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Small bowel obstruction
In small bowel obstruction the key question is not "is it obstructed?" but "is it strangulated?": adhesive obstruction without strangulation is first managed conservatively, while strangulation, a closed loop or an incarcerated hernia need urgent surgery.
Why it matters in the exam
The typical case is a patient with previous abdominal surgery who has colicky pain, vomiting, distension and no passage of flatus. Questions test the order of actions: fluid resuscitation, correction of electrolytes, a nasogastric tube, and CT with intravenous contrast to find the transition point and the cause. Then you must recognise the signs that demand surgery — fever, tachycardia, constant rather than colicky pain, peritoneal tenderness, raised lactate, and on imaging a non-enhancing wall, mesenteric oedema and a closed loop.
Further questions cover conservative treatment itself: a water-soluble contrast agent used both as a predictive test and as a treatment, and how long it is reasonable to wait before deciding on surgery. In an abdomen that has never been operated on, think of a hernia (including femoral and obturator hernias in older women), a tumour and gallstone ileus. It is also worth knowing the electrolyte disturbance caused by prolonged vomiting, and the difference between mechanical obstruction and post-operative paralytic ileus.
Key points
- The most common cause in adults is post-operative adhesions; then hernia and tumour.
- CT with intravenous contrast shows the transition point, the cause and signs of strangulation.
- Strangulation or a closed loop — urgent surgery.
- Without strangulation: nil by mouth, nasogastric tube, fluids and electrolytes; water-soluble contrast predicts and treats.
- No improvement after 72 hours — surgery.
Summary table
| Topic | Finding | Meaning or action |
|---|---|---|
| Causes | Post-operative adhesions (most common in adults), incarcerated hernia, tumour, Crohn's disease | In a never-operated abdomen — look for a hernia and a tumour |
| Abdominal X-ray | Small bowel loops wider than 3 cm, air-fluid levels, little gas in the colon | Initial test; CT is the decisive test |
| CT with intravenous contrast | Transition point: dilated bowel above, collapsed bowel below | Shows the cause, the degree of obstruction and signs of strangulation |
| Signs of strangulation | Fever, tachycardia, constant pain, peritoneal tenderness, raised lactate; on CT a non-enhancing wall, mesenteric oedema, a closed loop | Urgent surgery |
| Adhesive obstruction without strangulation | Nausea, vomiting, distension, no peritoneal signs | Nil by mouth, nasogastric tube, fluids and electrolyte correction; water-soluble contrast |
| Failed conservative treatment | No improvement after 72 hours, or deterioration at any point | Surgery (laparoscopy or laparotomy) |
A free exam question
בת 59 עברה לפני 3 .שנים כריתת מעי דק. סובלת מחסימות מעי דק חוזרות. פנתה כעת בשל כאבי בטן בקבלתה לחדר מיון לחץ דם 110/81 ,ממ"כ דופק 109 פעימות לדקה. בבדיקתה: בטן תפוחה, רגישות בבטן התחתונה וסימני גירוי ציפקי ממוקמים .בצילום בטן ריקה, סימנים של חסימה חלקית של המעי הדק. מהו הצעד הבא בניהול המקרה? (the question as examined, in Hebrew)
- א. הכנסת זונדה, נוזלים והמשך השגחה במחלקה
- ב. צילום בליעה
- ג. טיפול ניתוחי
- ד. צילום ביקורת כעבור 6 שעות
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Sources
- Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (WSES), 2017 update (published 2018) — Diagnosis, non-operative management and indications for surgery
- ACR Appropriateness Criteria: Suspected Small-Bowel Obstruction, 2019 — Imaging in suspected small bowel obstruction
- Sabiston Textbook of Surgery, 21st edition (2022) — Small Intestine
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.