Rectal Bleeding

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Last updated: August 11, 2020
Revisions: 10

Last updated: August 11, 2020
Revisions: 10

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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 can 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 source in the rectum or colon, however large upper GI bleeds can also present with haematochezia*

Common causes of acute lower GI bleeding include diverticular disease, ischaemic or infective colitis, haemorrhoids, malignancy, angiodysplasia, Crohn’s disease or Ulcerative colitis, or radiation proctitis.

*A patient with a large fresh rectal bleed who is haemodynamically unstable should be considered to have an upper GI bleed until proven otherwise


Diverticulosis 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.

The incidence of diverticulosis increases with age. Diverticular disease bleeds are classically painless, whilst diverticulitis associated bleeds are often painful, secondary to the localised inflammation.


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.

The blood is classically on 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 a colorectal 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.

Clinical Features

Patients with PR bleeding should initially be stratified as either stable or unstable. Key aspects to ascertain from clinical assessment include:

  • Nature of bleeding, including duration, frequency, colour of the bleeding, relation to stool and defecation
  • Associated symptoms, including pain (especially association with defaecation), haematemesis, PR mucus, or previous episodes
  • Family history of bowel cancer or inflammatory bowel disease

Examine the abdomen for any localised tenderness or masses palpable. A PR examination is essential for every patient presenting with haemotochezia, allowing assessment for any rectal masses and ongoing presence of blood.

The Oakland Score

The Oakland Score can be used to help stratify patients presenting with a lower GI bleed to determine if outpatient management is feasible.

Factors used to determine the Oakland score are Age, Sex, Previous Admissions for Lower GI bleeding, PR findings, Heart Rate, Systolic Blood Pressure, and Haemoglobin Concentration.

All haemodynamically unstable bleeds should be approached in an A to E manner, and have a different approach than to stable bleeds.


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

In patients who are haemodynamically unstable, patients should be initially stabilised before undergoing an urgent CT angiogram (before any endoscopic therapy). This can identify the source of bleeding, as well as permitting potential therapeutic intervention with embolisation.

*Acute bleeds may not initially show reduced Hb level due to haemoconcentration, however ongoing bleeding will show a reduced Hb; the presence of an elevated serum urea to creatinine ratio suggests an upper GI source of bleeding being more likely

Further Investigations

Patients with stable bleeds will require a flexible sigmoidoscopy* (or colonoscopy) for further assessment, importantly to exclude left-colonic pathology (especially malignancy) and can often be performed as an outpatient.

In stable patients with PR bleeding and no abnormality identified on colonoscopy, upper GI endoscopy (OGD) should be performed to look for further sources of bleeding. If this proves inconclusive, further investigations such as capsule endoscopy or MRI small bowel scans may be required.

*If flexible sigmoidoscopy proves inconclusive, the patient should undergo a full colonoscopy.

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

Risk factors for adverse outcomes from any acute rectal bleeding include haemodynamic instability, ongoing haematochezia, age >60yrs , serum creatinine >150µmol/L, or significant co-morbidities.


95% of cases will settle spontaneously. Often young haemodynamically stable patients, in who the bleeding has stopped and have a low risk score, can be discharged and investigated as an outpatient.

Any unstable rectal bleed warrants urgent resuscitation, with a standard A to E approach, using IV fluid and blood products as required until stabilised

Any Hb <70 should trigger transfusion of packed red blood cells (unless the patient has a history of cardiovascular disease, then Hb <80 should be used). Patients on anti-coagulation should have this reversed urgently, with guidance from a haematologist as required.

Potential management options include:

  • Endoscopic haemostasis methods include injection (typically diluted adrenaline), contact and non-contact thermal devices (such as bipolar electrocoagulation or argon plasma coagulation), and mechanical therapies (endoscopic clips and band ligation)
  • Arterial embolisation is possible in those with an identified bleeding point (termed a “blush”) of sufficient size on angiogram

Surgical Intervention

Surgical intervention is rarely required, however may be considered in patients with ongoing lower GI bleeding with instability (or requiring continued transfusion), where endoscopic and radiographic treatment has failed.

Key Points

  • Any patient with rectal bleeding required a flexible sigmoidoscopy or colonoscopy
  • A patient with a large fresh rectal bleed who is haemodynamically unstable has an upper GI bleed until proven otherwise
  • Acute bleeds may not initially show an anaemia in the full blood count
  • Patients who are haemodynamically unstable need an emergency OGD and colonoscopy