bleeding may occur from any part from the gut .blood loss may be chronic and occult bleeding resulting in anaemia .overt blood loss varies widely in presentation .excluding haemorrhoidal bleeding .the lower gastrointestinal tract is less commonly a source of overt major
 bleeding than the stomach or duodenum

Clinical examination

 Blood originating from the sigmoid colon or distally may be dark or usually bright red and copious ,that from more proximal sites in the colon or the distal small intestine is usually dark red or black ,although it does not have the sticky consistency or typical offensive smell of partially digested blood that characterizes the melaena of upper gastrointestinal bleeding . occasionally upper gastrointestinal bleeding may be brisk enough to cause the passage of unaltered blood per rectum thus mimicking a colonic bleed .there may be a history of previous episodes or patient may be known to suffer from piles or ulcerative colitis
clinical examination is usually unremarkable in term of localizing the source of bleeding
a digital rectal examination is essential as this provides the best clue to the origin of the bleed .tachycardia may be the only sign
though haemorrhagic shock may be present in extreme cases

  Causes of bleeding
Haemorrhoids or piles

These may bleed profusely . the blood is bright red and there is usually a history of blood passed per rectum after a motion . first degree piles are impalpable and present with bleeding only and thus a rectal examination may be entirely normal apart from blood staining of the glove . the bleeding will usually cease and the diagnosis can be established by proctoscopy at which time the haemorrhoids can be injected with 3%phenol


This an important cause of bleeding per rectum any cause of colitis may result in blood loss including ulcerative infective or ischaemic colitis, infective colitis with campylobacter species often presents with lower abdominal pain and the passage of frank blood per rectum . ulcerative colitis or Grohn,s colitis will result in diarrhea which may be blood stained . ischaemic coltits which is usually affects the splenic flexure may present with blood passed per rectum the blood tends to be dark and represents with sloughing of the nucosa resulting from the ischeamia rarely radiation enteritis may cause bleeding .if this is so then there will be a clear history of radiotherapy usually for a pelvic malignancy like cervical or prostatic carcinoma 

Diverticular diseases

 A diverticulum can bleed when it is not inflamed the perforating blood vessels penetrate adjacent to the neck of the diverticulum where they can easily be eroded by impacted faecoliths if there is inflammation bleeding does not result as mural oedema distance the vessels from the impacted faecoliths the bleeding may brisk and bright red and there are usually no symptoms or signs in the abdomen . diverticula at any site of the colon may bleed

The colonic mucosa may have small flat patches of telangiectatic vasculature rarely greater than one centimeter . these are termed angiodysplasia and they probably account for the majority of cases of acute and chronic colonic bleeds , diverticula at any site of the colon may bleed

Meckel,s diverticulum
A meckel,s diverticulum may be the site of ectopic gastric mucosa this will produce gastric acid and whilst the acid tolerating mucosa within the diverticulum will be relatively protected the adjacent ileal mucosa will be intolerant and a peptic ulcer may develop next to the neck of the diverticulum this ulcer may bleed like its counterparts in the duodenum and will present wit the passage of dark blood per rectum often copious


Carcinoma of the colon very rarely presents as massive bleeding but frequently causes anaemia from chronic occult blood loss . however the passage of dark blood per rectum may indicate a carcinoma . colonic polyps lymphomas lieomyomas
and haemangiomas of the small bowel or colon may bleed

 Bowel ischaemia

 Intestinal ischaemia including ischaemic colitis results in intraluminal blood and may present with dark blod passed per rectum causes include mesenteric arterial or venous infarction or mesentric embolism . ischaemia as a result of bowel strangulation or obstruction may result in blood loss as seen with intussusception acute hypovolaemic shock may cause sloughing of the intestinal mucosa resulting in blood passed per rectum


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