Key Facts

Lower GI bleeding (LGIB) is a common cause of emergency admission. While most cases are self-limiting and can be managed conservatively, massive LGIB requires prompt investigation and may need endoscopic, radiological, or surgical intervention.

Epidemiology

Incidence ~20-30 per 100,000 per year. Incidence increases with age (diverticular disease, angiodysplasia, malignancy). Accounts for ~20% of all GI bleeding. Overall mortality ~3-5% (lower than UGIB).

Aetiology

• Diverticular bleeding: ~30% — most common cause of massive LGIB; usually painless
• Haemorrhoids: ~20% — bright red blood on wiping/in pan; rarely massive
• Colorectal cancer: ~10% — altered bowel habit, iron deficiency, weight loss
• Angiodysplasia: ~10% — vascular malformations, usually right colon; associated with aortic stenosis (Heyde syndrome), CKD
• IBD: ~5% — bloody diarrhoea, mucus, systemic features
• Ischaemic colitis: elderly, CVD, splenic flexure pain, bloody diarrhoea
• Radiation proctitis: post-pelvic radiotherapy
• Others: Meckel's diverticulum (children/young adults), solitary rectal ulcer, NSAID colopathy

Pathophysiology

Diverticular bleeding: erosion of the vasa recta where they course over the dome of a diverticulum. Angiodysplasia: degenerative vascular ectasias from chronic low-grade venous obstruction (usually right colon in elderly). Ischaemic colitis: reduced colonic perfusion (watershed areas — splenic flexure, rectosigmoid junction) causing mucosal ischaemia and bleeding.

Minor LGIB

• Bright red blood on wiping or in toilet pan
• Mixed with/on surface of stool
• Usually haemorrhoids, fissure, or minor anorectal cause

Moderate LGIB

• Passage of larger volumes of fresh/maroon blood
• Haemodynamically stable
• Diverticular, angiodysplasia, cancer, IBD

Massive LGIB

• Significant haemorrhage with haemodynamic compromise
• Often diverticular or angiodysplasia
• Remember: massive UGIB can mimic LGIB (haematochezia from brisk upper source)

Red Flags

• Haemodynamic instability
• Continued active bleeding
• Age >60 with new-onset PR bleeding (malignancy until proven otherwise)
• Anticoagulated patient with bleeding
• Iron deficiency anaemia (chronic occult blood loss — malignancy)
• Weight loss + PR bleeding (malignancy)

Bedside

• A-E assessment: haemodynamic stability
• DRE + proctoscopy: anorectal cause assessment (haemorrhoids, mass, fissure)
• Oakland score: risk stratification (age, sex, Hb, previous LGIB admission, DRE findings, heart rate, systolic BP)

Bloods

• FBC: Hb (may take time to drop in acute bleed)
• U&Es: renal function
• Coagulation (INR): anticoagulant therapy
• Group and save/crossmatch: if significant bleeding
• Lactate: tissue perfusion

Imaging

• CT angiography: first-line for haemodynamically significant LGIB — detects active bleeding if >0.3-0.5 mL/min; localises source for potential embolisation or surgery
• CT abdomen/pelvis: if other pathology suspected (malignancy, ischaemic colitis)

Endoscopy

• Colonoscopy: after bowel preparation for stable LGIB — diagnostic (identify cause) + therapeutic (polypectomy, APC for angiodysplasia, clipping); usually within 24-48 hours
• Flexible sigmoidoscopy: quick assessment for left-sided pathology
• OGD: ALWAYS consider if no lower source found (massive UGIB presenting as haematochezia)

Special Tests

• Mesenteric angiography: if CT angiography shows active bleeding — can perform selective embolisation
• Tagged red cell scan (Tc-99m): detects slower bleeding (>0.1 mL/min); less widely used now
• Capsule endoscopy: for obscure/recurrent bleeding with negative OGD and colonoscopy
• FIT (faecal immunochemical test): for stable patients with PR bleeding to triage for colonoscopy (NICE DG30)

Non-pharmacological

• Resuscitation: as for all GI bleeding — A-E, IV access, crossmatch
• Restrictive transfusion: target Hb 70-80 g/L
• Correct anticoagulation: if on warfarin/DOACs, balance bleeding risk vs thrombotic risk

Pharmacological

• Tranexamic acid: NOT routinely recommended (HALT-IT trial)
• Stop/reverse anticoagulation: if clinically significant bleeding — vitamin K, PCC, idarucizumab as appropriate
• Treat underlying cause: iron replacement (if chronic), IBD therapy, H. pylori eradication (if also upper source)

Surgical/Interventional

• Endoscopic therapy: APC (argon plasma coagulation) for angiodysplasia and radiation proctitis, polypectomy, clipping
• Mesenteric embolisation: for active diverticular or angiodysplastic bleeding localised on CT angiography
• Surgery: emergency colectomy for uncontrolled massive LGIB (segmental if source localised; subtotal if not); rarely needed (<5% of admissions)
• Colonic stenting: not for bleeding but relevant if cancer causing obstruction

Referral Criteria

• Oakland score ≤8: consider outpatient investigation
• Oakland score >8: inpatient management
• Massive LGIB: emergency GI, surgical, and IR teams
• 2WW referral: age ≥50 with unexplained rectal bleeding (NICE NG12); FIT ≥10 in symptomatic patients
• All persistent/unexplained LGIB for colonoscopy

Overall LGIB mortality is ~3-5% (lower than UGIB). 80-85% of LGIB stops spontaneously. Diverticular bleeding: self-limiting in 80% but 25% recurrence rate. Angiodysplasia: recurrent bleeding common (up to 50%); APC therapy effective. Massive LGIB requiring emergency colectomy has ~10-20% mortality. Screen-detected colorectal cancer (FIT-positive) has significantly better outcomes than cancer presenting with bleeding.

Oakland Score for LGIB Risk Stratification

LGIB Management Algorithm