A bowel diameter threshold of ≥2.5 cm, originally derived from the research using computed tomography, is frequently used for diagnosing small bowel obstruction (SBO) with point-of-care ultrasound (POCUS). We sought to determine the optimal bowel diameter threshold for diagnosing SBO using POCUS and its accuracy in predicting surgical intervention.

We conducted a secondary analysis using individual patient-level data from a previous systematic review on POCUS for SBO diagnosis across five academic EDs. Patient data were collected, including imaging results, surgical findings, and final diagnosis. The measured diameter of the small bowel using POCUS was recorded. ROC area under the receiver operating characteristic curves (AUC) were constructed to determine the optimal threshold for bowel diameter in predicting SBO diagnosis and surgical intervention. Subgroup analyses were performed based on sex and age.

A total of 403 patients had individual patient-level data available, with 367 patients included in the final analysis. The most accurate bowel diameter overall for predicting SBO was 2.75 cm (AUC = 0.76, 95% CI 0.71–0.81). A bowel diameter of ≤1.7 cm had 100% sensitivity with no miss rate, while a bowel diameter of ≥4 cm had 90.7% specificity in confirming SBO. Patients under 65 had an optimal threshold of 2.75 cm versus 2.95 cm in patients over 65. Females had an optimal threshold of 2.75 cm, while males had a value of 2.95 cm. There was no significant correlation between bowel diameter thresholds and surgical intervention.

A bowel diameter threshold of 2.75 cm on POCUS is more discriminative diagnostic accuracy for diagnosing SBO. Patients' age and sex may impact diagnostic accuracy, suggesting that tailored approaches may be needed.