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Bleeding per rectum


What is the difference between "Anal" bleeding and "Bleeding per rectum"?

Bleeding coming from the anal canal is often lumped with bleeding coming from the rectum or higher up in the colon as bleeding per rectum. The distinction is however important as anal canal bleeding can be diagnosed effectively in the GP surgery setting and only need referral to a specialist if the cause does not respond to conservative outpatient measures or if the GP discovers a problem requiring surgery.

The distinction has practical implications. Anal bleeding needs a digital rectal examination & proctoscopy only. A rigid sigmoidoscopy is a bonus, but these patients do not require (in the absence of other bowel symptoms) flexible sigmoidoscopy, colonoscopy or a barium enema. These investigations are needed in cases which are not clearly anal bleeding. Furthermore many patients who are not clearly anal bleeding would require referral to a colorectal surgeon and occasionally to a gastroenterologist (if the suspicion is high that the patient suffers from inflammatory bowel disease)

Bleeding PR flowchart


Clinical features of Anal Bleeding:

Anal bleeding (meaning bleeding coming from the anal canal only) is characteristically on the tissue paper ONLY and is described as pink or bright red in colour. Anal canal bleeding, not uncommonly cause bleeding into the toilet or on the surface of faeces, but then it would not be possible to distinguish this from bleeding per rectum.

Examination should always include a thorough inspection of the perianal area for any skin lesions such as perianal dermatitis or the external opening of fistulae as well as a thorough digital rectal examination of the anal canal and rectum. A proctoscopy is quite useful as well, but probably not mandatory at least at the initial GP consultation

Causes of anal bleeding:

1. Haemorrhoids. 2. Anal fissure 3. Bleeding from causes in the perianal skin such as anal fistulae or dermatitis (the latter usually associated with pruritis ani) 4. anal cancer

Should you believe the patient: Is it really anal canal bleeding?

Well, this is a decision that has to be made by the GP or the specialist. In general it is easy to make, if you make sure that patients understood the questions correctly. If in doubt (patient not sure, patient forgetful or unreliable), it may be necessary to err on the side of caution and treat / manage as bleeding per rectum.

Bleeding per rectum

Bleeding per rectum may be fresh bright red or dark in colour. It may be on the surface of faeces or it may be mixed within. It may or may not be associated with passing blood clots or other colorectal symptoms. it may be small in amount, moderate or massive amount causing fainting

It is thus generally possible to classify patients into different symptom groups, each suggesting different disease processes or site

1. Bight red bleeding separate from the motion or on its surface. This usually suggest a source of bleeding in the anal canal or rectum. The cause can be seen on rigid or a flexible sigmoidoscopy. Total colonic examination (Colonoscopy or barium enema) is rarely indicated. The commonest cause is internal haemorrhoids, but it may also be the presentation of rectal or rectosigmoid cancer as well as Ulcerative Colitis, especially limited distal variety (or Crohn's proctitis). It may also be the presentation of radiation proctitis, for example following radiotherapy to prostate cancer. It is perhaps more common in the last category to pass mucus as well (3, below)

2. Bright red bleeding separate from the motion or on its surface, associated with anal pain (usually severe). This mostly suggest the presence of an anal fissure. If the pain is milder, it may be secondary to subacute or acute on chronic fissure, complicated haemorrhoids, but anal canal cancer may present with some anal discomfort. Fissures associated with inflammatory bowel disease, leukaemia and TB may be painless or cause some discomfort

3. Bright red bleeding separate from the motion or on its surface, associated with mucus discharge. This in many cases is due to rectal mucosal prolapse. It also occurs with large prolapsed haemorrhoids. This presentation can be also secondary to proctitis (UC, Crohn's or radiation proctitis), rectal villous adenoma, or rectal cancer

4. Bright red bleeding mixed with the motion, but with no mucus discharge or other bowel symptoms. This may be secondary to polyps or cancer, but can also occur with segmental forms of colitis such as Crohn's disease and ischaemic colitis

5. Bright red bleeding, massive in amount. This is most frequently caused by angiodysplasia of the colon or diverticular disease. Far less commonly it may occur secondary to a large fungating cancer eroding a blood vessel. Also uncommonly upper GI sources such as duodenal ulcers may present as massive lower GI bleeding (they present far more commonly as haematemesis or melena)

6. Bright bleeding mixed with the motion and associated with mucus and with or without change in bowel habits (usually loose motions). This may be secondary to left sided colonic cancer, but is also typical of Crohn's colitis and Diverticular colitis

7. Dark bleeding per rectum mixed with the motion with or without change in bowel habits. This generally indicate that the source of bleeding may be in the splenic flexure area or proximal. Polyps & cancer are important causes. Rarely Haemorrhoids may bleed internally before defaecation and the blood which is passed later on, may look dark. Patients sometimes will describe bright red blood as dark blood confusing the doctors. Dark blood mandates full colonic examination

Does the age of the patient influence referral?

Yes & No.

The youngest colorectal cancer I have seen was a girl aged 18 years old. I have also seen a few in their 20s, more in their 30s & 40s. However most present in their 50s -90s. In short you can't be too dogmatic when it comes to age.

So what is the rational approach?. I suggest that patients above 60 need rapid access referral. those 40-60 need soon or urgent referral depending on clinical features. Patients aged 20 - 40 are probably at a lower risk (except those with HNPCC or strong family history. Blacks, asian and middle eastern have a higher incidence of colorectal cancer below the age of 40) and so if the clinical picture and a digital rectal examination suggest haemorrhoids, it may be reasonable to treat them for 2-3 weeks, but continued bleeding even in this age group mandates referral for further investigations.

Colonoscopy or flexible sigmoidoscopy?

You may come to the conclusion that the symptoms warrant a flexible sigmoidoscopy, yet the consultant arranges for a colonoscopy, why?

First and foremost, no expert is infallible. One will always err on the side of caution, if at all in doubt. In addition, a colonoscope is a more reliable instrument in examining the left side of the colon in patients with redundant colon (because of its length). Lastly, one may discover an indication for screening (e.g. family history).








Deya Marzouk, Consultant Surgeonscalpel pix