Why is there blood in my stools?

The sight of seeing blood in our stools can be very daunting and creates a lot of anxiety. It is however reassuring to know that most bleeding is from benign causes. Despite the sight of a toilet bowl splashed with blood, the blood loss is usually only a small amount and does not cause any acute ill effects.

All situations of bloody stools must be investigated with a colonoscopy (a ‘camera test’ of the colon). Important causes of bleeding such as colonic polyps or colon cancer must be excluded before attributing the bleeding to benign causes.

The common causes of bloody stools are as elaborated below. As is evident, most of the causes are benign conditions. Nonetheless, all situations of bloody stools must be investigated thoroughly.

Haemorrhoids (Piles)

“Piles” is the layman term while “Haemorrhoids” is the medical term. There are misconceptions as to what constitutes haemorrhoids, and this is explained further in this article.

Haemorrhoids are enlarged ‘tissue cushions’ in the anus that are filled with blood vessels. It is easy to imagine how haemorrhoids can easily bleed when they get abraded by hard stools. Haemorrhoidal bleeding is usually painless.

There are four different grades of haemorrhoids which are dependent on the size. The higher-grade haemorrhoids can manifest as a lump at the anus that comes out during the passage of motion. It is a common misconception to identify Perianal Skin Tags (small pieces of extra skin at the anus) for haemorrhoids.

Of note, haemorrhoidal bleed may mimic colon cancer bleed but haemorrhoids per se do not transform into cancer nor increase the risk of developing colon cancer.

Haemorrhoids usually cause pain if they are trapped outside the anus for prolonged periods with consequent swelling.

 

Anal Fissure / Tear

An anal fissure is a tear of the lining of the anus. It is associated with a small skin tag that is often mistaken for a haemorrhoid. Bleeding from an anal fissure is often associated with excruciating anal pain that can last for hours. This is in contrast with hemorrhoidal bleeding that is often painless.

Anal fissures usually develop after the passage of hard stools, particularly in a subgroup of susceptible individuals with high resting anal sphincter pressures.

 

Diverticular Bleed

Colonic Diverticular Disease is a benign condition of the colon whereby multiple outpouchings of the colon occur as one ages (usually after the late 40s or early 50s). It is noteworthy that we are diagnosing an increasing number of cases of diverticular disease in individuals as young as their late 30s or early 40s. One hypothesis is the advent of a ‘Western’ diet with relatively lower fibre intake.

The colonic diverticular disease usually presents as multiple episodes of acute bleeding within a short duration of a few hours or a day. The bleeding is usually of large amounts requiring multiple trips to the toilet. The usual scenario is the initial passage of blood mixed with stools, with subsequent episodes of passage of blood only. Blood clots can often be present. There is usually some abdominal discomfort due to the rapid passage of blood through the colon. Note that the nature of the bleeding of diverticular disease is very different from that of haemorrhoids, which usually occur only during bowel movements.

Colonic diverticular bleeding is potentially life-threatening and needs an early referral to a tertiary hospital and blood transfusions and other life-saving interventions, including emergency colon resection surgery.

The colonic diverticular disease does not develop into colon cancer nor does it increase the risk of developing colon cancer.

Colonic Polyps and Colon Cancer

Colonic polyps are the precursors of colon cancers. Polyps must be detected and removed during a colonoscopy to prevent future cancer development.

Large polyps or tumours in the rectum and lower colon can give rise to bloody stools. In addition, colorectal tumours can also cause a change in bowel movement habits or watery stools. A colonoscopy will be able to accurately exclude the presence of polyps or cancer and yet allow removal of polyps.

Inflammatory Bowel Disease

Inflammatory bowel disease is usually divided into two distinct conditions, Crohn’s disease and Ulcerative colitis.

Individuals with either of these diseases tend to develop symptoms much earlier in life, usually around the 20s to 30s. The most common symptoms include bloody stools, loss of weight and generalised loss of energy.

Early diagnosis with specialised stool tests and a colonoscopy with tissue biopsy is essential. Both conditions carry an increased risk of development of colon cancer. Initial prompt medical treatment can achieve good control, though a proportion of patients with either condition will require some form of surgery in their lifetime.

Non-Colonic Conditions

Bleeding from portions of the gastrointestinal tract outside of the colon can also be the cause of bloody stools. The common sites of bleeding include the stomach, of which peptic ulcers are the most common cause. It is important to take note that peptic ulcers often develop in high-stress individuals or individuals with stressful jobs, in individuals on long term non-steroidal anti-inflammatory painkillers (e.g. Naproxen, Diclofenac and Mefenamic acid) or with a history of Helicobacter.pylori in the stomach.

A rare source of bloody stools is the small intestine, of which the average human has over 5m in length. Possible causes include tumours, vessel malformations (angiodysplasia), ulcers or the presence of a Merkel’s diverticulum. Due to the length of the small bowel and the relative inaccessibility to endoscopic (‘scope’) evaluation, specialised tests are needed to locate the source of small bowel bleeding.

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