Haematochezia

Diverticulosis

A colonic diverticulum is a herniation of the mucosa and submucosa through the muscle layer of the bowel at areas of weakness. It tends to occur alongside the teniae coli, at the entry points of the vasa recta and nerves. Diverticulosis , a term for the presence of multiple diverticula, most commonly involves the descending and sigmoid colon. Right-sided diverticulosis is common in the Asian population.

The risk of bleeding in patients with diverticulosis can be as high as 48% and is thought to be caused by the acute rupture of diseased vasa recta. Atherosclerotic disease is an independently risk factor for bleeding, which could explain why the increasing prevalence of this complication with age. Hypertension, smoking, steroid and the use of non-steroidal anti-inflammatory drugs (NSAIDs) are also risk factors.

The presentation is usually an acute painless haematochezia, with spontaneous resolution in 70% to 80% of patients. Of these, 25% to 30% will have recurrence of bleeding.

Angiodysplasia

Angiodysplasia is an acquired ectasia of veno-capillary channels in the mucosal and submucosal layers of the GI tract; it is most commonly found in the proximal colon and accounts for up to 3% to 30% of cases of LGIB. Angiodysplastic lesions increase with age and are the second most common cause of bleeding above the age of 65. The bleeding pattern can be acute massive, intermittent or occult. The main contrast to diverticular bleeding is the high rate of self-limiting re-bleeding in patients (80%) with untreated lesions. A small proportion of cases are contributed by angiodysplasia in the small bowel.

Other rarer vascular anomalies—including arteriovenous malformation, haemangioma and telangiectasias—tend to occur in younger patients.

Enterocolitis

Enterocolitis is a collective term for a vast array of pathophysiology involving the inflammation of the small bowel and colon.

By far the most common form of enterocolitis is infectious in origin. In this group, fever, abdominal pain, tenesmus, vomiting and diarrhoea dominate the clinical picture. Haematochezia is often reported as part of the diarrhoea episode rather than frank bleeding. When present, bleeding usually points a bacterial or parasitic cause, although this can be seen in severe forms of haemorrhagic virus infection such as dengue and Ebola. Enterohaemorrhagic Escherichia coli , Shiga toxin–producing E. coli , Shigella, Salmonella and Campylobacter jejuni are well-known agents producing bloody diarrhoea. The term dysentery usually refers to Shigella -related diarrheal disease. Ascariasis, necatoriasis, taeniasis and amoebiasis are parasitic causes of chronic intermittent haematochezia, often associated with abdominal pain, loss of appetite and anaemia

Ischaemic colitis is the result of a reduction in mesenteric blood flow causing ischaemia of a segment of colon. This typically occurs in watershed areas, such as the splenic flexure and the rectosigmoid junction. Patients are usually elderly with risk factors for vascular disease such as atherosclerosis, hypertension, diabetes, cardiac arrhythmias and thrombophilia. Chronic constipation and irritable bowel syndrome are independent risk factors. Possible aetiologies in younger patients include vasculitis, drugs (cocaine, methamphetamines), sickle cell anaemia and endurance running. The common presentation is acute abdominal pain followed by haematochezia within 24 hours. There may be paucity of clinical signs, especially in the elderly and immunocompromised, unless bowel infarction and peritonism has occurred.

Radiotherapy or radiation exposure also causes ischaemic enterocolitis. The result is inflammation, sloughing of mucosa and bleeding. Haemorrhagic radiation proctitis is a potential complication of prostate brachytherapy, affecting 4% to 13% of patients.

Inflammatory bowel disease (see Chapter 7.11 )

Small to moderate amounts of rectal bleeding occur in up to 50% of patients with ulcerative colitis, often accompanied by other features such as loss of appetite and prolonged diarrhoea. In contrast, haematochezia and diarrhoea are less prominent in Crohn disease.

Neoplasia

Neoplasms of the bowel present as painless occult bleeding but may result in mild recurrent bleeding due to erosion or ulceration of mucosa. They have associated symptoms of weight loss, altered bowel habit, abdominal pain or intestinal obstruction. Colon cancer is the predominant cause of rectal bleeding from neoplastic disease and is more common in patients above 50 years of age. From population studies, the diagnosis of lower GI bleeding is also a predictor of increased risk for non-colorectal GI cancer beyond 1 year of follow-up.

Post-polypectomy bleeding may result in significant blood loss, which is often arterial in nature. This can occur between hours to weeks after polyp removal.

Anorectal disorders (see Chapter 7.14 )

Haemorrhoids are the most common cause of haematochezia. Most episodes are self-limiting and respond well to conservative treatment. Rectal varices are porto-systemic anastomoses that develop in almost every patient with portal hypertension, but bleeding from these is rare.

Other causes of haematochezia from anorectal conditions include fissures, fistulae, abscesses, ulcers, foreign-body and rectal trauma. This is usually self-limiting and the treatment is targeted at the primary condition and symptomatic relief.

Clinicians should keep in mind that the detection of anorectal disease on examination does not exclude the possibility of a more proximal source of bleeding.

Aortoenteric fistula

This complication occurs as a rare sequela of endovascular abdominal aortic aneurysm repair (secondary aortoenteric fistulae) and is probably due to inflammation and prosthetic leak. The site of the fistula is most often the duodenum. The traditional triad of abdominal pain, sepsis and GI bleeding is seen in only 30% of patients. There may be a ‘herald bleed’ prior to catastrophic exsanguinating haemorrhage. A primary aortoenteric fistula, where an untreated aneurysm exerts pressure and erodes into the GI tract, is even rarer.