Blood in the stools is always abnormal and should be properly assessed by a doctor.
Blood may manifest in various forms, from fresh red blood, to dark red blood, to black-coloured stools, to blood that cannot be detected with the naked eye. This is an indicator of the site of bleeding within the gastrointestinal tract and helps to direct the mode of investigation. Blackcoloured stools point to a possible source of bleeding within the stomach or small intestines (ie the upper gastrointestinal tract), while fresh or dark red blood suggest a possible source within the colon (or lower gastrointestinal tract).
The volume of blood in the stools determines the urgency of investigation as a large amount of blood being expelled per rectum may result in severe anaemia that may be life-threatening. On the other hand, even a small amount of blood in the stools may be due to underlying colorectal cancer and also warrants early investigation.
What are the causes of per rectal bleeding?
Common causes of blood in the stools include:
a. Haemorrhoids: commonly known as piles. They are enlarged and engorged blood vessels in and around the anus, and may be associated with pain, itching or sensation of a lump.
b. Diverticular disease: sac-like protusions of the intestinal wall that usually do not cause any symptoms. However, bleeding from diverticular disease may sometimes be massive and life-threatening in nature.
c. Colitis: inflammation of the wall of the large intestines, that can be due to infection or insufficient blood flow (ischaemia). The elderly are most often the ones affected by ischaemic colitis, due to their underlying medical conditions.
d. Angiodysplasia: a vascular abnormality of the gastrointestinal tract that is due to degeneration of blood vessels. The bleeding is painless, and can sometimes be massive. Though the bleeding stops spontaneously in more than 90% of patients, it is often recurrent.
e. Colorectal cancer: the most common cancer in Singapore. It may also be associated with a change in bowel habits or loss of weight and appetite. The diagnosis of this may sometimes be confounded by the presence of haemorrhoids, another common occurrence in the Singapore population.
What tests should I go for?
All patients showing symptoms of per rectal bleeding should ideally undergo a colonoscopy for evaluation of the large intestines. This is in addition to a digital rectal examination and a direct visualisation of the lower rectum and anus with a proctoscope that your doctor can perform in the outpatient clinic.
A colonoscopy involves inserting an optical endoscope via the anus into the large intestines to inspect the inner lining of the colon for any of the conditions mentioned earlier. It may be done under sedation and is a relatively safe procedure. Pre-endoscopic preparation with bowel cleansing medications is required.
Alternative investigations include computed tomography (CT) colonography or a CT mesenteric angiography in cases of massive bleeding.
The best modality of investigation should be discussed with your doctor.
The treatment of rectal bleeding depends on the cause of the bleeding. Bleeding due to diverticular disease, colitis or angiodysplasia may resolve spontaneously without intervention. However, recurrent bleeding may require endoscopic therapy, and severe massive life-threatening bleeding may sometimes even require surgery.
Haemorrhoids are generally treated with a combination of lifestyle and dietary advice, medications and/ or rubber band ligation of the haemorrhoids. This is done in the outpatient clinic. Surgery may be performed if the bleeding is recalcitrant in spite of medical therapy.
Bleeding as a result of colorectal cancer should be managed with surgery for the primary tumour.