Synopsis
Distinguish acute colonic pseudo-obstruction from mechanical and toxic colonic dilatation, follow its trajectory, and escalate safely from supportive care to monitored decompression.
- ACPO is a diagnosis of exclusion: CT must exclude a structural obstruction, and acute colitis with systemic toxicity requires a separate toxic-megacolon assessment.
- Correct precipitants, review opioids and anticholinergics, restore fluids and electrolytes, and reassess repeatedly; conservative care is appropriate only while the patient remains uncomplicated and stable.
- New tenderness, peritonitis, fever or physiological deterioration overrides a planned observation period or reassuring diameter and requires urgent surgical reassessment.
Key red flags
New caecal tenderness, guarding, systemic deterioration or rapidly increasing distension suggests threatened viability or perforation. Obtain urgent surgical review even if the caecum has not crossed a memorised size threshold or fewer than 48 hours have elapsed.
Investigation priorities
Exclude a mechanical lesion and assess the dilated colon and its wall.
Management branches
CT and clinical review establish uncomplicated ACPO without a mechanical or toxic cause.
- Review the patient with the surgical team, institute bowel rest and correct dehydration and electrolyte disturbances. Stop or reduce contributory opioids and anticholinergics where feasible, treat the precipitating illness and support mobilisation or regular position changes.
- Use nasogastric decompression when vomiting or upper gastrointestinal distension warrants it and consider a suitable rectal decompression tube. Avoid routine stimulant or osmotic laxatives during active marked dilatation because they may worsen gas and distension.
Key medicines
Neostigmine methylsulfate: plain 2.5 mg/mL injectionFor confirmed adult ACPO after failed supportive care, the South East London Joint Medicines Formulary lists a local off-label option of 2 mg intravenously over 40–60 minutes once, with specialist supervision. In the selected 2.5 mg/mL stock, 2 mg corresponds to 0.8 mL before preparation; this is stock-dose arithmetic, not the prepared administration volume. The administering service must verify its compatible local preparation and delivery method.Do not use with hypersensitivity to neostigmine or excipients, mechanical gastrointestinal or urinary obstruction, peritonitis, doubtful bowel viability or concurrent suxamethonium. Review bradycardia, conduction disease, recent coronary ischaemia, asthma, renal function and any intestinal anastomosis. Administer with continuous ECG and cardiopulmonary assessment, atropine and resuscitation support immediately available; stop and treat significant bradycardia, hypotension or bronchospasm. Use the plain product, not a fixed glycopyrronium combination, and do not infer a repeat, dilution or rescue-dose schedule from this single-dose example.