Write a short note on lower gastrointestinal bleeding.

Definition

Lower gastrointestinal (GI) bleeding is bleeding originating distal to the ligament of Treitz. It usually presents as haematochezia (fresh or altered blood per rectum), though bleeding from the right colon or small bowel may present as melaena.

A crucial initial caveat: brisk UPPER GI bleeding can present as haematochezia with haemodynamic instability — and upper GI bleeding is both commoner and more lethal. In any patient with haematochezia and shock, exclude an upper GI source first.

Causes BY Age and Frequency

In Indian practice, add: intestinal tuberculosis, amoebic colitis, enteric fever with ileal ulceration, and hookworm infestation (as a cause of occult blood loss and iron deficiency).

Clinical Assessment

History:

• the colour and pattern of bleeding (bright red suggests a distal source; maroon suggests right colon or small bowel; melaena suggests an upper or proximal source), whether blood is mixed with stool (proximal) or coating it or seen on the paper (anorectal)
• associated pain (present in ischaemia and IBD, absent in diverticular and angiodysplastic bleeding)
• change in bowel habit
• weight loss
• fever and diarrhoea
• NSAID, anticoagulant and antiplatelet use
• previous radiotherapy, polypectomy or aortic surgery
• family history of malignancy or IBD.

Examination:

• haemodynamic assessment first — pulse, blood pressure, postural change, perfusion
• abdominal examination for tenderness and masses
• digital rectal examination with proctoscopy, which identifies anorectal causes and confirms the nature of the blood — a step frequently omitted.

Investigations

• CBC, coagulation profile, renal function, liver function, blood grouping and cross-match.
• A urea:creatinine ratio that is disproportionately raised suggests an UPPER GI source.
• Upper GI endoscopy — performed first in haemodynamically unstable patients with haematochezia, or where the urea is raised, to exclude a rapidly bleeding upper source.
• Colonoscopy — the primary investigation for lower GI bleeding: both diagnostic and therapeutic, ideally after bowel preparation within 24 hours in significant bleeding.
• CT angiography — for active, brisk bleeding; localises the site rapidly and guides embolisation. Requires an active bleeding rate above about 0.3–0.5 mL/min.
• Radionuclide (technetium-labelled red cell) scan — detects slower bleeding but localises poorly.
• Catheter angiography — for localisation with the option of therapeutic embolisation.
• Capsule endoscopy and enteroscopy — for obscure gastrointestinal bleeding, where upper and lower endoscopy are negative and the small bowel is the presumed source.
• Meckel's scan (technetium pertechnetate) in young patients.

Management

1. Resuscitation and risk assessment first

• Two large-bore cannulae, crystalloid, restrictive transfusion strategy, correction of coagulopathy, and monitoring. Most lower GI bleeding stops spontaneously (about 80%) — but the minority who continue to bleed require rapid, organised care.
• Reverse anticoagulation where the bleeding is major, balancing the thrombotic risk of doing so.
• Identify high-risk features: haemodynamic instability, ongoing bleeding, significant comorbidity, anticoagulant use, and a haemoglobin below 10 g/dL.

2. Definitive therapy — directed at the cause

• Colonoscopic haemostasis — clips, thermal coagulation, adrenaline injection, band ligation; endoscopic band ligation or infrared coagulation for haemorrhoids.
• Angiographic embolisation — for ongoing bleeding localised by CT angiography and not amenable to endoscopic treatment; effective, with a risk of bowel ischaemia.
• Surgery — for uncontrolled bleeding despite the above, or for the underlying pathology (segmental colectomy for a localised source; malignancy resection). Blind or "blind subtotal" colectomy is a last resort and carries high morbidity, which is why localisation before surgery is so important.
• Treat the underlying condition — IBD therapy, antimicrobials for infective colitis, antitubercular therapy, tumour resection, and management of radiation proctitis (argon plasma coagulation, sucralfate enemas).

3. Prevention of recurrence — review and minimise NSAIDs, aspirin and anticoagulants; iron replacement; colonoscopic surveillance where indicated; and treat haemorrhoids and constipation.