Challenging constipation

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Chapter 14 CHALLENGING CONSTIPATION

• 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.

Physical examination

Every patient requires a thorough physical examination, including rectal examination, and neurological examination to exclude systemic illnesses that may cause constipation. The abdomen should be examined for masses. The thyroid status of the patient should be assessed.

Physical examination includes a check for perianal disease that might be complicating the constipation, such as haemorrhoids or anal fissures. People who consistently strain at stool are more likely to have haemorrhoids. If the haemorrhoids require banding, it is particularly important to alter the underlying bowel habit so that haemorrhoids don’t recur. An anal fissure is not always preceded by constipation. However, once the fissure is present, anal spasm can make defecation very painful and difficult. The constipation in this situation may be difficult to treat until the fissure has been dealt with. Anorectal examination may also reveal skin tags and skin excoriation.

A careful digital rectal examination should be performed to exclude a rectal stricture or blood in the stool. During the rectal examination, the patient should be asked to bear down as if to defecate and the examiner should perceive relaxation of the external anal sphincter together with perineal descent. One should suspect dyssynergic defecation if this response is absent.

Some patients, particularly women, are troubled by rectal prolapse associated with long-term straining at stool. This is a symptom that is often not volunteered and direct enquiry and physical examination are required. Many women who have a degree of rectal prolapse will continue to strain at defecation because the sensation caused by the prolapse leads to the belief that there are still faeces in the rectum. A discussion of the mechanics of defecation with the aid of a diagram can be very helpful. Mucosal resection is indicated in some cases. Behaviour therapy, incorporating biofeedback, has a role in some long-term cases.

Neurological examination should screen for Parkinson’s disease, multiple sclerosis, stroke, spinal cord injury or myotonic dystrophy. Look at the skin. Some people with scleroderma can have severe constipation whereas others are troubled by diarrhoea due to bacterial overgrowth in the small intestine. Appropriate management of these conditions is required as well as assessment and management of the constipation.

Investigations

Baseline investigations to exclude systemic diseases should be done initially. These include serum calcium, glucose and thyroid function tests.

A plain abdominal X-ray can be very helpful if there is doubt about the degree of constipation. Some patients will have marked faecal loading. Structural evaluation of the colon is appropriate and is done by carrying out a colonoscopy, or flexible sigmoidoscopy and barium enema. Colonoscopy is indicated if there has been a recent change in bowel habit or rectal bleeding. It may also be advisable if there is a family history of bowel cancer.

Further investigations

Colonic transit study (transit time)

Indicates the time for stool movement through the colon. The radio-opaque marker study may show one of three patterns: normal; slow transit; hold-up in the sigmoid and rectum suggesting, but not establishing, an obstructive defecation pattern.

In some patients with constipation, the colon transit time may be normal. In this scenario, it is important to exclude pelvic floor dysfunction. Similarly, if transit is slow this may be due to pelvic floor dysfunction, not colonic disease.

Balloon expulsion test

Provides an assessment of the patient’s ability to expel a water filled balloon. Most patients can expel the device within one minute. If the patient is unable to expel the balloon within 3 minutes, the clinician should suspect dyssynergic defecation.

FIGURE 14.1 Algorithm for diagnosis and management of constipation.

Anorectal manometry

Can confirm pelvic floor dysfunction, typically with absence or insufficient relaxation of the external sphincter pressure on straining, or poor propulsion, or both. Obstructed defecation may be associated with excessive straining, trouble letting go and a feeling of incomplete emptying. Patients may sit in a very peculiar position to try and empty the rectum. Some patients report splinting the perineum or even performing manual evacuations on themselves.

Hirschsprung’s disease (congenital megacolon) is rare but presents with chronic constipation. During anorectal manometry, the anorectal inhibitory reflex is tested; failure of normal internal anal sphincter relaxation with distention suggests Hirschsprung’s disease. Rectal biopsy looking for absence of ganglion cells is diagnostic.

Defecography

Provides useful information about anatomical and functional changes in the anorectum. An alternative is MRI defecography. Such testing should be considered if anorectal manometry is equivocal or an anatomical obstruction (e.g. large rectocele) is suspected.

TREATMENT

It is rare for there to be a ‘quick fix’ in the treatment of chronic constipation. Many people benefit from a bowel program consisting of an improved diet, increased fluid intake and daily exercise. Others may require fibre supplementation or medications (Table 14.1). It is important to emphasise to some patients that they must take responsibility for their improvement by making time to go to the toilet in the morning or answering the call to stool when it comes without straining excessively.

TABLE 14.1 Drugs used to treat chronic constipation

Type of drug	Example
Bulking or hydrophilic laxatives	Psyllium (ispaghula), methylcellulose, bran, plantain derivatives, Aloe vera
Surfactant or softening or wetting agents	Docusate, poloxalkol
Osmotic laxatives	Sorbital, lactulose, milk of magnesia (magnesium hydroxide), polyethylene glycol (PEG) solutions
Peristaltic stimulants	Senna, bisacodyl, cascara
Prokinetics	Tegaserod
Chloride channel activator	Lubiprostone

Diet

Many people have insufficient fibre in their diet. Ideally, adults should consume about 30 g of fibre per day. Fibre should be increased gradually to avoid initial bloating and discomfort. It is important to give patients information as to what constitutes a high-fibre diet rather than just a figure of the amount of grams that need to be consumed. Pocket-sized books with information on the fat and fibre content of almost any food are widely available. It is useful to suggest a patient keep a diet diary in order to calculate their fibre intake over a couple of weeks.

Some people who do not respond to an increased dietary fibre intake still have benefit from adding psyllium to the diet. Adequate fluid intake is important to avoid dehydration, but increased fluids otherwise probably help very little. Exclude an eating disorder; anorexia nervosa will induce constipation because of inadequate dietary intake.

Laxatives

If fibre supplements have been unsuccessful it may be appropriate to try a regular laxative. Generally it is advisable to discover the lowest effective regular dose to control the patient’s constipation. This is a matter of trial and error. Many constipated people will need laxatives for the rest of their lives and there is no clear evidence that this makes constipation worse over time. However, many clinicians avoid prescribing regular bowel stimulants such as senna or bisacodyl. Epsom salts are a cheap effective osmotic laxative for many people. The bitter taste can be masked by lemon juice. Sorbitol and lactulose are osmotic laxatives with a very sweet taste. However, they are relatively expensive. Polyethylene glycol is useful for more severe cases and can be taken regularly.

It is useful to give the patient an information sheet about constipation to take home, stressing that it is normal to empty the bowel between three times a day and three times a week, and making clear suggestions about what forms of therapy can be tried for that specific individual and how long they should persevere before asking for further clarification or help. A ‘step-up’ approach works well for many patients. For instance, a simple fibre supplement such as psyllium should be tried for a couple of weeks. If unsuccessful, the dose can be slowly increased or another fibre supplement such as sterculia should be tried for a couple of weeks. If unsuccessful, an osmotic laxative can be suggested. People who have difficulty with evacuation may benefit from glycerine suppositories or a faecal softener. If the constipation has been a very long-term problem, it is worthwhile asking the patient to come back for further evaluation and advice.

Other therapies

Lubiprostone is a bicyclic fatty acid that stimulates chloride channels in the intestines, increasing fluid secretion. It has been shown to be superior to placebo in the treatment of chronic constipation. Nausea is a common side effect.

Tegaserod is a 5-HT₄ agonist that has efficacy in treating constipation-predominant irritable bowel syndrome in women and chronic constipation in men and women under age 65. Side effects include diarrhoea and headache.

Patients with obstructed defecation may benefit from biofeedback techniques. The purpose of biofeedback therapy is to restore a normal pattern of defecation by using an instrument-based education program. The primary goals are twofold: to correct the underlying dyssynergia that affects the puborectalis and anal sphincter muscles, and to improve rectal sensory perception. Symptomatic improvement using this technique has been reported in approximately 70% of patients.

In patients with confirmed severe slow transit constipation, a colectomy and ileorectal anastomosis may be considered; localised colonic resections are not helpful. In this case, it is essential to exclude pelvic floor dysfunction and a more widespread motility disorder (e.g. small intestinal pseudo-obstruction) with appropriate testing at a specialised centre. Those patients with true colonic inertia typically have loss of the interstitial cells of Cajal, the pacemaker cells of the colon. A megacolon may develop, but is rare.

SUMMARY

Constipation is a very common problem with a wide spectrum of symptoms including excessive straining, hard stools, feeling of incomplete evacuation, use of digital manoeuvres, or infrequent defecation. An appropriate history and physical examination is required to be sure that the symptom of constipation is not the manifestation of some more serious underlying condition. Functional constipation consists of two major subtypes: slow transit constipation and pelvic floor dysfunction. Patients with irritable bowel syndrome have pain, and may exhibit features of both types of constipation. The condition can be managed in the vast majority of cases with simple advice on diet and lifestyle. Biofeedback therapy is an important advance for patients with dyssynergia.

FURTHER READING

American Gastroenterological Association medical position statement: guidelines on constipation. Gastroenterology. 2000;119:1761-1778.

Bharucha A, Wald A, Enck P, et al. Functional anorectal disorders. Gastroenterology. 2006;130(5):1510-1518.

Brandt L, Prather CM, Quigley EM, et al. Systematic review on the management of chronic constipation in North America. Am J Gastroenterol. 2005;100(Suppl 1):S5-S21.

Wald A. Chronic constipation: advances in management. Neurogastroenterol Motil. 2007;9:4-10.

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