Diagnostic Approach for Small Bowel Obstruction

Introduction to Diagnostic Modalities

The American College of Radiology recommends CT abdomen and pelvis with IV contrast as the initial imaging modality for suspected small bowel obstruction in adults, due to its ability to provide critical information about the site and cause of obstruction, potential complications, and 3D anatomical relationships 4, 5
The Journal of the American College of Radiology states that CT provides much more information about the status of the entire gastrointestinal tract, the 3D anatomy, and the underlying causes and complications of small bowel obstruction 3

Ultrasound has limited reliability in characterizing different etiologies of surgical abdomen, including small bowel obstruction, with a sensitivity of 91% and specificity of 84% in some studies, but significant limitations compared to other imaging modalities 1, 3
The American College of Radiology notes that ultrasound is highly operator-dependent and can yield equivocal results, with inherent limitations in adults for diagnosing intestinal obstruction, particularly in visualizing the entire bowel tract and determining the exact site of obstruction 3, 9

For adults, CT abdomen and pelvis with IV contrast is the recommended initial imaging modality, as it provides critical information about the site and cause of obstruction, potential complications, and 3D anatomical relationships 4, 5
For children and pregnant patients, abdominal ultrasound is recommended as the initial diagnostic imaging modality, with CT or MRI suggested as subsequent imaging if initial ultrasound results are negative, equivocal, or non-diagnostic 9

Ultrasound can detect hypo/anechoic free fluid in the peritoneal cavity, which may be present in cases of obstruction with complications, and may be useful as an initial screening tool when CT is unavailable 1, 2
In the pediatric population, ultrasound has proven useful in evaluating specific causes of small bowel obstruction such as intussusception and midgut volvulus 3