Oral Board Case: Small Bowel Obstruction (SBO)

What is your initial differential and what features of this presentation point you toward small bowel obstruction?

Expected answer

Crampy pain, nausea, vomiting, obstipation, distension, and high-pitched bowel sounds in a patient with prior abdominal surgery are classic for mechanical SBO. The leading cause is adhesive disease given her prior hysterectomy and abdominal operations. Differential includes incarcerated hernia, malignancy, internal hernia, volvulus, ileus, and large bowel obstruction. I'd commit to adhesive SBO as most likely but keep strangulation and closed-loop obstruction in mind.

Walk me through your initial workup and management on arrival.

Expected answer

Simultaneously resuscitate and evaluate: place an NG tube for decompression, two large-bore IVs, and begin IV crystalloid resuscitation with electrolyte replacement, with urine output as my endpoint. I'd take a focused history (prior surgeries, prior obstructions, bowel habits, symptom progression) and exam looking for dehydration, hernias, peritonitis, and a digital rectal exam to rule out an obstructing mass. Labs: CBC, BMP, lactate, INR. Imaging: upright/supine abdominal films followed by CT abdomen/pelvis with oral and IV contrast.

What CT findings would tell you this is uncomplicated adhesive SBO versus something that needs the OR?

Expected answer

Uncomplicated SBO shows dilated proximal loops (>3 cm) with air-fluid levels and distal decompression at a transition point, often with a fluid-filled stomach. Concerning features mandating operation include a closed-loop configuration, mesenteric edema, nonphysiologic free fluid, pneumatosis intestinalis, portal venous gas, free air, lack of bowel wall enhancement, or a high-grade obstruction with a tight transition point and no distal contrast.

Adhesive SBO shouldn't cause major derangements—so what lab findings concern you?

Expected answer

Significant leukocytosis, lactic acidosis, or hemodynamic/electrolyte instability not explained by simple hypovolemia suggest compromised bowel and lower my threshold to operate. A mild leukocytosis from bowel edema and hypovolemia should normalize with NG decompression and resuscitation. Importantly, a normal lactate does not rule out ischemia, particularly with venous outflow obstruction or a closed loop.

Her exam shows distension and tenderness but no peritonitis, stable vitals, and CT shows a transition point without ischemic signs. What is your plan?

Expected answer

This is a candidate for a 24–48 hour trial of nonoperative management: continue NG decompression, IV fluids, electrolyte correction, and serial abdominal exams. I'd consider a water-soluble contrast (Gastrografin) challenge, which is both prognostic and therapeutic—if contrast reaches the colon, it predicts resolution and may shorten time to recovery. If she resolves, I remove the NG and advance diet slowly. If she fails to resolve or develops worsening exam/labs, she goes to the OR.

What clinical changes during the nonoperative trial would prompt you to operate?

Expected answer

Development of peritoneal signs, fever, worsening tachycardia or hypotension unresponsive to fluids, rising leukocytosis, new or worsening lactic acidosis, or failure of the obstruction to resolve within 24–48 hours. Any sign of strangulation or ischemia ends the trial immediately and the patient goes to the OR.

You take her to the OR. Describe your operative approach and intraoperative decision-making.

Expected answer

For an adhesive SBO I'd perform exploration—open via prior midline incision, or laparoscopy in selected cases with limited adhesive burden and a stable patient. I'd carefully lyse adhesions, identify and relieve the transition point, and run the entire bowel. I assess bowel viability by color, peristalsis, mesenteric pulsation, and bleeding edges; warm packing and reassess marginal segments. Frankly necrotic or nonviable bowel is resected with primary anastomosis if the patient is stable and bowel ends are healthy. I'd avoid enterotomy during adhesiolysis and repair any serosal injuries.

Which patient subgroups change your threshold for operation, and why?

Expected answer

Virgin abdomen (no prior surgery)—lower threshold given concern for malignancy or hernia, though adhesions remain common. Prior Roux-en-Y/altered anatomy—high risk for internal hernia (swirl sign, dilated loops with intervening decompressed bowel); many advocate diagnostic laparoscopy. Hernia with a narrow neck—high strangulation risk; do not reduce if strangulation suspected, take to OR. Impaired/elderly/obtunded/immunosuppressed or steroid patients—unreliable exam and blunted signs of ischemia, so lower threshold to operate.

What is your postoperative management after adhesiolysis with bowel resection?

Expected answer

Continue resuscitation and electrolyte correction, monitor urine output, maintain NG decompression until evidence of return of bowel function, then advance diet. Watch for ileus, anastomotic leak (fever, tachycardia, peritonitis, leukocytosis), recurrent obstruction, and wound complications. VTE prophylaxis and early mobilization. Counsel the patient on recurrence risk given adhesive disease.