Rectal bleeding (for which the medical term is haematochezia) is a common symptom experienced in the general population. Rectal bleeding refers to the passage of blood from the back passage which may originate from the anus, rectum or higher up in the gastrointestinal tract. There are numerous possible causes for the passage of blood with your stool including anal fissures (tears within the anal wall), haemorrhoids, diverticulosis, colon cancer and polyps, angiodysplasias (abnormal clumps of vessels within the intestine wall) and colitis. In most cases the cause will be harmless and temporary but is important to be investigated by a doctor to exclude something serious such as cancer of your bowel. If you are older than 60 with rectal bleeding it is extremely pertinent that your see your doctor so they can perform the appropriate investigations such as colonoscopy. Further treatment then aims to stop the bleeding and treat the underlying cause.
Rectal bleeding, also known as haematochezia, refers to the passage of bright blood (often mixed with clots or stools) via the rectum. The rectum is the final 15cm of the colon (large intestine) where faeces accumulate before being expelled from the body via the anal canal. Rectal bleeding can be due to bleeding from anywhere in the lower gastrointestinal tract namely the colon, rectum or anus. Rectal bleeding is a very common complaint in the general population and affects up to 15% of adults. Unfortunately not all these people report their symptoms to their doctors which is dangerous as a small proportion of rectal bleeding is due to an underlying colorectal carcinoma. The majority of cases however will be due to a self-limiting condition affecting the anus or rectum but it is still important that you see a doctor. The severity of rectal bleeding varies widely. Some patients will only have a few small drops of blood that stain the toilet water or are detected on wiping, whilst others will pass several bowel motions containing large quantities of blood and clots. In some patients the amount of blood loss is severe enough to cause weakness, light-headedness, low blood pressure and symptoms of anaemia. In these cases hospital admission is often needed. The colour of the blood gives the doctor a clue to the likely site of origin of the gastrointestinal bleeding. Generally speaking, the closer the lesion is to the anus the brighter the blood lost. The image to the right shows fresh bleeding from a polypoid (protruding) lesion within the rectum, as seen by colonoscopy.
Bleeding from the first parts of the large intestine (the ascending and transverse colon) on the other hand will cause passage of dark red or maroon blood. Bleeding from much further up the gastrointestinal tract such as the stomach doesn’t normally cause the loss of fresh blood but produces black and tarry stools called melena. Rectal bleeding is a symptom itself and should not be confused with the term faecal occult blood. The latter has similar causes to rectal bleeding but does not result in any colour changes to the stool or presence of fresh blood in the rectum. Faecal occult (hidden) blood is only detected when stool samples are examined at a laboratory. This may be done for the purpose of investigating the cause of iron deficiency anaemia.
The most frequent causes of lower gastrointestinal or rectal bleeding include:
- Diverticular disease- Diverticulosis refers to the presence of small out-pouchings (sacks) within the wall of the intestine which affects most people to som degree by the age of 50-60 years. The precise cause for the condition is not known and it generally doesn’t cause a problem unless the pouches rupture or become inflamed (diverticulitis). Both diverticulitis and diverticulosis can cause the sudden loss of large amounts of blood via the rectum into the toilet bowl. In the latter case this blood loss is painless. Diverticular disease is the most common cause of rectal bleeding in the elderly and due to the large amount of blood loss often requires hospitalisation and blood transfusion.
- Inflammatory bowel disease- Crohn’s disease and ulcerative colitis are the most common causes of inflammatory bowel disease which are characterised by damage and inflammation of the lining of the bowel. Both these conditions can cause rectal bleeding that is often mixed with mucus in a loose stool. Lack of blood supply to area of the bowel called ischaemic colitis may also damage the wall and later lead to bleeding.
- Benign anorectal diseases (harmless diseases of the anus and rectum)- Haemorrhoids are masses or clumps (cushions) of tissue in the anal canal that contain blood vessels. If large enough they can cause mild bleeding that often presents as bright red blood on toilet paper or on the outside of the stools. Associated symptoms include discomfort and pruritus ani (itchy bottom). Anal fissures refer to painful tears in the skin lining the lower anal canal often caused by straining or constipation. Once a tear is present, later efforts to pass stool are very painful and may lead to bleeding. Fistula-in-ano refers to abnormal connections between the anus and other organs or tissues. Fistulae are typically painful and may present as abscesses or loss of bright red blood on toilet paper and the surface of the stool.
- Polyps- These are benign tumours or growths in the large intestine that can predispose to cancer. The bleeding associated with polyps tends to be mild and intermittent. Removal of polyps during colonoscopy (polypectomy) can also cause later rectal bleeding days to weeks after the procedure.
- Neoplasia- Cancer of the colon typically causes blood to be mixed with the stool. Colon cancer can also cause occult blood loss and be diagnosed following investigation of symptoms of weight loss or anaemia.
- Coagulopathy- Certain drugs that thin the blood (e.g. warfarin) or inherited clotting disorders can predispose to bleeding from the gastrointestinal tract.
- Arteriovenous malformation- Angiodysplasia refers to abnormal connections between the veins and arteries in the walls of the intestines. These vessels are prone to rupture and are a common cause of fresh rectal bleeding in the elderly.
- Very rarely rectal bleeding may originate from the upper gastrointestinal tract from an ulcer or other lesion of the stomach or small intestine. Bright red rectal bleeding will only occur in these circumstances if the blood loss is very rapid and severe, otherwise these lesions will normally produce dark stools (melena) and bloody vomit.
Rectal bleeding can be a quite alarming symptoms for patients but if you see your doctor promptly most cases can be treated and controlled. As highlighted above, the characteristics of the rectal bleeding will depend on the underlying cause. The doctor will use this information to formulate the likely site of the bleeding and the specific cause. When you go to the doctor complaining of rectal bleeding you should expect the following information to be discussed:
- Previous history of gastrointestinal bleeding.
- Past medical history or other medical conditions.
- Your current medications including NSAIDs and warfarin. Your doctor will then ask detailed questions about your symptoms including:
- Is it painful to pass stools?
- What colour is the blood? Is it bright or dark in colour?
- Is there blood mixed with the contents of the stool or is it found on its surface?
- Is blood present when you wipe yourself?
- Is blood present in the toilet pan?
Depending on your age, different conditions are more likely to cause rectal bleeding. For example a young patient with abdominal pain, rectal bleeding, diarrhoea and mucus discharge most likely has inflammatory bowel disease whilst an older patient with moderate to severe rectal bleeding is more likely to have diverticulosis or angiodysplasias. If you are older than 60 years, have a family history of colon cancer and have symptoms of fatigue and weight loss you are at much higher risk of colorectal cancer so it is extremely important that you see a doctor if you notice rectal bleeding. Some doctors may ask screening questions about rectal bleeding in all patients over 60 years to ensure that the diagnosis of colorectal cancer is not missed. Following a detailed history, the doctor will examine your abdomen, anal canal and rectum. Sometimes they may find a haemorrhoid or fissure when inspecting the anus that may be the cause of the bleeding. However, further investigation is always needed to examine the entire colon to make sure no other serious conditions are present that may also be contributing to the bleeding. The following investigations may be performed:
- Anoscopy- This refers to the insertion of a small, lubricated tube of three inches in length, into the anal canal and rectum. When the tube is withdrawn the usual site of haemorrhoids and fissures is visualised.
- Flexible sigmoidoscopy- The sigmoidoscope is a flexible tube with a light and a camera that is inserted via the rectum to view right up to and including the descending colon. This can be performed with minimal bowel preparation. This investigation can detect polyps, cancers and diverticula (out-pouchings) within the rectum, sigmoid and descending colon.
- Colonoscopy- This is probably the most widely used investigation for both rectal bleeding and occult bleeding as it allows examination of the entire colon and rectum to detect polyps, carcinoma, diverticulosis, ulcerative colitis, Crohn’s colitis, ischaemic colitis and angiodysplasias.
- Blood tests such as a full blood count can help to identify iron deficiency anaemia which suggests a long-term cause for the bleeding.
- Other investigations such as radionuclide scans (using targeted red blood cells) and angiography (x-ray studies of the blood vessels) may also be performed in some cases.
Initially treatment will focus on ensuring you are stable and replacing some of the blood that you have lost. If you have severe symptoms of anaemia or appear shocked (cool, clammy skin, heart racing, low blood pressure) you will most likely need to be treated in hospital so you can receive fluids via a drip in your arm or be given a blood transfusion if necessary. If you are generally well, all the tests and investigations could potentially be organised by your GP as an out-patient. They may give you some iron supplements in the meantime. The next aim is to identify the cause of your bleeding to allow treatment. As fore mentioned colonoscopy is the investigation of choice and will identify the majority of sources for bleeding. In addition, colonoscopy can help treat some of these conditions by cutting away bleeding polyps or burning (cauterising) abnormal vessels and bleeding diverticula. If this fails to locate the site of bleeding a visceral angiogram may be done which looks at the specific vessels and can be used to guide injection of substances that cause blood vessels to constrict and stop bleeding. These agents are injected through a thin tube (called a catheter) into the bleeding vessel. If both these treatments fail, surgery may be required. Hopefully the site of bleeding would have been identified so the surgeon can remove only a small part of the damaged area, however sometimes large portions of bowel need to be removed to stop bleeding. Other causes of mild rectal bleeding such as haemorrhoids or anal fissures can often be treated by local measures such as anesthetic gels, creams, injections and stool softeners. If these measures fail local surgery may be needed.