Closed-loop obstruction or strangulation: emergency laparotomy. Warning signs are continuous (rather than colicky) pain, peritonism, fever, tachycardia and a rising lactate.
Small bowel obstruction
- Colicky pain, early vomiting, later constipation
- Central distension, valvulae conniventes crossing the lumen on imaging
- Adhesions and hernias are the commonest causes
Large bowel obstruction
- Constipation and distension first, vomiting late
- Colorectal cancer until proven otherwise
- Sigmoid volvulus: coffee-bean sign; caecal volvulus; check for a competent ileocaecal valve (closed loop)
Partial / early
- Colic, distension, some flatus
- Drip and suck, NG tube
- Conservative trial, review
Complete obstruction
- No flatus or stool, vomiting
- CT for level and cause
- Surgical review
Strangulation / ischaemia
- Constant pain, peritonism, high lactate
- Fever, tachycardia, shock
- Resuscitate and urgent surgery
Approach
1
1. Resuscitate
IV fluids and drip and suck (NG tube on free drainage, nil by mouth). Correct K+ and Mg2+, catheterise and chart fluid balance, analgesia.
IV fluids and drip and suck (NG tube on free drainage, nil by mouth). Correct K+ and Mg2+, catheterise and chart fluid balance, analgesia.
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2
2. Imaging
CT abdomen and pelvis is the investigation of choice: find the transition point, cause, closed loop, ischaemia or perforation. Erect chest X-ray for free air.
CT abdomen and pelvis is the investigation of choice: find the transition point, cause, closed loop, ischaemia or perforation. Erect chest X-ray for free air.
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3
3. Conservative trial
Reasonable for adhesional SBO without ischaemia or peritonism: continue drip and suck and review. A water-soluble contrast study can be both diagnostic and therapeutic.
Reasonable for adhesional SBO without ischaemia or peritonism: continue drip and suck and review. A water-soluble contrast study can be both diagnostic and therapeutic.
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4
4. Operate
Peritonitis, closed loop, ischaemia, strangulated hernia, failed conservative management, or an obstructing cancer (stent, defunction, or resection).
Peritonitis, closed loop, ischaemia, strangulated hernia, failed conservative management, or an obstructing cancer (stent, defunction, or resection).
Red flags for ischaemia
- Pain out of proportion or now continuous
- Fever, tachycardia, rising lactate
- Peritonism or a tender irreducible hernia
Pitfalls
- Labelling as constipation without imaging
- Missing a strangulated hernia (examine all hernial orifices)
- Delaying surgery while fluid resuscitating a closed loop
- Forgetting a rectal exam and groin exam
MedPrep - www.medprep.uk - Educational revision aid only. Not clinical guidance. Doses are adult examples; check the BNF, current guidelines and local policy, and seek senior advice. Nov 2026