Constipation: managing the condition in adults

Constipation describes infrequency and difficulty when emptying the bowels. It can affect people of all ages, although it is more common in women; particularly those who are pregnant due to hormonal fluctuations. Older people — particularly those aged over 70 years — are also more likely to be affected by constipation because of several factors, including a more sedentary lifestyle, level of fluid intake, diet, and delaying the urge to defecate because of mobility issues.

For many people, constipation is transient in nature and easily treatable, but for others it can be a chronic condition causing substantial discomfort and pain^[1],[2]
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The prevalence of constipation in the UK is estimated at around 8.2% of the general population. However, the perception of constipation is widely variable, and 39% of men and 52% of women report straining when emptying their bowels in at least one in four occasions^[3]
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The incidence of constipation per year is five times higher in the elderly than in younger adults and is usually multifactorial since this population group is exposed to various risk factors for constipation, including medication (see Medicines known to cause constipation)^[4],[5]
. Reduced appetite in the elderly can lead to poor diet with a reduction in fibre intake and decreased fluid intake causing hard stools that are difficult to pass. Reduced mobility is also a common risk factor in the elderly since this reduces gut motility and contributes to constipation and faecal impaction^[5]
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Typical symptoms of constipation include abdominal pain, cramping, bloating, nausea and straining during bowel movements^[1],[2]
. Stools tend to be dry, hard and lumpy, and indicated as type 1 or 2 on the Bristol stool chart (also known as the Meyers scale)^[6]
. The pain and discomfort from chronic constipation and the associated complications can impact on a person’s quality of life, particularly in the elderly.

Chronic constipation can be classified as functional (or idiopathic) or secondary constipation^[1],[2]
. Functional constipation occurs without an anatomical or physiological known (e.g. because of poor diet). It is diagnosed by the exclusion of a pharmacological or medical cause.

Secondary constipation is caused by a drug or medical condition (see ‘Medicines known to cause constipation’). Conditions known to cause constipation include disorders that alter the functionality of the gastrointestinal tract, such as Crohn’s disease and ulcerative colitis. Less obvious conditions include multiple sclerosis, diabetes, hypothyroidism and Parkinson’s disease because of reduced mobility, weight gain, or reduced food and fluid intake. Conditions such as Parkinson’s disease and multiple sclerosis can also have direct effects on the nerves that control bowel function, leading to a weakness and uncoordinated contraction of pelvic floor and abdominal muscles and preventing the passage of stools.

Medicines known to cause constipation

Assessment

Constipation is usually diagnosed if a patient reports a reduced frequency of bowel movements, typically less than three bowel movements in one week^[4]
. This is not definitive, and the patient should also be asked about the frequency and character of any stools, and when constipation first presented. A physical or internal rectal examination may also be performed, which may confirm that faecal masses are palpable abdominally or perianally^[2]
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When assessing a patient for constipation, it is important to consider possible causes, such as medication and comorbidities. It is also important to check for red flag symptoms such as unexplained weight loss, rectal bleeding, a family history of colon cancer or inflammatory bowel disease, or signs of obstruction^[2]
. Patients with any red flag symptoms should be referred to a specialist for further investigation.

The Rome III diagnostic criteria can be used to classify functional gastrointestinal disorders, and may be useful when functional constipation is suspected and contributing medicines or medical conditions have been excluded^[9]
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Using the Rome III diagnostic criteria, constipation may be diagnosed if patients who do not take laxatives report at least two of the following in any three-month period during the previous six months:

• Straining in at least 25% of bowel motions;
• Lumpy or hard stools in at least 25% of bowel motions;
• Sensation of incomplete evacuation in at least 25% of bowel motions;
• Sensation of anorectal blockage in at least 25% of bowel motions;
• Manual manoeuvres have been required to facilitate at least 25% of bowel motions (e.g. digital evacuation);
• Fewer than three bowel movements per week;
• Loose stools are not present, and there are insufficient criteria for irritable bowel syndrome^[9]
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Treatment

It is important to consider the primary cause when treating constipation. In many cases, constipation may be a result of poor diet and lack of exercise, and therefore patients should be encouraged to increase the fibre in their diet and fluid intake before trying laxatives.

Fibre increases the bulk and plasticity of stools, which in turn promotes propulsive activity and movement through the colon, thus preventing constipation^[3]
. Good sources of fibre can come from pulses, such as beans, chickpeas and lentils, as well as wholegrain bread, rice and pasta, nuts and dried fruit. Typically, patients should be warned to avoid caffeine containing products since they can contribute to constipation through dehydration. Low-fibre or high-fat foods, such as dairy products and eggs, can slow down digestion and therefore cause constipation.

There is little evidence that exercise can also increase gut motility. However, one study found that women who reported physical activity of once a week or more were significantly less likely to report constipation^[10]
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Although improved diet and exercise may relieve acute constipation, many patients require pharmacological treatment. In 2010, the then-NHS Information Centre (now the Health & Social Care Information Centre) reported that 15.9 million prescriptions were dispensed in the community in England for laxatives, at a cost of £70.6m^[11]
; this did not include laxatives purchased over the counter. The UK National Institute for Health and Care Excellence (NICE) has recommended that clinicians review the prescribing of laxatives for adults and ensure they are limited to the short‑term treatment of constipation in circumstances when dietary and lifestyle measures have proven unsuccessful or if there is an immediate clinical need^[12]
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There are many different classes of laxatives with differing modes of action; as such, a combination of laxatives is usually employed to maximise efficacy.

Stimulant laxatives (e.g. senna, bisacodyl) improve intestinal motility via muscle contractions and reduce water loss from the faeces, softening the stool. A potential side effect of stimulant laxatives is abdominal cramping (caused by the increased intestinal motility).

Faecal softeners (e.g. docusate) stimulate peristalsis by increasing faecal mass; they act to lower surface tension and allow water and fats to penetrate hard, dry faeces.

Co-danthromer and co-danthrusate are combination products containing the stimulant laxative dantron and a stool softening agent (poloxamer ‘188’ and docusate, respectively). Dantron-containing products must only be used in terminally ill patients because it may be carcinogenic^[13]
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Bulk-forming laxatives (e.g. ispaghula husk, methylcellulose) treat constipation by increasing faecal mass through water binding to stimulate peristalsis^[13]
. This class of laxatives usually takes a couple of days to achieve full effect.

Osmotic laxatives (e.g. macrogols, lactulose) increase the amount of water in the large bowel, either by drawing fluid from elsewhere in the body or retaining the fluid consumed with the medicine^[13]
. Patients may feel dehydrated when using this class of laxatives; this can be avoided by drinking fluids when taking the laxative.

Enemas are another option for the treatment of constipation, particularly for patients unable to take oral laxatives. Enemas containing arachis oil (ground-nut oil, peanut oil) lubricate and soften impacted faeces to encourage a bowel movement, although they are contraindicated in patients with nut allergies. Phosphate enemas and sodium citrate enemas are also used when bowel clearance is required rapidly (e.g. before radiology, endoscopy or surgery).

Prucalopride was licensed by the European Medicines Agency in 2009 as a treatment option for women in whom laxatives fail to provide adequate relief^[14]
. Prucalopride is a selective serotonin 5-HT₄ receptor agonist that stimulates colonic motility and accelerates gastric emptying^[15]
. The efficacy and safety profile of the medicine has not been investigated fully in men, and therefore its licence is limited to women. It is contraindicated in patients with intestinal perforation or obstruction, and those with severe inflammatory bowel conditions including Crohn’s disease and ulcerative colitis^[15]
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Lubiprostone is a novel medicine licensed for the treatment of chronic idiopathic constipation as a two-week treatment course; alternative treatment should be sought if there is no response after two weeks. Studies have found lubiprostone to be well tolerated in up to a year of treatment^[16]
. Its mechanism of action involves the activation of chloride channels, increasing intestinal fluid secretion and thus facilitating intestinal motility^[17]
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Complications

Faecal impaction can occur in patients with untreated constipation. This is when dried, hard stools collect in the rectum, causing an obstruction and making it difficult for stools to pass naturally. The accumulation of stools unable to pass increases the pressure against the muscles in the rectum, causing them to weaken^[1],[10]
. This reduction in muscle tone can lead to overflow incontinence, where watery stools leak around the impacted hard stools.

Faecal impaction is painful and can be distressing for patients, who may remain housebound because of the fear of incontinence in public areas. It is very unlikely for patients to pass the stools naturally if impacted; treatment usually starts with a high dose osmotic laxative. If inadequate response is achieved through oral laxatives, a bisacodyl suppository or sodium citrate enema can be used (see below for case study regarding faecal impaction). It could take several months for colorectal tone to be restored and some patients are given exercises to help accelerate the healing process.

Haemorrhoids are areas of swelling containing enlarged blood vessels around the anus, caused by increased pressure in the blood vessels as a result of straining while defecating. Haemorrhoids can cause bleeding after the passing of stools and can be itchy; they are usually relatively simple to treat with a short course of topical product containing corticosteroids and a local anaesthetic^[13]
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In severe cases, laser therapy or banding ligation may be used. Banding ligation involves tying elastic bands tightly around each haemorrhoid, restricting the blood supply and causing them to detach^[12]
. Surgery may be required to remove haemorrhoids if these treatments are ineffective.

Rectal prolapse is a more serious complication of repeated straining during bowel movements, which involves a protrusion of the lower intestine through the anus. This is treated surgically^[1]
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Anal fissures are a possible complication of constipation, where the forced passage of hard stools causes small tears through the lining of the anal canal. Patients experience a burning pain and may notice bleeding following bowel motions. Anal fissures are usually self-limiting and heal without the need for medical intervention. However, topical glyceryl trinitrate ointment can relieve the associated pain by the release of nitric oxide, which mediates the relaxation of the internal anal sphincter, thus reducing anal pressure and improving blood flow.

Alternatively, a topical anaesthetic such as lidocaine can be applied before a bowel motion. Once healed, patients may be required to take laxatives or increase their dietary fibre intake to prevent recurrence^[13]
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