Rectal Bleeding

Rectal bleeding (or haematochezia) is the passage of fresh blood per rectum. It is generally caused by bleeding from the lower gastrointestinal tract, but may occur in patients with large upper GI bleeds or from small bowel lesions.

The causes of rectal bleeding range from benign to life-threatening disease, and as with all types of bleeding, haematochezia can eventually result in significant haemodynamic instability if not managed appropriately.

In this article, we shall look at the causes, key clinical features, investigations and management of haematochezia.

Figure 1 – The blood supply of the large bowel

Differential Diagnosis

Fresh rectal bleeding most commonly results from a lesion in the rectum or colon. The most common causes for haematochezia are diverticular disease, angiodysplasia, haemorrhoids, and malignancy.

However, brisk fresh rectal bleeding may well be from an actively bleeding stomach ulcer. Indeed, a patient with a large fresh rectal bleed who is haemodynamically unstable has an upper GI bleed until proven otherwise.

Diverticular Disease

Diverticular disease is the most common cause of lower gastrointestinal bleeding. Diverticula are outpouchings of the bowel wall that are composed only of mucosa, most commonly in the descending and sigmoid colon.  Their incidence increases with age.  Diverticular bleeds are classically painless and are indistinguishable clinically from angiodysplasia, which are small arterio-venous malformations in the colonic wall.


Figure 2  – Haemorrhoids located in the 3, 7, and 11 o’clock positions

Haemorrhoids are pathologically engorged vascular cushions in the anal canal that can present as a mass, with pruritus, or fresh red rectal bleeding.

This is classically on the paper or the surface of the stool or toilet pan, rather than mixed in with it. Large haemorrhoids can also thrombose which can be extremely painful.


With any case of PR bleeding, especially in the elderly population, malignancy should be suspected, as this may be from a colo-rectal cancer.

In the assessment of any patient with haematochezia, it is important to enquire about other lower GI symptoms, weight loss, or relevant family history, potentially suggestive a diagnosis of malignancy.

Any patient with rectal bleeding in the absence of local anal symptoms (such as pruritus) must have cancer excluded by a flexible sigmoidoscopy or colonoscopy

Other Causes

Other less common causes of fresh rectal bleeding include anal fissures, inflammatory bowel disease, ischaemic colitis and aorto-enteric fistula.

Clinical Features

Key aspects to ascertain from clinical assessment includes

  • Nature of bleeding – duration, frequency, colour of the bleeding, relation to stool and defecation
  • Associated symptoms – including pain (whether it wakes them at night, is relieved or worsened by defaecation), haematemesis, mucus, previous episodes
  • Family history of bowel cancer or inflammatory bowel disease

A PR examination is essential for every patient presenting with haemotochezia, allowing assessment for any rectal masses or anal fissures


All patients presenting with rectal bleeing should have routine bloods* (FBC, U&Es, LFT, coagulation studies) and a Group and Save requested (as a minimum). Stool cultures are also useful to exclude infective causes.

*Acute bleeds may not initially show reduced Hb level due to haemoconcentration, however ongoing bleeding will show a reduced Hb 

Patients who are haemodynamically stable require a flexible sigmoidoscopy for further assessment, importantly to exclude left-colonic malignancy and to assess for further underlying pathology, and can often be performed as an outpatient.

If flexible sigmoidoscopy proves inconclusive, patients made undergo a full colonoscopy (if symptoms suggest more proximal disease) or an angiogram. Angiography is the most used imaging modality to further evaluate such cases, allowing for the identification of culprit bleeding vessels and also permits for therapeutic intervention if deemed possible, typically via arterial embolisation.

In patients who are haemodynamically unstable, an emergency OGD +/- CT angiogram with embolization will be warranted, alongside suitable resuscitation.

Figure 3 – Endoscopic image of angiodysplasia being treated with argon plasma coagulation


Any acute large rectal bleed warrants careful resuscitation, with a standard ABCDE approach, gaining 2 large bore cannulae, IV fluid, and blood products (if required).

95% of cases will settle spontaneously. Patients who are stable and are otherwise fit, in whom the bleeding has stopped and who have a normal Hb, can often be discharged, to be investigated as an outpatient; older patients usually need admission for observation.

A minority of patients become unstable or have ongoing bleeding.  These patients need resuscitation and urgent endoscopy and CT angiogram.  A small number of patients need a laparotomy but “blind” surgery has a high mortality and should generally be avoided.

Key Points

  • A patient with a large fresh rectal bleed who is haemodynamically unstable has an upper GI bleed until proven otherwise
  • Any patient with rectal bleeding in the absence of local anal symptoms (such as pruritus) must have cancer excluded by a flexible sigmoidoscopy or colonoscopy
  • Acute bleeds may not initially show an anaemia in the full blood count due to haemoconcentration; ongoing bleeding will show a reduced Hb
  • Patients who are haemodynamically unstable need an emergency OGD +/- CT angiogram with embolisation


Question 1 / 4
What is the blood supply to the ileum?


Question 2 / 4
If colonoscopy is negative, what is the next line of investigation in those presenting with significant haematochezia


Question 3 / 4
Which value in the clotting screen is most affected by warfarin?


Question 4 / 4
A 34 year old male presents with a 1 day history of bright red blood per rectum. He denies any abdominal pain or nausea or vomiting. He reports, however, several weeks of painful bowel movements and occasional blood on tissue paper when wiping. He has a long history of chronic constipation. On digital rectal exam, fresh blood is noted on the examiner’s glove, nil else. What is the most likely cause of this patient’s bleeding?


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