Rectal bleeding

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Chronic rectal bleeding

Rectal bleeding is alarming although most causes are benign. Bleeding may be overt when noticed by the patient or occult when invisible blood loss is detectable by faecal occult blood test only. Management of rectal bleeding involves exclusion of a colorectal neoplasm and finding the cause of the bleeding.

Classification and causes of chronic rectal bleeding are given in Table 61, “Classification and causes of chronic rectal bleeding”.

Table 61. Classification and causes of chronic rectal bleeding
Classification Causes
Anal outlet bleeding Haemorrhoids
Bright blood per rectum, separate from the stool and often present as a smear of bright blood on the toilet paper Anal fissure
Anorectal cancer
Bleeding associated with defecation Rectal prolapse
No change in bowel habits Proctitis
No past or family history of colorectal neoplasm Colorectal neoplasm
Suspicious bleeding Diverticular disease
Dark blood or blood mixed with stool Inflammatory bowel disease
Change in bowel habit or passage of mucus Angiodysplasia
Past or family history of colorectal neoplasm


A detailed history should be taken. The nature of the rectal bleeding must be determined (duration, colour and amount of blood). Macroscopic bleeding recognised by the patient usually arises from the left side of the colon or rectum. Right-sided colonic bleeding usually presents with anaemia but without overt bleeding. The presence of anal pain should be inquired about. This occurs with anal fissure, strangulated haemorrhoids and anorectal cancer. Prolapse occurs with second- and third-degree haemorrhoids and with mucosal or full-thickness rectal prolapse. Other symptoms that may be seen are mixture of blood with stool, alteration in bowel habit, abdominal pain or distension and weight loss. These suggest that the source of bleeding is more proximally located in the colon or rectum. Anaemia is also indicative of a colonic or upper rectal lesion.

A past and family history of colorectal neoplasm must be gained from the patient, as well as a past history of colonic diseases such as inflammatory bowel disease.

Anorectal examination

Anorectal examination is essential in any patient presenting with rectal bleeding. Inspection should determine the presence of anal fissure, strangulated haemorrhoids or anal canal cancer. During straining, look for prolapsing haemorrhoids or rectal prolapse. Digital examination is used to feel for a rectal polyp or cancer.

This may not be possible in the presence of an acute anal fissure because of anal sphincter spasm and pain. Proctoscopy can be used to visualise any anal canal lesion and haemorrhoids. On rigid sigmoidoscopy the level of the rectum visualised should be recorded together with the level of any abnormality seen. Any suspicious lesion seen should be biopsied. The presence of blood clots or blood-stained faeces beyond the reach of the sigmoidoscope indicate a more proximal pathological process. Fibre-optic flexible sigmoidoscopy allows for an easier examination of the rectum and a variable length of the sigmoid and descending colon. In many specialist colorectal practices, this has replaced rigid sigmoidoscopy.

Special investigations

These include colonoscopy and air-contrast barium enema. Either of these tests may be performed to evaluate the colon. They are necessary only if the source of the bleeding is not clearly established and if there is doubt that a more proximal cause in the colon may be present. Colonoscopy has the advantage that small tumours and lesions that are bleeding may be more readily detected than by an air-contrast barium enema; as well as being therapeutic in that polyps may be removed endoscopically and angio-dysplasia may be treated with argon plasma coagulation or cautery. Capsule endoscopy is a newer investigation to identify a bleeding source in the small bowel.

Massive rectal bleeding

Clinical evaluation

A detailed history is important. The nature and amount of bleeding give an indication of the cause of the bleeding (Causes of massive rectal bleeding). Massive colonic haemorrhage is dark red or plum coloured and is to be differentiated from melaena, which is black. Melaena almost invariably arises from the stomach or small bowel. A rapidly bleeding peptic ulcer may occasionally present with bright red rectal bleeding. The haemodynamic condition of the patient will also reflect the severity of bleeding. Massive bleeding indicates bleeding of more than 1500 mL in 24 hours. In these circumstances, the patient has signs of shock on admission that demand urgent management with transfusion. Massive rectal bleeding will cease spontaneously in 80% of cases.

A prior history of a bowel disorder such as inflammatory bowel disease or haemorrhoids is ascertained. Use of anticoagulant therapy or non-steroidal anti-inflammatory drugs may contribute to bleeding. Liver disorders with impaired coagulation are also noted. A rectal examination with rigid proctosigmoidoscopy is performed to exclude bleeding haemorrhoids or rectal tumours.


Resuscitation should be immediately initiated with massive rectal bleeding while diagnostic tests are performed.


Upper gastrointestinal endoscopy

In cases of severe rectal bleeding with shock, an upper gastrointestinal endoscopy should be performed as soon as clinically feasible to exclude an upper gastrointestinal lesion, such as a bleeding peptic ulcer, oesophageal varices or aorto-enteric fistula. Alternatively a nasogastric tube is passed to exclude blood in the stomach.


Colonoscopy is performed as soon as feasible the following day with a full bowel preparation to locate the site of colonic bleeding, even if the bleeding continues. Emergency colonoscopy is difficult with active bleeding and requires a great deal of experience.


If the bleeding has ceased and the source of bleeding is yet to be identified, an enteroclysis is performed to exclude a gross small bowel lesion.

Capsule endoscopy

This involves patient swallowing a small videocapsule (Pillcam) which will capture digitised images of the small bowel. The duration of test is limited by the battery life of the videocapsule, which is eight hours. This is best done in a patient who is haemodynamically stable and has had recurrent gastrointestinal bleeding of unknown origin despite being previously investigated with upper gastrointestinal endoscopy, colonoscopy and barium small bowel followthrough.

Radionuclide scan

If bleeding continues and the site of haemorrhage is not located by colonoscopy, a radionuclide scan is done using technetium-99m sulphur colloid or technetium- 99m-labelled autologous red cells. A bleeding rate of 0.1–0.5 mL/min can be detected. The accuracy of these scans is variable, ranging from 40% to 90%. If the scan is positive and bleeding continues, mesenteric angiogram is performed to confirm the bleeding site.

Mesenteric angiogram

Selective angiogram of the inferior mesenteric, superior mesenteric and coeliac arteries is performed if bleeding continues and the rate is greater than 0.5 mL/min. Angiography is likely to be positive if there is active bleeding at the time of injection of contrast. If the site of bleeding is identified and the patient is elderly and frail, haemostasis with intra-arterial infusion of vasopressin through selective arterial cannulation should be considered. If effective, this is continued for 24 hours.


If bleeding continues, laparotomy is performed. If the site of bleeding is not clearly localised pre- or intra-operatively, intra-operative enteroscopy using a colonoscope inserted transorally is performed. The most distal part of the ileum may be examined using a colonoscope passed transanally. The bowel is trans-illuminated during intra-operative enteroscopy in a darkened room to detect angiodysplasias or small bowel angiomas. If the site of bleeding remains unclear, a subtotal abdominal colectomy is performed.


If the diagnosis is unresolved despite a full investigation, the patient is observed. If bleeding recurs, a full investigation is repeated as in a new case of active bleeding. Laparotomy and intra-operative enteroscopy may be necessary if these re-bleeding episodes are moderately severe.
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