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Diseases Causing Rectal Bleeding

See Anal Fissure.
Most common in young and middle-aged persons whose anal sphincter tonus is high.
Symptoms: pain/smarting on defecation or after defecation.
Bright blood is occasionally seen on the toilet paper after cleansing.
The fissure is usually situated dorsally on the skin of the anal canal. Aberrant location (non-midline) of the fissure, multiple almost asymptomatic fissures, and a macerated anus may suggest Crohn's disease. Other causes of fissure include anal neoplasm, leukaemia, lymphoma, sexually transmitted disease and tuberculosis.

If a young person has findings that are consistent with the symptoms, careful and gentle external examination of the anus, spreading the buttocks is often a sufficient investigation.
For treatment: see Anal Fissure.

See Haemorrhoids.
Haemorrhoids are defined as cushions on the anal sphincters that contain blood vessels and connective tissue. They are a normal structure of the anal canal.
Strain causes congestion that dilates the haemorrhoids, resulting over time in prolapse outside the anal canal.
A congested haemorrhoid may bleed during defecation if there is a mucosal tear. The bleeding is associated with strain on defecation, and the blood is bright red, dripping or jetting, and it discolours the toilet water. Prolapsed (grade III-IV) haemorrhoids may bleed from friction even at other times.
Other symptoms associated with haemorrhoids include perianal irritation and itch resulting from mucous leakage related to prolapse. Only incarcerated or thrombosed haemorrhoids cause pain. Haemorrhoids may also cause soiling because of incomplete closing of the anal canal due to tissue oedema.

See Diverticulitis and Diverticulosis.
Bleeding from diverticula is one of the most common causes of rectal haemorrhage in elderly patients. The diagnosis is based on the exclusion of other causes of bleeding. The site of bleeding is only rarely seen.
The bleeding originates from an artery at the fringe of the diverticulum or is caused by an arterio-venous malformation. It can be profuse, cause bloody diarrhoea and sometimes lead to shock.

Angiodysplasias are submucosal AV malformations occurring predominantly in the aged. Their origin is unknown.
The bleeding is venous and may be profuse or slow and may cause anaemia and require transfusions or surgery.

Correct hypovolaemia.
Localize the bleeding.
Correct coagulopathy.
With these therapies alone bleeding will stop in about 80-90% of patients.
Further non-surgical therapies include intravenous or arterial pitressin, embolization, endoscopic coagulation and finally surgical resection.

In inflammatory bowel diseases Ulcerative Colitis Crohn's Disease the bleeding and/or diarrhoea are usually associated with exacerbations of the disease. An earlier diagnosed disease or earlier intestinal bowel symptoms are the most important clues from the history.
Faecal calprotectin is the basic investigation.
The diagnosis is in most cases established by colonoscopy.
Fulminant colitis not responding to optimal treatment should be treated surgically.

See Colorectal Cancer Screening and Prevention of Colorectal Cancer Colonoscopy and Sigmoidoscopy.
Risk factors include e.g. age over 50 and family history.
Alarming symptoms and findings include involuntary weight reduction, unusual abdominal pain, changes in bowel function, abnormal abdominal status findings, anaemia.
Colonoscopy is the investigation of choice when a colorectal tumour is suspected.

Ischaemic colitis is a poorly characterized disease that is a cause of bloody diarrhoea in the elderly.
The elderly patient typically often has a history of a cardiovascular disease.
The attack starts with abdominal pain followed by bloody diarrhoea. Bloody diarrhoea, and palpable tenderness in the region of the affected part of the bowel are observed. The bleeding is rarely so heavy that it requires a transfusion. The risk of ischaemic colitis is highest in the first few postoperative days after the repair of an abdominal aortic aneurysm.
Can be diagnosed with colonoscopy. The differential diagnosis should include pseudomembranous colitis and infectious enteritides, especially in younger patients.

Vital functions ensured, rehydration
Localization
Optimize mesenteric blood flow - this often means cessation of digitalis and other medications that might cause mesenteric spasm.
Endoscopy is the most important diagnostic method.
CT angiography can be used to localize acute profuse bleeding. When the bleeding site has been localized it can be staunched through angiography.
Close monitoring for signs of transmural ischaemia or necrosis, which require emergency surgery
Capsule endoscopy can be used when searching for the cause of bleeding in the small intestine.

Strate LL, Gralnek IM. ACG Clinical Guideline: Management of Patients With Acute Lower Gastrointestinal Bleeding. Am J Gastroenterol 2016;111(4):459-74 [PubMed]