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At the heart of general practice since 1960

Constipation

Professor Christine Norton answers GP Dr Peter Stott's questions on effective management strategies

Professor Christine Norton answers GP Dr Peter Stott's questions on effective management strategies


Take-home points

  • The main categories of constipation are slow colonic transit and evacuation difficulty. Slow transit may be idiopathic
  • Fears that long-term laxatives are associated with colonic damage are largely unfounded; there is no evidence of muscular or neurological damage from prolonged use
  • Immobility, anorexia, dehydration, muscle weakness leading to inadequate abdominal effort and discomfort sitting on the toilet can contribute to constipation in terminal care
  • In children it is often necessary to give long-term oral stimulant laxatives (senna) or osmotic (magnesium salts) for six to 12 months
  • Oral macrogols are licensed for relief of impaction; up to eight sachets can be dissolved in a litre of water and drunk
  • Physiotherapists and nurses can teach women with a lax pelvic floor how to evacuate effectively

1 Is it possible from the history to make a clear diagnosis of the cause of constipation and therefore decide on logical treatment?

Different people mean different things by constipation, and careful history-taking is essential to determine what symptoms are present and the impact they are causing. Myths abound. Many people think a daily bowel action is essential to health and that less frequency will cause build-up of 'toxins'.

Constipation may refer to stool consistency, shape, frequency, or difficulty with evacuation, time taken, discomfort during stool passage, a sensation of incomplete evacuation, or abdominal pain or bloating.

Two main categories are recognised: slow colonic transit and evacuation difficulty. Slow transit may be idiopathic, but is often secondary to inadequate dietary fibre and fluid, lack of exercise and repeatedly ignoring the call to stool.

Evacuation difficulty can be secondary to stool that is too hard or too soft, a poor evacuation technique (failure to relax the anus and pelvic floor because of posture, pain or muscle weakness with the descending perineum syndrome).

The two can co-exist in the same person and one may exacerbate the other. History does not always accurately discriminate.Many other factors will contribute, such as toilet access and carer availability in people with disabilities, and other diseases or medications. Some symptoms should set alarm bells ringing. Bowel cancer is the second most common cancer in the UK.

Curable if caught early, the majority still present too late for curative resection. Rectal bleeding, especially in the patient over 50, or with altered bleeding, unexplained anaemia or weight loss and a family history of bowel cancer, should lead to fast-track referral to a rectal bleeding clinic under the two-week wait rule. Even if bleeding haemorrhoids are visible, this is no guarantee that there is not also a bleeding tumour distally.

2 Like many GPs, I am wary of using laxatives in the long term. Yet often this is impractical, particularly in the elderly. What problems are associated with long-term use and how can they be minimised? Is it really possible to avoid irritant purgatives in the elderly?

Fears that long-term laxatives are associated with colonic damage are largely unfounded. The 'cathartic colon' is a common myth and there is no evidence of muscular or neurological damage from prolonged use.

The mucosal discolouration of melanosis coli secondary to senna is harmless. But the big problem with long-term laxative use is that nearly all become less effective with time. For this reason, where a patient seems likely to need long-term use, I try to find two or three different preparations that work for that patient and rotate them.

Also keep dosage to the minimum that is effective, while avoiding sub-therapeutic regular or divided doses. It is often better to give a larger dose once daily (or every alternate day or every three days) than smaller doses twice daily.

The group that do seem to get into trouble from laxative overuse are patients who abuse them as part of an eating disorder. Some anorectic patients will regularly take handfuls of stimulant laxatives for their purgative effect, often over many years. Even once the eating disorder is under control and laxative use is stopped, many are still troubled by chronic constipation.

One of the main problems with irritant laxatives is that they risk causing episodes of faecal incontinence. Because oral laxatives tend to be unpredictable as to when they work, they can leave the patient feeling vulnerable and unwilling to venture far from a toilet. As many older people feel profoundly embarrassed by the prospect of incontinence, severe social restriction can result.

3 Use of opioids both in palliative care and chronic pain management obviously causes constipation. Do you have any tips on laxative use that might help us to prevent this side-effect?

Opioids have severely constipating effects, and proactive anticipation of this is nearly always needed, with a regular planned laxative regimen. There is almost no evidence as to which laxative is most effective, but often both a softener and stimulant will be needed.

In terminally-ill patients the concerns about potentially carcinogenic properties of co-danthrusate are usually not relevant and this preparation has combined properties.

But it should not be forgotten that many terminally-ill patients will have other factors contributing to their constipation and some of these may be amenable to modification. Immobility, anorexia, dehydration, muscle weakness leading to inadequate abdominal effort, and discomfort sitting on the toilet may each contribute.

Attempting to minimise these factors may ease constipation, as will patient and carer education. Constipation can cause unnecessary anxiety and adjusting expectations to a less frequent bowel habit may help, as may gentle abdominal massage.

In the very unwell patient sitting on the toilet may become too uncomfortable. Occasionally a gentle planned manual evacuation may be the kindest way to manage the bowels.

4 Constipation in children is often multifactorial and requires several sessions with the parents and child before resolution can be expected. What is your approach to the use of laxatives and behavioural techniques in children in the acute situation and long term?

Most childhood constipation seems to be behavioural in origin. This situation has often become fraught with anxiety. The issue of toileting can easily become a battleground with the younger child.

We tend to toilet train by rewarding clean pants rather than production of stool, thereby encouraging retentive behaviour. Toilets can be very frightening for young children, with all sorts of fears about being flushed away.

Boys in particular learn to stand to urinate and seldom get the chance for opportunistic bowel emptying. An adult-sized seat with dangling feet can feel unsafe. If the stool becomes a little hard it can feel uncomfortable to pass, or even cause a minor painful fissure. The child then avoids defaecation, compounding the hard stool and discomfort.

Frantic morning routines, skipping breakfast, inadequate fibre and fluid intake, lack of permission to leave the classroom in response to the urge to defaecate and bullying in school toilets, or unappealing dirty toilets with broken locks, may contribute.

Sometimes simple education and adjustment of routines can resolve the problem. The whole family may need to get up 15 minutes earlier, eat a high-fibre breakfast and drink two cups of fluid. Private time should then be allowed in the toilet without the sense that there is a rush to leave the house. A school nurse may be able to arrange for teachers to allow unrestricted use of the toilet as needed.

It may be possible to manage the acute situation by a few doses of laxative and attention to the above factors to prevent recurrence. But once constipation has become an ingrained habit, especially if secondary soiling has become a feature, it is often necessary to give long-term oral stimulant laxatives (such as senna) or osmotic (such as magnesium salts) to break the pattern.

This will often be needed for six to 12 months. If impaction is allowed to persist, there is a risk that megarectum or megacolon will develop and if this continues at puberty it may be irreversible, often leading to misery throughout adult life.

Both parents and prescribers are often reluctant to agree to such laxative use, but there are really few alternatives other than the misery of continued soiling.A few children with neurological conditions will have physiological reasons for constipation and may need long-term laxatives or to learn bowel self-irrigation (used commonly in spina bifida).

5 I usually meet faecal impaction late in the day, just as the district nurses are leaving. They are usually happy to provide an enema the next day, but is there something I can do in the meantime?

Oral macrogols are licensed for relief of impaction. Up to eight sachets can be dissolved in a litre of water and drunk. However, many people prone to impaction find drinking this amount all at once difficult. It can also promote abdominal cramps and even faecal incontinence.

Alternatives are to wait until the morning (this is seldom an emergency situation). Or even consider giving an enema yourself if you already have the patient undressed and in the left lateral position for examination.

6 Faecal incontinence is most common in elderly people in nursing homes. I always try to ensure they are not constipated and that they are kept mobile. However, many have very lax anal sphincters. How should this group be managed?

Rectal loading with hard or soft stool is indeed the most common underlying mechanism of faecal incontinence in a care home population. Three-quarters of people in nursing homes are taking prescribed oral laxatives, many of them more than one.

Much of this prescribing tends to be on a routine rather than targeted basis and, as stated above, oral laxatives have an unpredictable timing of action. If the older person also has blunted anorectal sensation, sphincter laxity and/or diminished warning of the call to stool or a degree of confusion, coupled with immobility and dependence on summoning carers, faecal incontinence is a common result.

Additionally, there is a tendency to give medication regardless of bowel function and laxative-induced diarrhoea may result. Suppositories or micro-enemas tend to have a more predictable result than oral laxatives and can be given on an as-needed basis.

But education of staff will often be needed to ensure compliance. An assumption that older people do not like rectal preparations is often found to be untrue, although some confused individuals may not allow insertion.

7 I get lots of patients who say they are constipated, yet they have empty rectums. I also see many X-rays in which the colon is clearly loaded with faeces, yet the patient is not complaining. What is the relationship between symptoms and the finding of colonic loading?

The relationship between colonic and rectal contents and symptoms is far from straightforward. The rectum is seldom completely empty and the colon almost never is. A plain abdominal film is like taking an aerial photo of the M25: you can see that it is full of traffic but you cannot judge how fast it is moving. So although a film will detect severe loading, and fluid levels suggesting obstruction, it is not very useful for distinguishing milder forms of constipation from normal.

8 In intractable constipation, what investigations are helpful? Is there anything else in the management that might help?

An abdominal transit study – this involves ingesting radio-opaque markers over three days and then a plain abdominal X-ray on day six while off all laxatives. Normal transit should enable passage of 80 per cent or more of the markers. Retention of markers indicates slow transit.

A proctogram may be useful where incipient rectal prolapse or rectocele is suspected. Blood tests may reveal hypothyroidism or other metabolic disorders.Rectal irrigation is occasionally helpful, particularly in neurological patients.

9 How useful are physiotherapists and pelvic floor exercise in the management of constipation, especially in women?

Physiotherapists and nurses have developed programmes to teach women how to push without straining and evacuate effectively.

Many women with a lax pelvic floor or perineum can do exercises to strengthen this and learn how to support the perineum or a rectocoele. Positioning on the toilet and general muscle tone and fitness can also help.Biofeedback is a useful specialist adjunct when simple measures fail and there are several units around the country.

  • Christine Norton is professor of gastrointestinal nursing at King's College London, and a nurse consultant at St Mark's Hospital, Middlesex

Competing interests None declared

What I will do now

Dr Stott responds to the answers to his questions

I was interested to hear of the options to help investigate constipation, including a proctogram, and I will use blood tests more often to exclude hypothyroidism and other metabolic disorders.

But specifically:

• If patients use laxatives long term, I will encourage them to change preparation regularly to prevent therapy becoming ineffective

• If patients are to take opioids regularly, I will anticipate constipation and institute laxatives pre-emptively

• If patients are in the terminal phase of life, I will try to rectify potential causes of constipation such as immobility

• With children, I will spend more time discussing lifestyle issues

• I will be less wary of using mixed laxatives longer term in constipated children

• I will keep a phosphate enema and latex gloves in my bag for emergency use

Peter Stott is a GP in Tadworth, Surrey

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