Constipation: Introduction, Incidence, Causes, Diagnosis, Management and Treatment

Introduction

Over 90% of people in Western population defecate between three times a day and once every 3 days. It is clear, therefore, that to base a definition of constipation on frequency alone is problematic. What is perceived to be constipation by one individual may be normal to another? Most definitions of constipation include infrequent bowel action of twice a week or less that involves straining to pass hard feces and which may be accompanied by a sensation of pain or incomplete evacuation. A pragmatic definition would simply be the passage of hard stools less frequently than the patient’s own normal pattern.

Incidence

Constipation affects all age groups but is more common in the elderly:

• 20% of elderly people,
• 8% of middle-aged and
• 3% of young people,

while 5-10% of children are affected most of them are formula fed babies who seek medical advice for constipation. In the elderly, poor diet, insufficient intake of fluids, lack of exercise, concurrent disease states and use of drugs that predispose to constipation have all been identified as contributory factors. Constipation is more common in women than men, It is, however, common in late pregnancy (up to 40% of women) due to increased circulating estrogens, reduced gastrointestinal motility and delayed bowel emptying caused by displacement of the uterus against the colon.

Causes Of Constipation

The remains of undigested food are swept along the gastrointestinal tract by waves of muscular contractions called peristalsis. These peristaltic waves eventually move the feces from the colon to the rectum and induce the urge to defecate. Normally there is a net uptake of fluid in the body. In such situations where absorption of sugars and amino acids increases, this will generally lead to constipation, whereas a net secretion will result in diarrhea. Agents that alter intestinal motility, either directly or by acting on the autonomic nervous system, affect the transit time of food along the gastrointestinal tract. Since the extent of absorption and secretion of fluid from the gastrointestinal tract generally parallels transit time, a slower transit time will lead to the formation of hard stools and constipation. Motility is largely under parasympathetic (cholinergic) control, with stimulation bringing about an increase in motility while antagonists such as anticholinergics, or drugs with anticholinergic side effects, decrease motility and induce constipation. Drugs also induce constipation which includes Opioids cause constipation by maintaining or increasing the tone of smooth muscle, suppressing forward peristalsis, raising sphincter tone at the ileocaecal valve and anal sphincter, and reducing sensitivity to rectal distension. This delays passage of feces through the gut, with a resultant increase in absorption of electrolytes and water in the small intestine and colon. For convenience, many classify as originating from within the colon and rectum, or externally. Causes directly attributable to the colon or rectum include obstruction from neoplasm, Hirschsprung’s disease (absence of neurons in the diseased segment), outlet obstruction due to rectal prolapse or damage to the pudendal nerve, typically during childbirth.

Causes of Constipation outside the Colon Include

• poor diet,
• inadequate fiber intake,
• inadequate water intake,
• excessive intake of caffeine,
• use of medicines with constipating side effects or
• systemic disorders such as hypothyroidism,
• diabetic autonomic neuropathy,
• spinal cord injury,
• cerebrovascular accident,
• multiple sclerosis or Parkinson’s disease.

Differential Diagnosis for Constipation

To aid diagnosis, questions need to be asked about the frequency and consistency of stools, nausea, vomiting, abdominal pain, distension, discomfort, mobility, diet and other concurrent symptoms or disorders the patient may be experiencing. It may also be necessary to ask about access to a toilet or commode. The individual with limited mobility may suppress the urge to defecate because of difficulty in getting to the toilet. Likewise, lack of privacy or dependency on a nurse or carer for toileting may result in urge suppression that precipitates constipation or exacerbates an underlying predisposition. For patients with unexplained constipation with abdominal pain and the passage of blood or mucus, and long-standing constipation unresponsive to treatment require further investigation.

Investigations Include

• sigmoidoscopy/colonoscopy,
• barium enema,
• biochemical mon
• full blood count itoring including thyroid function tests.

General Management

For uncomplicated constipation, education and advice on diet and exercise are prior in the management of constipation. Typically this advice will include reassurance that the individual does not have cancer, that the normal frequency of defecation varies widely between individuals, and that mild constipation is not in itself harmful.

Non-Drug Treatment

It is advocated as the first-line therapy for all patient groups, except those who are terminally ill. This mostly includes advising the patient on increasing intake of fluid at the same time as reducing strong or excessive intake of tea or coffee, since these act as a diuretic and serve to make constipation worse. It is generally recommended that fiber intake in the form of fruit, vegetables, cereals, grain foods, wholemeal bread, etc. be increased to about 30g/day. Such a diet should be tried for at least 1 month to determine if it has an effect. Most will notice an effect within 3–5 days. Patients who increase their fiber intake must also be advised to drink 2L of water a day.

Drug Treatment

Drug treatment is indicated where there is fecal impaction, constipation associated with illness, surgery, pregnancy, poor diet, where the constipation is drug induced, where bowel strain is undesirable, and as part of bowel preparation for surgery. The various laxatives available can be classified as bulk forming, stimulant, osmotic and fecal softeners.