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Constipation

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Constipation is one of the most common reasons for a patient to present to the gastroenterologist, and can have a significant impact on a person’s quality of life.  There is a common belief that a normal bowel frequency means passing a bowel motion every day.  The truth is, stool frequency varies widely from person to person.  A “normal” bowel habit is passing a stool anywhere from three times per day to three times per week!  To meet the ROME criteria for constipation, a patient must pass less than three spontaneous bowel motions per week, and have one of:

  • <3 spontaneous bowel movements per week
  • Lumpy or hard stools >/= 25% bowel motions
  • Straining >=25% of BM
  • Sense of incomplete evacuation =>25% of bowel motions
  • Sense of blockage >=25% of bowel motions

For diagnosis, symptoms must be present for three months, with onset of symptoms more than six months prior to diagnosis.  There must also be insufficient criteria to meet a diagnosis of Irritable Bowel Syndrome.

Although some patients have an identifiable cause for constipation – such as an anatomical abnormality, or another medical condition (eg hypothyroidism, coeliac disease), in the majority of cases the cause of constipation is unknown. 

When investigating and managing a patient with constipation, it is important to exclude any defecatory disorders, ie problems related to the anus or rectum that impact on a patient’s ability to empty the rectum.  Symptoms of defecatory disorders might include frequent trips back to the toilet in order to empty the rectum, the need to use digital manoeuvres to empty the rectum and difficulty wiping clean after passing a bowel motion. If unidentified and untreated, defecatory disorders can commonly lead to slow transit constipation.

Investigations into the cause of constipation may include blood tests, colonoscopy, and colonic transit studies.  Colonic transit studies can be useful to define patients who have ‘slow transit constipation’ – a condition where the motor activity of the large intestine is decreased.  The vast majority of adult patients with slow transit constipation are female. 

Treatment of constipation mostly involves a high fibre diet, use of soluble fibre supplements, and laxatives.  Exercise in itself is not an effective treatment for constipation.  The recommended daily fibre intake is 30g per day.  Most people do not achieve this target.  In fact, the average Australian consumes just 9g of fibre per day.  The consumption of fibre adds bulk to the stool, and helps to draw water in to the colon and move intraluminal contents through the colon.  Laxatives generally work by drawing water in to the colon, or stimulating motor activity of the colon by various mechanisms.  Osmotic laxatives such as Movicol Ô are often good for first line therapy.

A new change in bowel habit in patients over 50, unintentional weight loss, the appearance of blood in the stool, and a family history of colorectal cancer are all symptoms and signs that could be indicating the presence of pathology, and referral to a gastroenterologist should be considered.