Introduction
Lower gastrointestinal (GI) bleeding is bleeding that arises distal to the ligament of Treitz, from the jejunum, ileum, colon or rectum. This topic covers the common sources, how they present, the diagnostic sequence from resuscitation to localisation, and the principles of endoscopic, radiological and surgical treatment. Upper GI bleeding and general bleeding physiology are dealt with in neighbouring topics.
Sources of bleeding
In adults the most frequent source of significant lower GI bleeding is the colon, and in older patients colonic diverticulosis is the leading cause. Bleeding from the upper GI tract can also present as maroon or bright red blood per rectum if it is brisk, so the source must never be assumed from the colour of the stool alone.
Clinical features
The presentation depends on the rate of bleeding and the site. Two main patterns are recognised:
- Haematochezia: passage of fresh or maroon blood per rectum, usually from the left colon, rectum or a brisk right-sided source
- Melaena: black, tarry, sticky stool, typically from a proximal source or a slow right colon bleed; it needs about 50 to 100 mL of blood in the gut to appear
- Occult bleeding: positive faecal occult blood test with iron deficiency anaemia, weakness and pallor
Assess the haemodynamic state early: tachycardia, hypotension, postural drop in blood pressure, pallor, cold peripheries, reduced urine output and altered consciousness indicate significant blood loss or shock. Ask about anticoagulant and antiplatelet therapy, NSAID use, previous GI bleeding, abdominal pain, change in bowel habit, weight loss, family history of colorectal cancer, and previous abdominal or pelvic surgery or radiotherapy.