Rectal bleeding is a common symptom. It might appear as bright red blood on the toilet tissue, or as a splash of blood in the toilet bowl, or as streaks of blood mixed in the stool. It may also be less obvious—sometimes bleeding in the beginning of the digestive tract may cause the stools to look black or have a tarry consistency. Small amounts of bleeding might be invisible to the naked eye and can only be picked up by a faecal occult blood test.

When is rectal bleeding something to worry about?

Fact 1: Rectal bleeding can be due to many different causes, ranging from benign to life-threatening

It can be due to an anal fissure, which is a small tear in the lining of the anus, usually caused by hard or large stools. Anal fissures typically cause pain together with small amounts of fresh blood when passing stools.

Haemorrhoids are another common cause of rectal bleeding. Also known as piles, haemorrhoids are actually swollen veins in the anus. Patients usually describe painless, bright red blood dripping into the toilet bowl when passing stools. Prolapsing haemorrhoids may bulge outside the anus during straining, then pop back inside or can be gently pushed back with a finger. Prolapsing haemorrhoids may cause itchiness or a feeling of incomplete evacuation. Although haemorrhoids are rarely dangerous, sometimes a blood clot may form in the haemorrhoids (thrombosis), or it may become stuck outside the anus despite attempts to push it back in (incarcerated), leading to severe pain.

Diverticulosis is a condition where small pouches or sacs form in the colon. When these pouches become inflamed or infected, this condition is known as diverticulitis and may cause rectal bleeding. Inflammatory bowel disease and colon inflammation (colitis) may also be a source of rectal bleeding, often occurring along with diarrhoea.

One of the most serious causes of rectal bleeding is colorectal cancer. Both cancers and benign growths (polyps) may cause only small amounts of bleeding which are not visible to the naked eye. Cancers high in the colon will cause dark or black looking stools because of altered blood. Cancers lower down the colon, or in the rectum, will cause brighter coloured blood. Bleeding in cancer may be intermittent. Because many patients also have haemorrhoids, bleeding from cancer may be dismissed as coming from the haemorrhoids, leading to a late diagnosis of cancer.

Fact 2: Rectal bleeding should be investigated

Although the pattern and type of bleeding will give clues as to its origin, it is important to see a doctor so as not to miss a serious condition. Colorectal surgeons are specialist doctors who have completed advanced training in the treatment of diseases of the colon, rectum, and anus. In addition to the bleeding, your doctor will ask about other symptoms such as fatigue, weight loss, a change in bowel habits or a family history of cancer, followed by a physical examination. In some cases, blood tests may be needed.

For a proper examination of the entire colon, a colonoscopy is a procedure where the doctor examines the inside of the entire rectum and large bowel using a thin, flexible tube with a light at its tip. As an added benefit, any polyps or growths seen during the procedure can be biopsied or even removed completely. This can be done as a day care procedure. The American Cancer Society recommends that all adults should go for colorectal cancer screening at the age of 50.

Fact 3: Early diagnosis and treatment may mean a difference between life and death

Colorectal cancer is the third most commonly diagnosed cancer worldwide in males and the second in females according to the GLOBOCAN 2018 database. The American Cancer Society Cancer Statistics Center (2014-2016) predicted that almost one in 20 (4.4 per cent) of Americans will develop colorectal cancer during their lifetime. In Malaysia, colorectal cancer is the second most common cancer according to the Malaysian National Cancer Registry Report (2012-2016).

Fortunately, colorectal cancer is preventable and curable. Nearly all cases of colorectal cancer develop from polyps. Detection and removal of polyps through colonoscopy reduces the risk of colorectal cancer. Treatment of colorectal cancers is most successful if the cancer is caught in its early stage, with a 5-year survival rate of 90 per cent for early-stage cancer and 14 per cent for late-stage cancer, according to the American Society of Clinical Oncology. Therefore, be proactive about your health and do not ignore symptoms such as rectal bleeding.

Dr Law Chee Wei is a Consultant General and Colorectal Surgeon at ParkCity Medical Centre.