Small Bowel Obstruction: Medical Management
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Direct answer
Strangulation, not the obstruction itself, is what kills in small bowel obstruction, so the medical job is threefold: resuscitate and decompress ("drip and suck"), recognise who is strangulating, and decide who needs theatre. Most adhesive obstruction settles conservatively, and a water-soluble contrast challenge at 24 hours both treats and predicts. In India the cause list differs from Western textbooks — abdominal tuberculosis and hernias sit beside post-operative adhesions, and the hernial orifices must be examined in every patient.
What you must remember
- Causes, ranked for India: adhesions after previous surgery, irreducible external hernia (always examine all orifices), abdominal tuberculosis — adhesive bands and ileocaecal strictures (obtain tissue for NTEP-linked CBNAAT when surgery happens), malignancy, Crohn's disease, and gallstone ileus in the elderly.
- Strangulation signs: constant (not colicky) pain, fever, tachycardia, localised peritonism, leucocytosis, metabolic acidosis, and rapidly rising requirements — these convert "observe" into "operate".
- Closed loop and caecal danger: a closed-loop obstruction risks rapid gangrene; caecal diameter above roughly 9 cm threatens perforation in large bowel obstruction.
- Imaging logic: erect abdominal X-ray shows centrally placed, step-ladder dilated loops with valvulae conniventes; CT distinguishes mechanical obstruction from ileus and locates the transition point.
- Conservative care: nil orally, nasogastric decompression, IV Ringer lactate with potassium correction, analgesia, serial examination every few hours.
- Gastrografin challenge: water-soluble contrast given via the NG tube; contrast reaching the colon by 24 hours predicts successful resolution (and may be therapeutic), while contrast stuck at the transition point predicts failure.
- Surgery indications: clinical strangulation, closed loop, irreducible hernia, and failure of conservative care — not merely "no improvement by a fixed hour" in a stable, improving patient.
The 24-hour contrast test
Consider a 46-year-old man, six years after an open cholecystectomy, with 24 hours of colicky vomiting, distension and obstipation. Resuscitation first: two litres of Ringer lactate for his tachycardia and oliguria, potassium replaced, NG tube passed yielding a litre of faeculent fluid, and he is made nil orally. Examining the hernial orifices excludes the cheap diagnosis; a plain X-ray shows central dilated loops. He is tender but has no peritonism, no fever, and a normal lactate — adhesive obstruction, conservative pathway. At hour twelve a Gastrografin follow-through is arranged: if contrast is seen in the caecum and colon by 24 hours, his likelihood of avoiding surgery is high, the contrast itself may relieve the obstruction by its osmotic effect, and the team continues "drip and suck" with confidence. Contrast arrested at a fixed transition point, or any new peritonism overnight, takes him to theatre. Had he instead presented with a week of night sweats, evening fever and a doughy abdomen — the ileocaecal tuberculosis picture — the plan bends toward tissue diagnosis, anti-tuberculosis therapy and its oblique strictures, not a mere adhesiolysis.
The hernia nobody examined
The exam scenario that traps candidates is the elderly woman with small-bowel obstruction who never had surgery: the cause is almost certainly an irreducible femoral hernia hiding in a fat thigh, found only if the hernial orifices are examined — a stock viva lesson. The second favourite is gallstone ileus in an elderly patient without hernia or scars: the Rigler triad on imaging — small bowel obstruction, pneumobilia, and an ectopic calcified gallstone — explains a pathophysiology worth reciting (cholecysto-duodenal fistula). Third, ileus versus mechanical obstruction: in post-operative ileus there is painless distension with no colic and no transition point; feeding early and correcting electrolytes beats waiting.
Frequently asked questions
What are the signs of strangulation in bowel obstruction?
Constant localised pain, fever, tachycardia, peritonism, leucocytosis and metabolic acidosis — indicating ischaemia that mandates immediate surgery.
How does the water-soluble contrast study help?
Gastrografin reaching the colon within 24 hours predicts resolution of adhesive obstruction and may be therapeutic, whereas contrast held at the transition point predicts the need for surgery.
Why does tuberculosis matter in Indian SBO lists?
Abdominal tuberculosis causes adhesive bands and oblique ileocaecal strictures, is common, and requires tissue diagnosis with anti-tuberculosis therapy rather than surgery alone.
What is the Rigler triad?
Small bowel obstruction, pneumobilia and an ectopic gallstone — the imaging signature of gallstone ileus via a cholecysto-enteric fistula.
What is "drip and suck"?
Nasogastric decompression combined with intravenous fluid and electrolyte replacement — the foundational conservative management of uncomplicated adhesive obstruction.