The bowel is the part of the gastrointestinal (digestive) system that extends from the stomach to the anus. It includes the small bowel or small intestine and the large bowel or large intestine (which incorporates the colon and rectum). The bowel is responsible for removing solid waste (left over from food that is eaten) from the body in the form of poo (more formally referred to as stools or faeces). Passing a stool is called a bowel movement or motion.
Fibre in food adds bulk to the stool helping it to pass through the bowel more easily. Staying hydrated also helps bowel function. Not drinking enough fluid can lead to dehydration, which causes the bowel to absorb more fluid from the solid waste, drying it out, making the stool harder and more difficult to pass. Normally people have between 1-3 soft bowel movements every day to one every other day. Constipation is generally defined as fewer than three bowel movements per week.
Constipation occurs when the stool moves too slowly through the bowels or cannot be easily expelled (passed) from the rectum, which may cause the stool to become hard and dry.
Occasional temporary (acute) constipation is common and is usually related to dietary and lifestyle factors. However, some people experience chronic constipation that interferes with their daily tasks. Chronic constipation is constipation that persists for several weeks or longer.
There are many causes of chronic constipation, including:
- Blockages in the colon or rectum: caused by a bowel obstruction, anal fissure, bowel cancer, rectal cancer, or when the wall of tissue that separates the rectum from the vagina weakens, allowing the vaginal wall to bulge (rectocele)
- Narrowing of the colon (bowel stricture), which can be caused by inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis
- Functional gastrointestinal disorders, in which the bowel behaves abnormally but without evidence of injury or disease, e.g., irritable bowel syndrome
- Problems with pelvic muscles involved in having a bowel movement: including having pelvic muscles that are weak or that don’t contract and relax properly and an inability to relax the pelvic muscles
- Neurological problems affecting the muscles in the colon and rectum: caused by multiple sclerosis , Parkinson’s disease, brain or spinal cord injury, and stroke
- Imbalances of hormones that help maintain the body’s fluid balance: caused by diabetes mellitus, pregnancy, and an underactive thyroid gland (hypothyroidism).
Complications of constipation include haemorrhoids (piles), which can result from repeated straining to have a bowel motion; tears in the skin of the anus (anal fissure); faecal impaction, which is a hardened stool that becomes lodged in the colon and can’t be passed; and rectal prolapse, which is when straining to have a bowel motion causes some of the intestine to protrude from the anus.
Factors that may trigger or increase the likelihood of becoming constipated include:
- Lack of dietary fibre, i.e., fruit, vegetables, and cereals
- Insufficient fluid intake
- Excessive consumption of coffee, tea, or alcohol (which dehydrate the body)
- Excessive consumption of constipating (low fibre) foods, e.g., processed foods, meat, and dairy products
- Ignoring the urge to have a bowel movement
- Not exercising/having low levels of physical activity
- Changes in diet or daily routine
- Psychological issues, e.g., stress, anxiety, depression, and eating disorders
- Certain medications, e.g., some antidepressants and blood pressure-lowering drugs, opioid drugs (codeine and morphine), antacids, iron supplements, and some illicit drugs
- Using laxatives on a regular basis.
Signs and symptoms
Constipation symptoms and signs include:
- Passing fewer than three stools a week
- Having dry, lumpy, or hard stools
- Straining to a have bowel movement
- Having a feeling that there's a blockage in your rectum that is preventing a bowel movement
- Having a feeling that a stool can’t be completely emptied from your rectum.
You should see your GP if you experience or observe the following:
- Blood in stools
- Constipation that alternates with diarrhoea
- Constipation that continues after making dietary changes or trying other remedies
- Abdominal pain or bloating with constipation
- Weight loss without trying to lose weight.
Initial diagnosis of constipation involves a review of a person’s symptoms, general physical examination, and digital rectal examination. The following tests and procedures may be used to diagnose chronic constipation and to identify the cause of constipation:
- Blood tests to reveal anaemia that might be associated with rectal bleeding
- Thyroid function tests to rule out hypothyroidism
- Examination of the bowels (sigmoidoscopy and colonoscopy) using a long, thin, flexible tube tipped with a video camera
- Anal sphincter muscle function tests to measure the coordination and efficiency of the muscles that move the bowels
- Colonic transit study to evaluate how well food moves through the colon, in which a special marker is swallowed and its progress passing through the bowels is followed using X-rays
- Defecology studies, using X-rays or MRI to look for signs of rectal muscle dysfunction and diagnose other problems, such as rectocele and rectal prolapse.
For most people with constipation, initial treatment involves diet and lifestyle changes to speed up the movement of a stool through the bowels. These changes include:
- Increasing intake of dietary fibre and fluid
- Exercising daily
- Reducing consumption of constipating foods and beverages.
If dietary and lifestyle changes don’t result in relief of constipation, medications or surgery may be recommended. Medications that may be prescribed by a doctor to treat constipation include:
- Bulk-forming laxatives (fibres; e.g. psyllium, sterculia): absorb liquid in the intestines and swell to form a soft bulky stool, the presence of which stimulates bowel movement
- Emollient stool softener laxatives (e.g. docusate sodium): moisten the stool by drawing water from the intestines and are used with patients who should avoid straining during a bowel movement
- Enemas and suppositories (e.g. sodium citrate, glycerol, phosphate enemas): help to soften stools and produce a bowel movement.
- Osmotic laxatives (e.g. magnesium hydroxide, lactulose): draw fluid into the bowel from surrounding tissues, resulting in a soft stool mass and increased bowel movement
- Stimulant laxatives (e.g. sennoside B, bisacodyl): cause the intestines to contract, which promotes movement of stools through the bowels
- Rapid-acting lubricant laxatives (e.g. paraffin liquid): lubricate the intestine to facilitate passage of stool by reducing water absorption from the intestine, which allows the stool to remain soft.
- Prokinetic agents (e.g, prucalopride): trigger and normalise bowel motions. Their use is restricted to people with severe constipation.
Taking laxatives is not recommended without medical supervision. They should not be used on a regular basis and should be stopped once the constipation has resolved. When taken regularly laxatives can reduce the natural muscle tone of the bowel and hence become a risk factor for constipation.
Surgery is generally restricted to the evaluation of underlying causes but may be required for people with chronic constipation caused by a bowel blockage, rectocele, anal fissure, or bowel stricture that has not responded to other treatments. For people who have abnormally slow bowel movements, and have tried other treatments without success, surgical removal of part of the intestines may be an option.
Simple changes to diet and lifestyle can help to prevent constipation:
- Increase intake of dietary fibre, e.g., wheat bran, oats, linseed, prunes, broccoli, rhubarb, kiwifruit, corn, and dried fruits
- Eat less processed food, dairy products, and meat, which contain low amounts of fibre
- Drink plenty of fluid, especially water, and avoid alcohol and caffeine
- Go for a daily walk or run
- Don’t delay having a bowel motion – go when you feel the urge
- Avoid straining when having a bowel motion
- Develop a regular, unhurried bowel habit
- Minimise stress and anxiety.
Further information and support
For further information and support, contact your doctor, practice nurse, or any of the following organizations.
Free phone: 0800 611 116
Free phone: 0800 933 922
Basson, M.D. (2017). Constipation (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/184704-overview [Accessed: 08/05/18]
Mayo Clinic (2018). Constipation (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/constipation/symptoms-causes/syc-20354253 [Accessed: 08/05/18]
Ministry of Health (2014). Constipation (Web Page). Wellington: New Zealand Government Ministry of Health. https://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/constipation [Accessed: 08/05/18]
O’Toole, M.T. (Ed.) (2013). Constipation. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Updated: May 2018