Red flags
- New change in bowel habit >50yo without prior workup -> exclude malignancy
- PR bleeding, unintentional weight loss, iron deficiency anaemia
- Faecal impaction with overflow incontinence ("spurious diarrhoea") - easily mistaken for diarrhoea
- Signs of obstruction - distension, vomiting, absolute constipation
- Acute severe abdominal pain -> volvulus, obstruction
Differential by mechanism
- Slow transit, normal transit with disordered evacuation, pelvic floor dyssynergia
- Drugs - opioids, anticholinergics, CCBs, iron, calcium supplements, antipsychotics
- Metabolic - hypothyroidism, hypercalcaemia, hypokalaemia, diabetes
- Neurological - Parkinson's, spinal cord lesion, autonomic neuropathy
- Structural - colorectal malignancy, stricture, rectal prolapse, anal fissure (pain-avoidance)
- Immobility + low fibre/fluid intake - very common contributor in frail elderly
- Cognitive/behavioural - dementia (forgets urge), depression
Focused history
- Bowel habit baseline vs current, stool form (Bristol chart), frequency
- Straining, incomplete evacuation, need for digital assistance
- Diet, fluid intake, mobility level
- Full medication review - anticholinergic burden, opioids
- PR bleeding, weight loss, family history of colorectal cancer
- Overflow/soiling - suggests impaction
Focused examination
- Abdominal exam - distension, palpable faecal loading, mass
- PR exam mandatory - impaction, mass, fissure, rectal tone, prolapse
- Cognitive and mobility assessment (functional contributors)
- Signs of hypothyroidism
Investigation strategy
- Bloods if red flags/new presentation - FBE, UEC, calcium, TSH, glucose
- Abdominal X-ray - only if impaction extent/obstruction uncertain clinically, not routine
- Colonoscopy - if red flags, or per screening/overdue surveillance
- Avoid over-investigating chronic stable functional constipation in known frail patient - clinical reassessment often sufficient
Management
1. Treat reversible/secondary cause - deprescribe/reduce opioids and anticholinergics where possible, correct hypercalcaemia/hypothyroidism
2. Non-pharmacological - fluid, fibre (if adequate intake feasible - high fibre can worsen symptoms in slow transit/immobile frail patients), mobilisation, scheduled toileting after meals (gastrocolic reflex), private/dignified toileting environment
3. Laxatives - stepwise
| Class | Example | Note |
|---|---|---|
| Osmotic | Macrogol (first-line) | Preferred - effective, well tolerated |
| Stimulant | Senna, bisacodyl | Add if osmotic alone inadequate; first-line if opioid-induced alongside osmotic |
| Stool softener | Docusate | Adjunct, weak evidence alone |
| Opioid-induced | Naloxegol / methylnaltrexone | If opioid-induced constipation refractory to standard laxatives |
- Disimpaction - oral macrogol high-dose regimen first; enema/manual evacuation if refractory or severe
- Address ongoing prevention post-disimpaction - relapse is common without maintenance laxative + review
Traps
- Missing malignancy behind "constipation" in a new presentation >50yo
- Overflow diarrhoea from impaction misdiagnosed and treated with antidiarrhoeals - worsens impaction
- Reflexive high fibre in an immobile, low-fluid-intake frail patient -> worsens bloating/obstruction risk
- Not reviewing opioid/anticholinergic burden as the actual driver
Talk track
New bowel habit change in older patient = exclude malignancy first (PR exam, red flags, colonoscopy if indicated). Otherwise think secondary causes - drugs (opioids, anticholinergics), immobility, hypothyroidism/hypercalcaemia - before labelling functional. Manage stepwise: deprescribe/treat cause, then osmotic laxative (macrogol) first-line, add stimulant if needed; disimpaction if impacted, with maintenance laxative afterward to prevent recurrence.
8 of 8 sections written · drafted 2026-09-13