Management of constipation in the elderly (including pharmacological management and complications)

Management of constipation in the elderly (including pharmacological management and complications)

Constipation is defined by Rome IV criteria — straining, hard or lumpy stools, sensation of incomplete evacuation, anorectal blockage, need for manual manoeuvres, or fewer than three spontaneous bowel movements weekly, for at least 3 of the last 6 months.

Pathy's makes a key teaching point: when comorbidities are controlled for, constipation is no commoner in the elderly than in the young, and stool frequency does not change with age. What older people complain of is straining and hard stools.

Laxative use, not constipation itself, rises steeply with age. Complaints and laxative consumption are both very common in older people.

Age-related changes that do matter: slower colonic peristalsis, reduced anal sphincter tone, and in older women, impaired rectoanal angle and perineal descent after obstetric trauma — so elderly women have more rectal evacuation problems than elderly men.

Constipation reduces quality of life, lowers self-perceived health, worsens urinary frequency, urgency and dysuria, and its treatment improves mood, sexual function and continence.

Pathy's is explicit that most causes relate to medication use or coexisting medical illness, not to ageing.

Commonest drugs: opiates, calcium channel blockers (verapamil worst), NSAIDs and anticholinergics. Also iron, antipsychotics, tricyclics, antiparkinsonian drugs, diuretics.

Secondary causes: hypothyroidism, hypercalcaemia, hypokalaemia, diabetes, Parkinson's disease, stroke, dementia, depression, spinal cord lesions, colorectal cancer, strictures.

Pathophysiological types: normal-transit (commonest), slow-transit, and dyssynergic defecation (pelvic floor dyssynergia) — the last is important because it responds to biofeedback and not to laxatives.

Pathy's notes that immobility and low fluid/fibre intake are often blamed but poorly supported by evidence — increased physical activity does not reliably improve constipation.

History with the Bristol Stool Form Scale, full drug review, and a mandatory digital rectal examination to detect impaction, reduced tone, and dyssynergia.

Red flags demanding colonoscopy: rectal bleeding, anaemia, weight loss, new change in bowel habit, family history of colorectal cancer, age with overdue screening.

Pathy's principle: in patients with up-to-date colorectal cancer screening and no worrying symptoms, empirical treatment is appropriate; testing is reserved for those who fail to respond.

Second-line testing when refractory: colonic transit study, anorectal manometry with balloon expulsion, and defecography. A plain abdominal radiograph helps assess stool load or confirm high impaction.

Step 1 — Review and remove: stop or substitute constipating drugs; switch verapamil to another calcium channel blocker; increase dietary fibre and fluids as a universally accepted first step (though of limited evidence).

Step 2 — Bulking agents: psyllium 3–6 g, bran 4–10 g, methylcellulose 2–4 g. Pathy's warns they must be avoided in faecal impaction, bed-bound patients and those with poor fluid intake; side effects are bloating and flatulence.

Step 3 — Osmotic laxatives: PEG (macrogol) 17–34 g is the best tolerated overall in elders and improves both stool consistency and frequency; lactulose 10–40 g and sorbitol 70% 15–60 mL are alternatives but cause bloating and cramps through bacterial fermentation.

Magnesium and saline salts should generally be avoided in the elderly — risk of hypermagnesaemia even with normal renal function; contraindicated in renal disease, end-stage liver disease and heart failure.

Step 4 — Stimulant laxatives: senna 15 mg, bisacodyl 5–10 mg, sodium picosulfate 5–10 mg. Most commonly combined with an osmotic agent when a single drug fails.

Step 5 — Second-line prescription agents: lubiprostone 8–24 µg twice daily (chloride channel activator) is specifically endorsed by Pathy's for elders; prucalopride, a 5-HT4 agonist, is useful in refractory cases.

Stool softeners (docusate) have no evidence base — Pathy's records no RCT showing efficacy, one trial showing no benefit over placebo, and psyllium proving superior. The faecal incontinence chapter states bluntly that docusate is ineffective and should not be prescribed.

Opioid-induced constipation: use PAMORAs — naloxegol, naldemedine, methylnaltrexone — which reverse constipation without reversing analgesia or precipitating withdrawal. Pathy's calls methylnaltrexone "an important advance", reserved for refractory cases as it is injected on alternate days.

Enemas and suppositories: small-volume tap water enemas and arachis oil retention enemas (check nut allergy) are useful; phosphate enemas cause serious hyperphosphataemia in renal impairment; large tap-water enemas can cause hyponatraemia; soap-suds enemas should never be used.

Non-pharmacological and special situations: biofeedback is the mainstay for dyssynergic defecation, effective in around 70% over 4–6 sessions and superior to diet, exercise, laxatives or diazepam. In dementia, prevention with a regular osmotic laxative is preferred; non-verbal cues of a need to defecate include fidgeting, pacing and pulling at clothes.

Refractory disease: nearly 90% of slow-transit constipation responds to laxatives; subtotal colectomy with ileorectal anastomosis is rarely needed and only after dyssynergia has been treated. Antegrade enemas via caecostomy are a last resort with limited evidence.

Faecal impaction — present in about 7% of institutionalised elderly on rectal examination. The first sign is often overflow diarrhoea and rectal incontinence; without a rectal examination it is misdiagnosed and wrongly treated with antidiarrhoeals.

Further complications: stercoral ulceration and colonic perforation (immobile or cognitively impaired patients), faecal incontinence, urinary retention and urinary symptoms, haemorrhoids and anal fissure, rectal prolapse, sigmoid volvulus, delirium and agitation in dementia, and laxative-related electrolyte disturbance.

Management of impaction: Pathy's states the optimal treatment is not clear — oral PEG or other osmotic laxatives with or without enemas if tolerated; manual disimpaction for a hard or large rectal bolus; hyperosmotic water-soluble contrast enemas have also been used successfully. Bulking agents must be avoided in this group.