therapy, or exhibits worsening toxic megacolon, systemic peritonitis, or massive haemorrhage, emergency subtotal colectomy with end-ileostomy must be performed without delay.
5. Colorectal Carcinoma: Epidemiology & 2-Week-Wait Referral Pathways
Colorectal cancer (CRC) is the fourth most common cancer and second most common cause of cancer death in the United Kingdom. Over 95% are adenocarcinomas developing through the adenoma-to-carcinoma sequence (involving mutations in APC, KRAS, and TP53) or the microsatellite instability (MSI) pathway driven by DNA mismatch repair defects (as in Lynch syndrome).
NICE NG12 (2023 Update): FIT-Based Colorectal Cancer Referral
Since August 2023, NICE NG12 (incorporating diagnostics guidance DG56) uses the faecal immunochemical test (FIT) to triage most symptomatic patients in primary care.
Offer FIT to adults with any of:
- an abdominal mass
- a change in bowel habit
- iron-deficiency anaemia
- age 40 or over with unexplained weight loss and abdominal pain
- age under 50 with rectal bleeding and either unexplained abdominal pain or weight loss
- age 50 or over with unexplained rectal bleeding, abdominal pain or weight loss
- age 60 or over with anaemia, even without iron deficiency
Refer using the suspected cancer pathway if:
- the FIT result is 10 micrograms of haemoglobin per gram of faeces (µg Hb/g) or more, or
- there is a rectal mass, an unexplained anal mass or unexplained anal ulceration (refer directly; FIT not needed).
A FIT below 10 µg Hb/g makes colorectal cancer unlikely but does not exclude it: safety-net, and refer if clinical concern persists (or if a FIT kit is not returned). Iron-deficiency anaemia in men and postmenopausal women is also investigated with bidirectional endoscopy (gastroscopy and colonoscopy) under British Society of Gastroenterology (BSG) 2021 guidance, unless FIT triage or comorbidity changes the plan.
| Feature | NICE NG12 Action |
|---|---|
| FIT 10 µg Hb/g or more | Suspected cancer pathway referral (colonoscopy or CT colonography) |
| Rectal mass, unexplained anal mass or anal ulceration | Direct suspected cancer pathway referral |
| Abdominal mass, change in bowel habit, iron-deficiency anaemia or age-based symptoms above | Offer FIT first; refer if 10 µg Hb/g or more |
A 24-year-old woman with a 2-year history of ulcerative colitis presents to the emergency department with a 4-day exacerbation of severe bloody diarrhoea. She reports passing 9 watery, bloody stools per day accompanied by severe tenesmus. On examination, she appears toxic and flushed. Her temperature is 38.2°C, blood pressure is 102/64 mmHg, and heart rate is 108 bpm. Abdominal examination reveals moderate left-iliac-fossa tenderness without rebound or guarding. Laboratory results show: haemoglobin 94 g/L, white cell count 14.2 × 10⁹/L, and C-reactive protein (CRP) 78 mg/L. A plain abdominal radiograph demonstrates a transverse colon diameter of 4.2 cm without free gas. What is the most appropriate immediate medical management for this patient?
Admission, IV hydrocortisone 100 mg four times daily and prophylactic LMWH
Intravenous infliximab 5 mg/kg infusion as primary monotherapy
Emergency subtotal colectomy and end-ileostomy within 12 hours
Oral mesalazine 4 g daily and oral loperamide 4 mg PRN for symptom control
A 29-year-old man admitted with acute severe ulcerative colitis has completed 3 full days of intravenous hydrocortisone 100 mg QDS. On Day 3 reassessment, he continues to pass 9 bloody bowel motions over the preceding 24 hours. His temperature is 37.6°C, heart rate is 88 bpm, and his repeat CRP is 56 mg/L. A repeat plain abdominal radiograph reveals a transverse colon diameter of 4.8 cm with no evidence of perforation or free air. The colorectal surgical team has been consulted. According to the Travis (Oxford) criteria and BSG guidelines, what is the most appropriate next step in management?
Discharge the patient on high-dose oral prednisolone 60 mg daily with outpatient gastroenterology follow-up
Proceed immediately to emergency total proctocolectomy with permanent ileostomy within 2 hours
Continue intravenous hydrocortisone monotherapy for a further 7 days before modifying the treatment plan
Initiate medical rescue therapy with intravenous infliximab (or ciclosporin) alongside urgent surgical review
A 64-year-old man presents to his GP describing a 2-month history of fatigue and vague lower abdominal fullness. He notes that over the past 8 weeks, his bowels have opened 4 to 5 times daily with loose stools, whereas his lifelong baseline was a single formed bowel movement each morning. He has observed occasional dark streaks in the stool but denies severe pain or haematemesis. Blood tests demonstrate: haemoglobin 88 g/L (normal 130–175 g/L), mean corpuscular volume (MCV) 71 fL (normal 80–100 fL), and serum ferritin 8 mcg/L (normal 30–400 mcg/L). Renal and liver function tests are within normal parameters. A faecal immunochemical test (FIT) returns 112 µg Hb/g faeces. What is the most appropriate immediate diagnostic referral for this patient?
Perform a 13C-urea breath test to investigate for Helicobacter pylori gastritis
Routine outpatient referral to the gastroenterology clinic for evaluation of irritable bowel syndrome
Referral via the suspected colorectal cancer pathway for urgent colonoscopy
Prescribe oral ferrous sulfate 200 mg three times daily and repeat the full blood count in 3 months
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