Synopsis
Differentiate mechanical large-bowel obstruction from acute colonic pseudo-obstruction, detect threatened caecum or bowel early, and sequence resuscitation, decompression, stenting or surgery safely.
- Mechanical large-bowel obstruction has a physical transition point, most often colorectal cancer, diverticular stricture or volvulus; pseudo-obstruction has diffuse functional dilatation without that lesion.
- Progressive distension, colicky pain, obstipation and later faeculent vomiting are typical, but partial obstruction may still pass liquid stool or flatus.
- A competent ileocaecal valve can create a closed loop between an obstructing distal lesion and the valve, rapidly increasing caecal tension and perforation risk.
- Contrast CT defines the transition, cause, proximal diameter, metastatic disease and signs of ischaemia or perforation; a plain radiograph alone rarely completes planning.
- Initial care is fasting, venous access, fluid and electrolyte correction, analgesia, antiemetic treatment, nasogastric decompression when vomiting and urgent colorectal review.
- Malignant left-sided obstruction may be managed with emergency surgery or expert endoscopic stenting as palliation or selected bridge to surgery after multidisciplinary assessment.
- Acute colonic pseudo-obstruction often follows surgery, severe illness, trauma, metabolic disturbance or motility-suppressing medicines and commonly dilates caecum and right colon.
- Pseudo-obstruction starts with treating the precipitant, stopping anticholinergic and opioid burdens, correcting potassium and magnesium, mobilisation and serial diameter assessment.
Key red flags
Progressive abdominal distension, colicky pain and obstipation with a CT transition at an annular mass or benign stricture supports mechanical large-bowel obstruction and needs urgent colorectal planning.
A distal block with a competent ileocaecal valve produces marked caecal dilatation without small-bowel decompression. Increasing pain, tenderness or reduced enhancement threatens caecal perforation.
Abrupt distension and obstruction with a twist, whirl or beak on CT indicates sigmoid or caecal volvulus. Viability and anatomical type determine endoscopic versus operative treatment.
Systemic toxicity with colonic dilatation during severe ulcerative, Crohn's or infectious colitis is not simple pseudo-obstruction and requires urgent medical-colorectal management with anti-inflammatory or infection-directed care.
Investigation priorities
Locate a transition point, identify tumour, stricture or twist, distinguish pseudo-obstruction and assess bowel viability and perforation.
Management branches
Distension, colic and obstipation suggest an occluding colonic lesion.
- Keep fasting, obtain venous access, correct fluid and electrolyte deficits, provide analgesia and antiemetic treatment, and insert a nasogastric tube when vomiting or proximal dilatation warrants it.
- Perform rectal and hernia examination, send urgent bloods and obtain contrast CT with direct radiology discussion about transition, caecal risk, metastases and viability.
- Call senior colorectal surgery early and involve anaesthesia or critical care for physiological compromise; give local antibiotics when perforation, ischaemia or sepsis is suspected.
- Choose resection, diversion or expert stenting according to cause, site, viability, curative intent, comorbidity and available service, documenting stoma and perforation trade-offs.