By Dr Anirban Banerjee, MS, MRCS (Consultant Surgeon)
Seeing blood in the toilet, on the surface of your stool, or with wiping after a bowel movement is common and very frightening at the same time. The first thing that comes to mind is whether it is because of cancer. You will be relieved to know that most of the causes of such rectal bleeding are neither life-threatening nor because of cancer. Common causes include haemorrhoids and anal fissures. However, the only way to be certain of the cause is to be evaluated by a doctor without delay.
What are the sites of bleeding from the gut?
Bleeding can come from anywhere in the intestine. As a general rule:
◊ Bleeding from the anus or low down in the rectum – the blood tends to be bright red and fresh. It may not be mixed in with faeces but instead you may notice blood after passing faeces, or streaks of blood covering faeces.
◊ Bleeding from the colon – often the blood is mixed up with faeces (motions or stool). The blood may be a darker red. For example, bleeding from diverticula disease, or from a bowel tumour.
◊ Bleeding from the stomach or small intestine – the blood has far to travel along the gut before it is passed out. During the time it takes to do this the blood becomes altered and dark and mixes with faeces. This can make your faeces turn a black or plum colour; this is called ‘melaena.’
What are the causes of rectal bleeding?
Seeing a small amount of blood after wiping, on the outside of your stool, or in the toilet is most commonly caused by haemorrhoids or an anal fissure.
Haemorrhoids – Hemorrhoids are swollen blood vessels in the rectum or anus that can be painful, itchy, and can sometimes bleed. Painless rectal bleeding with a bowel movement is a common symptom of haemorrhoids. Bright red blood typically coats the stool or blood may drip into the toilet or stain toilet paper.
Anal fissure – An anal fissure is a tear in the lining of the anus, the opening where faeces are excreted. Anal fissures can cause bleeding and a sensation of tearing, ripping, or burning during or after a bowel movement.
Diverticula – A diverticulum is a small pouch with a narrow neck that protrudes from the wall of the gut. Diverticula mean more than one diverticulum. They can develop on any part of the gut (intestines), but usually occur in the colon. A diverticulum may occasionally bleed.
Polyps – A bowel polyp (adenoma) is a small growth that sometimes forms on the inside lining of the colon or rectum. Most develop in older people. Polyps are benign (non-cancerous) and usually cause no problems. However, sometimes a polyp bleeds and can turn cancerous.
Cancer – Cancer of the colon and rectum are common cancers in older people. They sometimes affect younger people. Rectal bleeding is one symptom that may occur.
Apart from these causes inflammation and infection of the intestine sometimes may be the cause of bleeding.
What should I do if I have rectal bleeding?
If you have bleeding from the rectum consult a doctor without delay. Sometime bleeding may be profuse and you can feel dizzy, collapse or feel generally unwell. Some people assume that their rectal bleeding to be due to haemorrhoids (‘piles’) and do not get it checked. Haemorrhoids are perhaps the most common cause of rectal bleeding. However, you should not assume the bleeding is coming from a haemorrhoid unless you have been properly assessed by a doctor.
How is the rectal bleeding evaluated?
The evaluation of rectal bleeding depends upon your age, symptoms, and past medical history. A doctor will ask you few questions to get an idea about the possible cause of the bleeding. You will be asked about possible symptoms such as pain, colour of stool, amount of blood you have passed, and if you have diarrhoea, weight loss, or other relevant symptoms. The doctor is then likely to examine you. Sometimes, a diagnosis can be made after this. For example, if it is an anal fissure or haemorrhoid. However, tests are commonly needed to clarify the cause of the bleeding.
What tests might be advised?
It depends on the possible causes of the bleeding which may be determined by a doctor talking to you and an examination.
Anoscopy – Anoscopy allows a clinician to inspect the anus and lower rectum. It can be done in the office and does not require sedation.
Sigmoidoscopy – During a sigmoidoscopy, a clinician can examine the rectum and most of the lower large intestine. Sigmoidoscopy can be done without sedation
Colonoscopy – A colonoscopy is a test where an operator (a doctor or nurse) looks into your colon.
A colonoscopy is a thin, flexible telescope. It is passed through the anus and into the colon. It can be pushed all the way round the colon as far as the caecum (where the small and large intestines meet).The colonoscope contains fibre optic channels which allow light to shine down so the operator can see inside your colon.
Should I worry about rectal bleeding?
While most rectal bleeding is caused by the non-serious causes mentioned above, bleeding can also be caused by cancerous or precancerous conditions. Precancerous polyps near the end of the colon can mimic bleeding from haemorrhoids. These are generally present in the colon for years before they become cancerous, and they can be removed very safely from the colon, preventing progression to cancer.
Colon cancer may be diagnosed in patients who have ignored bleeding for years. Polyps and colon cancer become more common with age, and thus investigation of bleeding is most important, and is usually most intensive, in patients over the age of 40 to 50 years