Lower GI bleeding is defined as bleeding distal to the ligament of Treitz (i.e. some of the small bowel, the colon and the rectum) which presents with the passage of bright red blood per rectum (haemotochezia) without the presence of blood in gastric aspirate.

Acute lower GI haemorrhage accounts for approximately 20% of all cases of GI haemorrhage and is a frequent cause of hospital admission.

Massive Haemorrhage implied if: large volumes of blood passed, 2+ units of RCC required or Haemodynamic instability.

Causes: –

1. Diverticular disease is the commonest cause of acute lower GI haemorrhage in the elderly. It is uncommon in those under the age of 40 years
2. Ischaemic colitis is the most common form of intestinal ischaemia and in most cases is transient & reversible. This diagnosis should be considered in patients presenting with abdominal pain and bloody diarrhoea.
3. Older adults are most likely to experience ischemia-related colitis because of underlying risk factors such as relative hypotension, heart failure, and arrhythmias
4. Infective colitis: A simple stool culture could reveal infective causes such as Salmonella, Shigella & Campylobacter. Stool culture may reveal the specific pathogen especially in traveller and systemically unwell patient or work as a food handler
5. Neoplasia (both carcinoma & polyps) can produce acute lower GI haemorrhage, although this more commonly presents with occult blood loss. Colorectal cancer is common in the UK and a frequent cause of cancer deaths. A digital rectal examination can save lives by identifying a rectal carcinoma.
6. Angiodysplasia is an acquired malformation of intestinal blood vessels with ectatic vessels in the mucosa and submucosa. It most commonly presents with iron deficiency anaemia and occult blood loss (bleeding is typically brisk, painless and intermittent).
7. Anorectal disease: –
   • Anal fissures can present with small amounts of fresh PR bleeding (often seen on toilet paper after wiping). They can be associated with severe pain which is worse on defecation.
   • Haemorrhoids are the most common cause of rectal bleeding in those under 50 years of age. It can be complicated with Haemorrhage, Prolapse or Thrombosis.
8. Massive upper GI bleeding can present with lower GI bleeding
9. Other causes of lower GI bleeding include:‎ Radiation injury, Meckels diverticulum, Other small bowel pathology (Solitary rectal ulcers, Portal colopathy, Prostate biopsy sites, Dieulafoy lesions, Endometriosis and Colonic varices).

Assessment of Severity:

Despite the fact that there is no well validated risk classification system, any patient with haemodynamic instability is at high risk for severe bleeding.

 Risk factors of poor prognosis mentioned include: being elderly, those with co-morbidities, on aspirin & those presenting with low BP/HR.

Clinical assessment: –

• Initial observations (such as dyspnoea, tachypnoea, tachycardia and, in particular, postural drop in blood pressure) are important and may indicate more significant blood loss and shock.
• The presence of abdominal tenderness on examination may help to suggest that the source of bleeding is more likely to be secondary to an inflammatory disorder, such as ischaemic colitis.
• A PR examination must be performed in all those suspected of GI haemorrhage (not only to assess the stool colour, presence of blood and so on, but also to look for anorectal lesions).
• Melaena (dark tarry stool) generally indicates an upper GI or small bowel source, whereas fresh, red blood generally indicates bleeding from the left colon or rectum. However, it is important to remember that this is not always the case.

Management algorithm: – As per the British Society of Gastroenterology

Management: –

• Prompt resuscitation and early involvement of surgical team are vital.
• Consider if major haemorrhage protocol needs to be activated if hemodynamically unstable and visibly excessive blood loss PR.
• Restrictive RBC thresholds (Hb trigger 70 g/L and a Hb concentration target of 70 – 90 g/L after transfusion) should be used, unless the patient has a history of cardiovascular disease, in which case a trigger of 80 g/L and a target of 100 g/L should be used.
• Colonoscopy is the investigation of choice in most patients with lower GI bleeds.
• CT angiography provides the fastest and least invasive means to localise the site of blood loss before planning endoscopic or radiological therapy. Angiography is performed in patients who is: –
  • Haemodynamically unstable or has a shock index (heart rate/systolic BP) of >1 after initial resuscitation
  • Having persistent GI bleeding with negative colonoscopy
  • in whom endoscopy is not feasible.
• Lower GI bleeding and anticoagulants: –
  • In cases of unstable gastrointestinal haemorrhage, warfarin should be reversed with prothrombin complex concentrate and vitamin K. For patients with low thrombotic risk, warfarin should be restarted at 7 days after haemorrhage.
  • In patients with high thrombotic risk (i.e., prosthetic metal heart valve in mitral position, atrial fibrillation with prosthetic heart valve or mitral stenosis, < 3 months after venous thromboembolism), guidelines recommend that low molecular weight heparin treatment be considered at 48hours after haemorrhage
  • consider treatment with inhibitors such as idarucizumab or andexanet for life-threatening haemorrhage on direct oral anticoagulants after discussion with haematology.
  •  Low dose aspirin is usually continued and NSAIDS stopped
• As LGIB associated with haemodynamic instability may be indicative of an UGIB source, British guidelines recommend that an upper endoscopy should be performed immediately if no source is identified by initial CTA. If the patient stabilises after initial resuscitation, gastroscopy may be the first investigation
• Surgical intervention is required when haemodynamic instability persists despite aggressive resuscitation or bleeding continues/recurs

Treatment of Anal fissure: –

• Conservative treatment à a high-fibre diet, adequate fluid intake, sitz baths, and topical analgesia.
• Stool softeners can be useful to make defecation less uncomfortable. 
• Topical GTN for 6 weeks.
• A proportion of patients find the headaches caused by glyceryl trinitrate intolerable and these patients may benefit from using topical diltiazem.
• Botulinum toxin is used after failure of topical treatment
• Surgical sphincterotomy à if symptoms persist & the patient is unresponsive to initial therapies

Treatment of haemorrhoid: –

• If the patient presents with mild intermittent bleeding, diet and lifestyle modifications to prevent constipation. Topical corticosteroids may soothe pruritic symptoms.
• Rubber band ligation is the treatment of choice for grade 2 haemorrhoids that are unresponsive to conservative management.
• Surgical haemorrhoidectomy is the most effective 1^st line approach for grade 4 internal haemorrhoids.