What Causes Constipation?

Constipation does not simply mean opening the bowels infrequently. Hard stools, excessive straining, difficulty in passing the stool, and the feeling that the bowel has not emptied completely afterwards are also among the symptoms of constipation.

Bowel habit varies from person to person. Not opening the bowels every day does not therefore mean constipation on its own.

Constipation has many causes, and most of them have nothing to do with cancer.

What are the symptoms of constipation?

People with constipation may have:

• Opening the bowels fewer than three times a week
• Hard or lumpy stools
• Excessive straining
• Difficulty in passing the stool
• A feeling that the bowel has not emptied completely
• A sensation of blockage while opening the bowels
• Bloating and discomfort in the abdomen

Some patients open their bowels every day and yet are constipated because of difficulty in passing the stool.

What are the commonest causes of constipation?

Diet and way of life

Insufficient fibre intake, in some people an insufficient fluid intake, a sedentary life, and continually putting off the need to open the bowels can all contribute to constipation.

Changes in bowel habit may also be seen with advancing age.

Medicines

Certain medicines can cause constipation.

These may include some:

• Painkillers, opioids in particular
• Iron preparations
• Antidepressants
• Anticholinergic medicines
• Certain calcium-containing products
• Certain blood-pressure medicines

If the constipation appeared after starting a new medicine, it may be useful for a doctor to review the medicines being taken.

Do not stop medicines you take regularly without consulting your doctor.

Can other diseases cause constipation?

Yes.

An underactive thyroid gland, diabetes, certain neurological diseases and metabolic disorders can cause constipation.

Structural disease of the large bowel such as a narrowing or a tumour must also be borne in mind, particularly in newly started constipation.

Can the bowel work slowly?

In some people the stool moves through the large bowel more slowly than normal. This is called slow-transit constipation.

In these people the frequency of opening the bowels may be markedly reduced, and the standard changes to way of life may not always be enough.

What causes difficulty in passing the stool?

In some patients the problem is not so much that the bowel works slowly, as that the muscles which act during defaecation cannot work in a co-ordinated way.

Normally, certain muscles in the pelvic floor and the anal region have to relax while the bowels are being opened. When this co-ordination is disturbed, the patient may:

• Stay in the lavatory for a long time,
• Strain a great deal,
• Feel that the stool is caught on the way out,
• Feel afterwards that they have not emptied completely.

In these situations using a laxative alone may not be enough. Where necessary, anorectal manometry, a balloon expulsion test and other pelvic-floor investigations can be carried out.

In suitable patients, biofeedback treatment may help.

What helps constipation?

The treatment of constipation varies according to its cause. In many people, way of life and diet are addressed first.

A diet rich in fibre

Vegetables, fruit, whole grains and pulses can increase fibre intake.

Increasing the amount of fibre suddenly can, however, increase wind and bloating in some people. It may therefore be more appropriate to increase fibre gradually.

Take enough fluid

Drinking enough water is important, particularly in people whose fluid intake is insufficient.

It should not be thought, however, that drinking more water than is needed will by itself cure all constipation.

Keep moving

Regular physical activity can support general bowel function.

Do not put off going to the lavatory

Continually putting off the urge to open the bowels can disturb bowel habit over time.

Establishing a regular lavatory habit, taking advantage of the bowel’s natural activity after breakfast in particular, may help in some people.

Can medicines for constipation be used?

They can be used where required.

Depending on the type of constipation:

• Fibre supplements
• Osmotic laxatives
• Stimulant laxatives
• Different medicines that soften the stool or affect bowel movement

may be used.

The same medicine is not suitable for every constipation.

In constipation that is long-standing or does not respond to standard treatment, rather than continually trying different laxatives, it is sounder to establish the cause of the constipation.

When does constipation matter?

Medical assessment is particularly important if any of the following is present:

• Newly started and persisting constipation
• Blood in the stool
• Black stools
• Unexplained weight loss
• Anaemia
• Severe or steadily increasing abdominal pain
• Persistent vomiting
• Marked swelling of the abdomen
• Inability to pass wind or stool
• A persistent and marked change in the calibre of the stool
• A family history of colon cancer or significant bowel disease
• Constipation that persists despite treatment

Where severe abdominal pain, vomiting, marked abdominal swelling and an inability to pass wind or stool are present together, urgent assessment may be required for bowel obstruction.

Is colonoscopy needed in constipation?

Colonoscopy is not needed in every patient with constipation.

The patient’s age, whether the symptoms are newly started, alarm symptoms, family history and the need for colon cancer screening are all assessed together.

Colonoscopy can be carried out in patients in whom it is judged necessary.

How is the cause of constipation investigated?

The patient’s bowel habit, the form of the stool, the medicines being taken, the pattern of eating and any accompanying diseases are assessed first.

Where required, investigations such as:

• Blood tests
• Colonoscopy
• Colonic transit studies
• Anorectal manometry
• Balloon expulsion test
• Defaecography

may be used.

Not every patient needs all of these tests.

Remember

Constipation is not just “not going to the lavatory often”.

The hardness of the stool, excessive straining, difficulty in passing it and the feeling of incomplete emptying are also important parts of constipation.

In constipation that is long-standing or does not respond to treatment, rather than simply using a laxative, it is important to establish the cause and to plan the treatment accordingly.