Small bowel obstruction with a closed loop and reduced mural enhancement
A 70-year-old woman presents with 2 days of colicky abdominal pain, vomiting, and absolute constipation. She had an open appendicectomy 30 years ago and a total abdominal hysterectomy 12 years ago. She is otherwise well and takes amlodipine only. Observations: pulse 96/min, blood pressure 142/84 mmHg, temperature 37.6°C. Abdomen is distended and tympanic with mild lower abdominal tenderness but no guarding or rigidity. Bloods: white cell count 13.8 × 10⁹/L, lactate 1.9 mmol/L, creatinine 104 µmol/L, potassium 3.2 mmol/L. CT shows dilated small bowel to 4 cm with a transition point in the right lower quadrant, a 3 cm closed loop with reduced mural enhancement, no free gas, and no oral contrast in the colon. She has been given 1 L of crystalloid and a nasogastric tube, with 300 mL of bilious aspirate.
1. Does the CT finding of a closed loop with reduced mural enhancement mandate immediate surgery, or can she be managed conservatively? Justify your answer.
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It mandates urgent surgery. A closed loop is a surgical emergency because the two obstructed ends create a sealed segment that cannot decompress. As intraluminal pressure rises, venous outflow is obstructed first, then arterial inflow, leading to ischaemia, perforation and peritonitis. Reduced mural enhancement is a radiological sign of impaired perfusion and should be treated as impending or established strangulation, even though her lactate is only 1.9 mmol/L and she has no guarding. Normal lactate and lack of peritonitis do not exclude reversible ischaemia.
A water-soluble contrast challenge is contraindicated because it delays definitive treatment and may worsen distension. I would resuscitate, correct potassium, give antibiotics and proceed to laparoscopy or laparotomy. The operation should divide the adhesive band, assess the bowel for viability, resect clearly non-viable segments, and perform a primary anastomosis only if the remaining bowel is healthy and the patient is stable. A conservative trial would be appropriate for simple adhesive obstruction without a closed loop or ischaemic features, not for this CT.
2. Which clinical and radiological features predict strangulation, and how reliable are they?
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Clinical features include pain out of proportion to examination, persistent tachycardia, fever, localised tenderness or peritonism, leucocytosis, a raised lactate or metabolic acidosis, and failure to improve with nasogastric decompression. In this patient, the pulse of 96/min and white cell count of 13.8 × 10⁹/L are soft signs; the absence of guarding is falsely reassuring.
Radiological features on CT include a closed loop, a U- or C-shaped dilated loop, the whirl sign, reduced or absent mural enhancement, bowel wall thickening, mesenteric stranding, free fluid and pneumatosis or portal venous gas. Reduced enhancement and a closed loop are the most specific, but none is perfectly sensitive. CT has good sensitivity for strangulation but can underestimate reversible ischaemia, and laboratory markers such as lactate rise late. The decision must therefore integrate the CT morphology with serial examination and physiological trends rather than relying on any single feature.
3. If the on-call team decides on a trial of non-operative management, what would you require, and when would you abandon it?
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A trial would only be defensible if the closed loop and reduced enhancement were thought to be artifactual or resolved on repeat imaging, and if there were no peritonitis, haemodynamic instability or metabolic acidosis. It would require continuous or hourly nursing observation, a nasogastric tube, intravenous fluids and electrolyte replacement, analgesia, serial abdominal examination, and repeated lactate and white cell counts. A water-soluble contrast challenge could be used only if closed loop and ischaemia had been excluded, with a plain film after 4–24 hours; contrast reaching the colon predicts resolution.
I would abandon the trial and operate for worsening pain, tenderness or guarding, tachycardia, fever, rising lactate or white cell count, increasing nasogastric output, or failure of contrast to reach the colon. In this patient, the CT findings already meet the threshold for surgery, so a trial would be inappropriate. Documenting the reasoning is important because delay in the presence of a closed loop increases the risk of bowel resection and mortality.