Constipation

We have all experienced the strain and discomfort of constipation at some stage of our lives as a result of changes in diet, dehydration or reduced activity, but if it persists a specific cause should be sought so that long-term complications do not occur.

Normal bowel activity can vary from two or three times a day to two or three times a week, or even once a week in some individuals. Constipation increases with age and is far more common in the elderly than the young.

To be medically significant, constipation must cause discomfort in the abdomen, pain around the anus, bleeding, tears (both pronunciations of the word are appropriate), piles or another problem.

Constipation

Hard dry motions are usually due to inadequate fluid intake, eating too much junk food with too little fibre, or lack of exercise. It may also be due to repeatedly ignoring signals to pass a motion and allowing the bowel to become distended, which reduces the urge to eliminate and the problem becomes self-perpetuating.

The major complications of persistent constipation are piles (bleeding under the skin caused by over stretching of the anus and straining), anal tears (fissures) and megacolon (an over dilated lower end of gut that cannot contract properly). All these problems can worsen constipation as well as being a result of the problem, as patients with piles and tears are reluctant to pass motions because of pain, while megacolon prevents normal lower bowel contraction to move faeces along.

Bedridden patients often find they become constipated due to the lack of activity and body movement. Even a healthy person who becomes less active because of a broken leg or bad dose of the flu will suffer the same effects.

Changes in diet, particularly if more protein and less fibre are suddenly eaten, and lack of fluid (dehydration) will both cause the faeces to harden and dry.

In the last three months of pregnancy, many women find that constipation becomes a problem as the growing baby puts pressure on the bowel.

A prolapse of the bowel occurs when it bulges forward into a woman’s vagina, or slides out through the anus due to weakening of the support structures with pregnancy or age. Straining to pass a motion only worsens the prolapse without moving the faeces.

Many different medications can have constipation as a side effect. Examples include codeine, narcotics (e.g. morphine), antacids, anticonvulsants (for epilepsy and fits), antidepressants, diuretics (fluid tablets) and iron.

Less common causes of constipation include hypothyroidism (underactive thyroid gland), tumours or cancers of the last part of the large intestine, irritable bowel syndrome, depression, neuroses and psychiatric disturbances, Hirschsprung disease, diabetes mellitus, persistent high levels of calcium in the blood stream (hypercalcaemia) from kidney or parathyroid gland disease, and abnormal balances of sodium, potassium or chloride in the blood.

Extensive investigations (e.g. colonoscopy, CT sacn) may be necessary to determine cause in persistent cases.

Treatment of constipation should be aimed at treating the underlying cause if possible. Dietary methods are the next choice, and only if neither is possible should laxatives or other medications be used.

Patients should change their diet by avoiding white bread, pastries, biscuits, sweets and chocolates, and adding plenty of fluids and fibre containing foods such as cereals, vegetables and fruit. If necessary, fibre supplements may be used.

Laxatives are the next step, but dependence can develop rapidly. They vary in effectiveness and strength, but the weakest ones (e.g. paraffin, other oils, senna and cascara) should be tried first. As a last resort, enemas may be used to clear out the lower gut.

Long term unrelieved constipation may result in megacolon.

Patients using long term narcotics for severe pain may be helped by using methylnaltrexone.

The prognosis depends on the cause, but the condition can usually be well managed by appropriate treatment.

(Last modified: 5th Nov 2014)

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