Constipation

Constipation is a common gastrointestinal symptom characterised by infrequent bowel movements, difficulty passing stool, or a sense of incomplete evacuation.

It is one of the commonest presenting complaints across all age groups, particularly in older adults. In this group it contributes directly to functional incontinence, urinary retention and, in severe cases, faecal impaction with overflow diarrhoea.

Causes range from simple functional constipation to constipation secondary to a structural, metabolic or neurological condition. Functional constipation is the commonest presentation. It reflects a combination of dietary, behavioural and, in older adults, medication related factors.

Careful clinical assessment identifies the small but important proportion of presentations needing further investigation.

Classification and pathophysiology

• Functional (primary) constipation is the commonest presentation. It reflects inadequate dietary fibre and fluid intake, insufficient physical activity, and frequently habitual suppression of the normal defecatory urge (given inconvenient timing or environment).
• In a subset of patients there is a specific disorder of colonic transit (slow transit constipation).
• In another subset there is a disorder of the coordinated pelvic floor and anal sphincter relaxation needed for normal defecation (dyssynergic defecation, also termed pelvic floor dyssynergia). This subtype is important and frequently underrecognised, and needs targeted diagnostic assessment and treatment.
• Secondary constipation reflects an identifiable underlying cause.
• Medication effects: opioids are a particularly important, common and predictable cause. Others include anticholinergic medications, calcium channel blockers and iron supplementation, among numerous agents.
• Metabolic and endocrine causes: hypothyroidism and hypercalcaemia.
• Neurological causes: Parkinson disease, multiple sclerosis and spinal cord pathology, which disrupt the neurological control of colonic motility and defecation.
• Structural causes include colorectal malignancy, the single most important diagnosis to consider and exclude, particularly in older patients or those with red flag features.
• Constipation in older adults reflects the general risk factors plus age related changes in colonic motility, reduced mobility and physical activity, and inadequate dietary and fluid intake. Dental or swallowing difficulty can limit fibre intake further.
• The cumulative burden of constipating medications in polypharmacy is frequently substantial.
• In older adults constipation has additional significance. It contributes directly to delirium and functional incontinence. In severe cases faecal impaction can cause serious complications including bowel obstruction or, rarely, stercoral perforation.

• Reduced stool frequency (generally fewer than three bowel movements per week, though normal frequency varies considerably between individuals) is typical.
• Other typical features: straining with defecation, passage of hard or lumpy stool, a sensation of incomplete evacuation, and in some patients a sensation of anorectal obstruction or blockage. In more severe cases manual manoeuvres are needed to facilitate defecation. The Rome diagnostic criteria for functional constipation incorporate these features.
• Abdominal discomfort and bloating may accompany the core bowel symptoms. In more severe or longstanding cases there may be nausea and reduced appetite.
• With faecal impaction, overflow diarrhoea may paradoxically occur: liquid stool leaking around an impacted, obstructing faecal mass. This can be diagnostically confusing, particularly in older, frail patients. It should prompt active consideration of impaction rather than management as straightforward diarrhoea.
• Red flag features warrant further investigation to exclude an underlying structural or other serious cause.
• Red flags are new onset constipation in an older patient without a clear precipitant, unintentional weight loss, rectal bleeding, iron deficiency anaemia, a palpable abdominal or rectal mass, and a family history of colorectal cancer or inflammatory bowel disease.
• Any of these features warrants prompt investigation rather than symptomatic management alone.
• Dyssynergic defecation presents with significant, disproportionate straining and a sense of anorectal blockage, though the stool is not necessarily hard.
• There is often a history of prolonged, excessive time spent attempting defecation. Some patients rely on manual manoeuvres (including digital rectal or vaginal pressure) to pass stool.
• Recognise this pattern, because it implies a distinct mechanism with its own targeted treatment.

• The essential foundation of diagnosis is a full clinical history. Ask about stool frequency, consistency and associated symptoms, review medication thoroughly, and screen for red flag features.
• Straightforward functional constipation is generally diagnosed clinically, without extensive investigation in the absence of red flag features.
• Digital rectal examination is an essential, simple component of assessment. It evaluates faecal impaction, a palpable rectal mass and anal sphincter tone.
• Where dyssynergic defecation is suspected, digital examination also assesses the coordination of pelvic floor and sphincter relaxation during a simulated straining manoeuvre.
• Blood tests (full blood count, thyroid function, calcium) are appropriate for new onset or significant constipation, particularly in older patients, to identify a metabolic or endocrine contributing cause.
• Colonoscopy or, where more appropriate to the clinical context, computed tomography colonography is indicated where red flag features are present. Excluding colorectal malignancy is essential in appropriately selected, higher risk patients.
• Where functional constipation does not respond adequately to standard first line management, further testing is appropriate. This applies particularly where dyssynergic defecation is suspected from the clinical pattern.
• Anorectal manometry and, where available, balloon expulsion testing give objective assessment of anorectal sphincter function and coordination. They confirm dyssynergic defecation and guide targeted biofeedback treatment.
• Colonic transit studies support assessment and confirmation of slow transit constipation where this subtype is suspected.

• General, first line measures: optimise dietary fibre intake, ensure adequate fluid intake, encourage regular physical activity, and establish a regular toileting routine.
• Increase fibre gradually, because a rapid increase can worsen bloating, particularly where colonic transit is significantly slowed.
• Capitalise on the physiological gastrocolic reflex by attempting defecation after meals. Respond to the normal defecatory urge rather than habitually suppressing it.
• Bulk-forming laxatives (including ispaghula husk) are a reasonable first line option for mild constipation. They increase stool bulk and water content, and need adequate concurrent fluid intake to be effective.
• Bulk-forming laxatives are generally less suitable, and potentially counterproductive, in significant slow transit constipation or dyssynergic defecation. They may worsen bloating and discomfort without addressing the underlying mechanism.
• Osmotic laxatives work by drawing water into the bowel lumen, softening stool and facilitating passage. They are standard, effective treatment for the great majority of patients with functional constipation.
• Macrogol preparations are generally well tolerated, effective and widely used as first line or early treatment. Lactulose is an alternative, though generally associated with greater bloating because colonic bacteria ferment it.
• Stimulant laxatives (senna, bisacodyl) act by direct stimulation of colonic motility. They are an effective option, particularly for more refractory constipation or as an adjunct to osmotic laxatives. Inappropriate, chronic or excessive use raises separate considerations (see laxative abuse).
• Newer agents are effective for chronic constipation not adequately responding to conventional laxatives.
• Prucalopride is a selective serotonin receptor agonist that promotes colonic motility.
• Linaclotide is a guanylate cyclase-C agonist with both prosecretory and direct visceral analgesic effects. It is particularly relevant where significant abdominal pain or discomfort accompanies the constipation.
• Dyssynergic defecation is managed with biofeedback therapy. This is a structured programme using real-time visual or auditory feedback to retrain correct, coordinated relaxation of the pelvic floor and anal sphincter musculature during attempted defecation.
• Biofeedback is the evidence based, generally highly effective treatment for this subtype. Standard laxative treatment alone is generally inadequate, because the problem is one of functional coordination.
• Faecal impaction needs initial disimpaction. Typically use a high dose osmotic laxative regimen, following an established, structured disimpaction protocol.
• Where oral treatment is inadequate or not tolerated, use rectal treatment (suppository or enema). Reserve digital rectal removal of impacted stool for cases where these measures fail.
• Follow disimpaction with a regular, structured maintenance laxative regimen to prevent recurrence. Recurrence risk is substantial and well recognised, particularly in older, frail patients with ongoing risk factors.
• Manage any identified underlying or contributing secondary cause. Review and, where clinically feasible, modify any constipating medication. Treat any metabolic, endocrine or structural cause.
• Review treatment response regularly. Attend proactively to bowel function as a routine part of care in higher risk populations: older adults, those on opioid medication, and those with neurological conditions.
• Opioid induced constipation is predictable and essentially universal, so prescribe a laxative concurrently rather than reactively once symptoms develop.
• This extremely common condition is frequently underappreciated in its clinical significance and impact.