Chapter 14 CHALLENGING CONSTIPATION

KEY POINTS

• Constipation is a symptom not a diagnosis.

• There are three subtypes of functional constipation (no structural or biochemical cause): slow transit constipation, pelvic floor dysfunction and normal tests (normal transit and normal pelvic floor function).

• Irritable bowel syndrome may present as normal transit constipation but abdominal pain is characteristic.

• A detailed history should include ruling out constipating drugs.

• New-onset constipation in older age is a red flag and colon cancer should be excluded.

• A careful digital rectal examination should be performed to identify the presence of obstruction or abnormal pelvic floor function, as well as looking for evidence of rectal cancer.

• A colonic transit study by radio-opaque markers or scintigraphy provides a good assessment of colonic transit time.

• The balloon expulsion test is usually abnormal in pelvic outlet obstruction.

• Biofeedback therapy is efficacious in treating pelvic outlet obstruction.

INTRODUCTION

Constipation is a symptom not a diagnosis. Patients mean different things when they complain of constipation, but it is often defined as two or more of the following for at least 3 months:

• Excessive straining to pass stool

• Hard or lumpy stools

• Stool frequency less than three times per week

• A sensation of incomplete evacuation

• Sensation of anorectal blockage

• Use of manual manoeuvres such as digital evacuation.

It is important to take a detailed history from a patient presenting with constipation and, in particular, to decide whether it is a new symptom or the first presentation of a long-term complaint. Investigations and treatment will be determined by these factors.

CONSTIPATION IN ADULTS

The prevalence of constipation in the general population has been reported to be as high as 20%. The symptom is more common in women and some report they become more constipated in the premenstrual week. Constipation is also common in pregnancy, during periods of immobilisation, following surgery and in the elderly. Women in particular report becoming constipated when they travel. Many women are reluctant to use public toilets or empty their bowels at work and this can further complicate treatment.

Constipation is rarely a presenting symptom of colon cancer. However, the possibility should be considered in each and every patient. Colon cancer is a common malignancy, affecting one in 18 men and one in 24 women. A consultation concerning bowel habit can be a good time to discuss screening for bowel cancer (e.g. by colonoscopy) even if the symptoms don’t warrant colonoscopy. Faecal occult blood testing is not an appropriate test for people with symptoms and should not be used to screen for bowel cancer in people who present with constipation.

There are a number of endocrine diseases that can present with constipation, including hypothyroidism and hypercalcaemia. Diabetes mellitus can also cause a change in bowel habit over time. Rarer conditions that can cause constipation include glucagon producing tumours, phaeochromocytoma and pseudohypoparathyroidism.

Constipation can also be associated with neurological disease, depression or anorexia nervosa. Very occasionally, a psychotic patient will complain that they haven’t emptied their bowel for an improbable length of time, such as a year or two. It is important to be vigilant for these rare psychological associations.

It is important to differentiate between two important disorders of colonic motility:

• Slow transit constipation—slower than normal movement of contents from the proximal to the distal colon and rectum

• Pelvic floor dysfunction (dyssynergic defecation or anismus)—the primary failure is an inability to evacuate adequately contents from the rectum.

Combination syndromes are possible whereby elements of slow transit and disorders of evacuation coexist. Other patients with no structural or biochemical explanation for their constipation may have normal transit and normal pelvic floor function. Some of these cases also have abdominal pain related to their constipation, and are classified as having irritable bowel syndrome (IBS); others do not have IBS or any other explanation.

ASSESSMENT

A thorough medical history and physical examination, including rectal examination, is required. Enquiries should be made about general health, diet, psychological status and any medications being taken.

History

A detailed history should include exactly what the patient means by constipation. How often, what shape and consistency is the motion and with what difficulty or ease does defecation occur? Is there any abdominal pain or bloating? Is there any rectal bleeding? It is also important to take a detailed laxative history: what laxatives are used, how often and the dosage. The dietary history should include:

• Is cereal eaten for breakfast and what type of cereal is it? (Some commercial cereals contain almost no fibre.)

• What sort of bread is consumed and how many pieces are eaten per day?

• How many pieces of fruit are eaten per day?

• How many servings of vegetables are eaten per day?

• How much water, juice or tea is consumed per day? Patients are often surprised to hear that a couple of short black coffees are not sufficient fluid intake.

• Ask about exercise.

Simple suggestions on dietary modification can make quite a deal of difference.

Ask the patient to keep a diet diary for a few days. Most people overestimate the amount of fibre and underestimate the amount of fat they consume.

Medications

Constipation is a common side effect of many medications, particularly in the elderly. These include:

• aluminium-based antacids

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