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Bowel obstruction
Drip and suck buys time — strangulation doesn't give you any. Confirm it, decide small or large bowel, find the cause, and look for the features that mean ischaemia or impending perforation. Most adhesional obstructions settle; strangulated, closed-loop and hernia-related ones need theatre. Built for revision, not live patient decisions.
Settle them, and check the basics
resuscitate · decompressRed flags — what each should make you think
Always examine the hernial orifices, including femoral, in every patient with obstruction. A small strangulated femoral hernia in an elderly woman is easy to miss and deadly. And in a patient with no previous surgery, think cancer until proven otherwise.
"Drip and suck" — the first actions
- IVIV fluids + electrolytes
- NGNasogastric tube
- NBMNil by mouth
- UOCatheter
- CTCT abdomen/pelvis with contrast
- ☎Surgical review
Understand the patient
small vs large · causeSmall vs large bowel
- Small bowel — earlier vomiting (often bilious), central colicky pain, less distension. Causes: adhesions (most common), hernias, Crohn's strictures, gallstone ileus, tumours
- Large bowel — more distension, constipation then absolute (no flatus), later vomiting (faeculent). Causes: colorectal cancer, diverticular stricture, volvulus (sigmoid, caecal)
- Pseudo-obstruction — colonic dilatation without a mechanical cause (elderly, post-op, electrolytes, drugs); CT shows no transition point
Adhesional SBO — the water-soluble contrast challenge
- If no signs of strangulation: give water-soluble contrast (e.g. Gastrografin) via NG tube, then AXR at about 6–24 h
- Contrast reaching the colon predicts resolution without surgery (and may speed it up)
- No improvement → surgery
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Pain becomes constant, peritonism, fever, tachycardia, raised WCC/lactate.
CT signs: reduced bowel wall enhancement, mesenteric oedema, free fluid, pneumatosis.
Emergency laparotomy after resuscitation.
Large bowel obstruction with a competent ileocaecal valve — the caecum dilates relentlessly; or a small bowel loop twisted at two points.
CT; caecum over 9–12 cm is a perforation risk.
Urgent surgery or decompression (stent/stoma) — senior surgical decision.
Elderly, constipation, neuro/psychiatric comorbidity; massive distension.
AXR (coffee bean), CT.
Endoscopic (flexible sigmoidoscopic) decompression with flatus tube if no ischaemia; surgery if ischaemic or recurrent.
Painful, tense, irreducible lump at a hernia site with obstruction.
Clinical, CT.
Emergency surgery. Don't try forceful reduction. See the hernias page.
Sudden worsening, peritonism, sepsis.
CT / erect CXR.
Emergency surgery. See the perforation page.
Investigate — what to order, when, and what it tells you
test with a question in mindBloods
CT abdomen/pelvis (IV contrast)
AXR
Risk
How the plan comes together
disposition · handoversurgical ward
Adhesional SBO without strangulation: drip and suck, contrast challenge, daily review.
theatre / HDU
Strangulation, closed loop, hernia, perforation, failed conservative management, or large bowel obstruction needing decompression.
Hand over: cause, CT findings, NG output, fluid balance, lactate, NELA score, surgical plan.
Drip and suck, CT, and a surgical review — then look hard for anything that means ischaemia: constant pain, peritonism, fever, raised lactate, a closed loop or a strangulated hernia. Nicely done getting here.
Clerking template
copy or downloadBowel obstruction — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 11 knownFrequently asked questions
quick answersWhat are the red flags for bowel obstruction?
- Constant (not colicky) pain, peritonism — think strangulation / ischaemia
- Fever, tachycardia, high lactate — think ischaemic bowel
- Irreducible tender lump at a hernia site — think strangulated hernia
- Caecum over 9–12 cm on imaging — think closed loop — perforation risk
- Huge distended abdomen, elderly, "coffee bean" on AXR — think sigmoid volvulus
- No previous surgery, no hernia — think think malignancy
What is the initial management of bowel obstruction?
- IV fluids + electrolytes — patients are often very dry; correct K⁺
- Nasogastric tube — free drainage — decompresses and reduces aspiration risk
- Nil by mouth — analgesia and antiemetic
- Catheter — strict fluid balance
- CT abdomen/pelvis with contrast — confirms, finds the cause and signs of ischaemia
- Surgical review — early — NELA risk-score if emergency laparotomy considered
Always alongside senior support and your local guideline.
What diagnoses must you not miss in bowel obstruction?
- Strangulation / ischaemic bowel — constant pain · lactate
- Closed-loop obstruction — competent ileocaecal valve
- Sigmoid volvulus — elderly · "coffee bean"
- Strangulated hernia — tender irreducible lump
- Perforation — free air
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for bowel obstruction?
- Bloods — FBC, U&E (dehydration, K⁺), CRP, LFT, amylase/lipase, clotting, group and save.
- CT abdomen/pelvis (IV contrast) — Level, cause, transition point, closed loop, ischaemia, perforation.
- AXR — Quick look: dilated loops (small bowel over 3 cm, colon over 6 cm, caecum over 9 cm), volvulus; follows contrast studies.
- Risk — Mortality risk to guide consent and level of care.
Admit or discharge: how is the plan decided for bowel obstruction?
- Surgical ward — Adhesional SBO without strangulation: drip and suck, contrast challenge, daily review.
- Theatre / hdu — Strangulation, closed loop, hernia, perforation, failed conservative management, or large bowel obstruction needing decompression.
Is there a clerking template for bowel obstruction?
Yes — there is a free clerking template for bowel obstruction on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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