A Prospective Study Comparing the Diagnostic Ability of Abdominal Ultrasonography with Computed Tomography in Cases Suspected of Retaining the Patency Capsule.

OBJECTIVES

Patency capsule (PC) testing is widely used to assess small-bowel patency before small-bowel capsule endoscopy (SBCE). Although abdominal computed tomography (CT) reliably identifies PC location, routine use is limited by radiation exposure and cost. Abdominal ultrasonography (AUS) is a noninvasive, radiation-free alternative; however, its diagnostic accuracy for PC localization remains unclear.

METHODS

We conducted a prospective, exploratory, single-center study in patients in whom PC excretion could not be confirmed within the predefined observation period. All patients underwent AUS followed by CT on the same day. The primary endpoint was the sensitivity of AUS for detecting small-bowel PC retention using CT as the reference standard. Secondary endpoints included the PC visualization rate, diagnostic accuracy for small bowel versus colon classification, six-segment agreement between AUS and CT, and SBCE retention after AUS-based assessment.

RESULTS

Thirty-four patients were included. AUS visualized the PC in 28 patients (82.4%). All six patients with small-bowel retention on CT were correctly identified as "small bowel" by AUS (sensitivity 100%; 95% confidence interval [CI], 61.0-100). Among 28 patients with colonic PC on CT, AUS classified 22 as "colon," yielding a sensitivity of 78.6% (95% CI, 60.5-89.9). Six-segment agreement between AUS and CT was 82.4% overall and 100% among visualized cases. No SBCE retention occurred after AUS-based colonic classification.

CONCLUSIONS

AUS accurately detected small-bowel PC retention and showed good agreement with CT when visualization was achieved. Although non-visualized findings require cautious interpretation, AUS may serve as a useful first-line imaging modality for evaluating PC location prior to SBCE.

TRIAL REGISTRATION: N/A.