Constipation is a symptom and not a disease and can be caused by many different factors (Table 14.1) but the overwhelming majority of cases in non-elderly patients will be due to lack of dietary fibre. To aid diagnosis, questions need to be asked about the frequency and consistency of stools, nausea, vomiting, abdominal pain, distension, discomfort, mobility, diet and other concurrent symptoms or disorders the patient may be experiencing. It may also be necessary to ask about access to a toilet or commode. The individual with limited mobility may suppress the urge to defaecate because of difficulty in getting to the toilet. Likewise, lack of privacy or dependency on a nurse or carer for toileting may result in urge suppression that precipitates constipation or exacerbates an underlying predisposition. Patients with unexplained constipation of recent onset or a sudden aggravation of existing constipation associated with abdominal pain and the passage of blood or mucus, and long-standing constipation unresponsive to treatment require further investigation. Investigations include sigmoidoscopy/colonoscopy, barium enema, full blood count and biochemical monitoring including thyroid function tests (Fig. 14.2).

Table 14.1 Causes of constipation

Cause	Comment
Poor diet	Diets high in animal fats, for example, meats, dairy products, eggs, and refined sugar, for example, sweets, but low in fibre predispose to constipation
Irritable bowel syndrome	Spasm of colon delays transit of intestinal contents. Patients have a history of alternating constipation and diarrhoea
Poor bowel habit	Ignoring and suppressing the urge to have a bowel movement will contribute to constipation
Laxative abuse	Habitual consumption of laxatives necessitates increase in dose over time until intestine becomes atonic and unable to function without laxative stimulation
Travel	Changes in lifestyle, daily routine, diet and drinking water may all contribute to constipation
Hormone disturbances	For example, hypothyroidism, diabetes. Other clinical signs should be more prominent, for example, lethargy and cold intolerance in hypothyroidism and increased urination and thirst in diabetes
Pregnancy	Mechanical pressure of womb on intestine and hormonal changes, for example, high levels of progesterone
Fissures and haemorrhoids	Painful disorders of the anus often lead patients to suppress defaecation, leading to constipation
Diseases	Many disease states may have constipation as a symptom, for example, scleroderma, lupus, multiple sclerosis, depression, Parkinson’s disease, stroke
Mechanical compression	Scarring, inflammation around diverticula and tumours can produce mechanical compression of intestine
Nerve damage	Spinal cord injuries and tumours pressing on the spinal cord affect nerves that lead to intestine
Colonic motility disorders	Peristaltic activity of intestine may be ineffective, resulting in colonic inertia
Medication	See Table 14.2
Dehydration	Insufficient fluid intake or excessive fluid loss. Water and other fluids add bulk to stools, making bowel movements soft and easier to pass
Immobility	Prolonged bedrest after an accident, during an illness or general lack of exercise
Electrolyte abnormalities	Hypercalcaemia, hypokalaemia

Fig. 14.2 A diagnostic algorithm for constipation.

General management

In uncomplicated constipation, education and advice on diet and exercise are the mainstays of management and may adequately control symptoms in many individuals. Typically this advice will include reassurance that the individual does not have cancer, that the normal frequency of defaecation varies widely between individuals, and that mild constipation is not in itself harmful.

If the patient is taking medication for a concurrent disorder this must be assessed for its propensity to cause constipation. In the UK, over 700 medicinal products, including ophthalmic preparations, have constipation listed as a possible side effect. Common examples of medicines involved are presented in Table 14.2.

Table 14.2 Examples of medicines known to cause constipation (frequency defined as very common [>10%] or common [1–10%])

α-Blocker	Prazosin
Antacid	Aluminium and calcium salts
Anticholinergic	Trihexyphenidyl, hyoscine, oxybutynin, procyclidine, tolterodine
Antidepressant	Tricyclics, SSRIs, reboxetine, venlafaxine, duloxetine, mirtazepine
Antiemetic	Palonosetron, dolasetron, aprepitant
Antiepileptic	Carbamazepine, oxcarbazepine
Antipsychotic	Phenothiazines, haloperidol, pimozide and atypical antipsychotics such as amisulpride, aripiprazole, olanzapine, quetiapine, risperidone, zotepine, clozapine
Antiviral	Foscarnet
β-Blocker	Oxprenolol, bisoprolol, nebivolol; other β-blockers cause constipation more rarely
Bisphosphonate	Alendronic acid
CNS stimulant	Atomoxetine
Calcium channel blocker	Diltiazem, verapamil
Cytotoxic	Bortezomib, buserelin, cladribine, docetaxel, doxorubicin, exemestane, gemcitabine, irinotecan, mitozantrone, pentostatin, temozolomide, topotecan, vinblastine, vincristine, vindesine, vinorelbine
Dopaminergic	Amantadine, bromocriptine, carbegolide, entacapone, tolcapone, levodopa, pergolide, pramipexole, quinagolide
Growth hormone antagonist	Pegvisomant
Immunosuppressant	Basiliximab, mycophenolate, tacrolimus
Lipid-lowering agent	Colestyramine, colestipol, rosuvastatin, atorvastatin (other statins uncommon) gemfibrozil
Iron	Ferrous sulphate
Metabolic disorder	Miglustat
Muscle relaxant	Baclofen
NSAID	Meloxicam; other NSAIDs, for example, aceclofenac, and COX-2 inhibitors reported as uncommon
Smoking cessation	Bupropion
Opioid analgesic	All opioid analgesics and derivatives
Ulcer healing	All proton pump inhibitors, sucralfate

Non-drug treatment

Non-drug treatment is advocated as first-line therapy for all patient groups, except those who are terminally ill. This often includes advising an increase in fluid intake at the same time as reducing strong or excessive intake of tea or coffee, since these act as a diuretic and serve to make constipation worse.It is generally recommended that fibre intake in the form of fruit, vegetables, cereals, grain foods, wholemeal bread, etc. be increased to about 30 g/day. The amounts of fibre in commonly eaten foods have been published (MeReC, 2004). Such a diet should be tried for at least 1 month to determine if it has an effect. Most will notice an effect within 3–5 days. Unfortunately, a high-fibre diet is not without problems, with patients complaining of flatulence, bloating and distension, although these effects should diminish over a period of several months. Patients who increase their fibre intake must also be advised to drink 2 L of water a day. Where an intake of this volume cannot be ingested it will be necessary to avoid increasing dietary fibre. An increased level of exercise should also accompany the raised fibre intake as this is thought to help relax and contract the abdominal muscles and help food move more efficiently through the gut.

A high-fibre diet is not recommended in those with megacolon or hypotonic colon/rectum because they do not respond to bulk in the colon. Similarly, a high-fibre diet may not be appropriate in those with opioid-induced constipation.

Drug treatment

Drug treatment is indicated where there is faecal impaction, constipation associated with illness, surgery, pregnancy, poor diet, where the constipation is drug induced, where bowel strain is undesirable, and as part of bowel preparation for surgery. The various laxatives available can be classified as bulk forming, stimulant, osmotic and faecal softeners. A systematic review (Tramonte et al., 1997) identified 36 trials involving 1815 participants that met their inclusion criteria. Twenty of the trials compared laxative against placebo or regular diet, 13 of which demonstrated statistically significant increases in bowel movement. The remaining 16 trials compared different types of laxatives with each other. The review concluded that laxative use was superior to placebo but due to a lack of comparative data could not conclude which laxative group was most efficacious. Further, more recent reviews have found good evidence that macrogols are effective, as are ispaghula husk and bisacodyl, although data is still lacking on which laxative is best (Frizelle and Barclay, 2007).

In general, the fit, active, elderly person should be treated as a younger adult. In contrast, management of constipation in children is often complex. Early treatment is required in children to avoid developing a megarectum, faecal impaction and overflow incontinence. Encouraging the child to use the toilet after meals and increasing dietary fibre have a role alongside oral drug treatment. Depending on circumstances, behavioural therapy may be indicated. In pregnancy, if drug treatment is required, bulk-forming laxatives are first choice, but if stools remain hard then either changing to or adding in lactulose or a macrogol is advocated. Conversely, if stools are soft but the woman still finds difficulty in passing stools then a stimulant laxative should be considered.