AKT · Gastroenterology/Colon & rectumlow yield

Constipation

Infrequent/difficult defecation (primary/functional or secondary)

Overview

Infrequent, difficult or incomplete defecation with hard stools. Mostly primary/functional (low fibre/fluid, inactivity, ignoring urge), but secondary causes matter: drugs (opioids, iron, anticholinergics, calcium-channel blockers), metabolic (hypothyroidism, hypercalcaemia), neurological, obstruction (cancer), and in children stool-withholding. Managed with lifestyle + a stepped laxative approach; red flags need investigation.

Recognise

Infrequent (<3/week), hard, lumpy stools; straining, incomplete evacuation, abdominal discomfort/bloating
Secondary clues: opioids/iron/CCBs (drugs), cold intolerance/weight gain (hypothyroid), polyuria/bones-stones (hypercalcaemia), red flags (cancer)
Complications: faecal impaction with overflow diarrhoea, haemorrhoids/fissures, urinary retention

Red flags

NEW change in bowel habit, rectal bleeding, weight loss, anaemia, abdominal/rectal mass, age ≥50 → investigate for colorectal cancer
Faecal impaction with overflow; obstruction

Differentials & how to tell them apart

Colorectal cancernew change in habit + bleeding/weight loss/anaemia in older patients — 2-week-wait

Hypothyroidism / hypercalcaemiametabolic causes — check TFTs/calcium

Obstructionabsolute constipation + distension/vomiting — surgical

IBS-Cpain related to defecation, no red flags

Investigations

Clinical; review drugs and screen for secondary causes (TFTs, calcium) where suggested; investigate red flags (colonoscopy). Abdominal exam/PR; AXR for impaction.

Management

Lifestyle + stepped laxatives (bulk → osmotic → stimulant); treat secondary causes

1Lifestyle measures and review constipating drugs. Stepped laxatives: bulk-forming, then osmotic (macrogol), then add a stimulant. Disimpaction (high-dose macrogol) for faecal loading with overflow.Gate: Exclude RED FLAGS (new change in habit, bleeding, weight loss, anaemia, mass, age ≥50) → colorectal cancer pathway; and SECONDARY causes (hypothyroidism, hypercalcaemia, drugs) before treating as simple functional constipation
2Refractory → prucalopride/linaclotide; opioid-induced → naloxegol; treat the underlying cause; biofeedback for evacuation disorders.

Lifestyle (fibre, fluids, activity, toileting) — first-line

Bulk-forming laxative (ispaghula) → osmotic (macrogol/lactulose) → stimulant (senna) — stepped approach; macrogol for impaction/opioid-induced

Review/stop constipating drugs; treat the cause — opioids, iron, anticholinergics; naloxegol for opioid-induced

Key points

Mostly functional — lifestyle + stepped laxatives. But a NEW change in habit (esp. with bleeding/weight loss/anaemia) is cancer until excluded, and drugs/hypothyroidism/hypercalcaemia are the secondary causes to screen.

Monitor & prognosis

Bowel habit; red-flag review.

Good with management.

Source: NICE CKS Constipation