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Slow Colonic Transit

Constipation is a descriptive term for passage of hard difficult to pass stools. Stools may be passed in frequently or often, but are typically hard, pellety, and, difficult to pass without discomfort. Constipation, the development of hard and difficult to pass stools is different from disordered defaecation, but often the two may arise in tandem. Disordered defaecation is a descriptive term for a difficulty with the “mechanics” of passing a stool, often because of a failure of the normal sequence of muscle relaxation within the pelvic floor or the anal canal on straining to pass a stool.


Hard difficult to pass stools usually arise as a result either of dietary indiscretion or natrurally slow large bowel (colonic) transit. One of the key roles of the large bowel is to absorb a proportion of the remaining water from the fluid residue which enters the large bowel from the small bowel once the greater part of nutrients have been digested. The absorption of this liquid in normal circumstances leads to the production of soft but formed stools which should be easy to pass without pain or discomfort. However if the colon is excessively long  (some people are born with longer colon’s than others)or transit through the colon is slow, either as a result of drugs, such as opiates or anti-diarrhoeals, or in-activity (as often arises following surgery or illness) then the faecal material has more time for the salt and water within it to be absorbed. As a result more water is absorbed and the stool becomes harder firmer and often uncomfortable to pass.


Treatment should start by examining lifestyle first. Diet and exercise are important in maintaining normal gut function. The diet should include a broad range of plant based material, beans, nuts, fruit and vegetables. Although some vegetables (particularly those containing fermentable carbohydrates) may cause significant wind and bloating potentially exacerbating symptoms in those with irritable bowel syndrome (IBS), fibre is key to helping retain water within the stool. If pain and bloating are significant problems in this context it is worth considering getting the help of an appropriately trained dietician with an interest in gastro-intestinal disease. People need to eat sufficient , but it is no good having fibre without enough fluid! Fluid intake is also key to preventing constipation. Most people should aim to drink at least 40ml/kg body weight per day. For a 50kg woman that’s 2 litres a day for a 90kg man that is nearer 3.5 litres. Activity is also key to encouraging bowel movement. Many people find their constipation worsens if they reduce their activity and some patients report their constipation began during a period of immobility either in hospital or when unwell at home.


If lifestyle modification is not possible or is insufficient to improve things then medication in the form of laxatives should be considered. These come in a number of forms. In general long-term, regular use of senna should be avoided. Most patients start by using a stool softener such as movicol, laxido or lactulose. These may cause bloating and abdominal discomfort for some in which case alternatives may be sought. Nevertheless if they are tolerated it is best to try and establish a regular dose that best suits the individual patient. Taking laxatives in large doses when things are “blocked” often leads to loose stools and then patients stop until things are blocked again leading to an uncomfortable oscillation between constipation and diarrhoea. It is generally beeter to try and find a regular dose of laxatives that keeps the patient on an “even keel”.

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