The limited use of ultrasound in the detection of abdominal abscesses in patients after colorectal surgery: compared with gallium scan and computed tomography

BACKGROUND/AIMS: Ultrasound has been suggested to be a first-line test for the detection of intra-abdominal abscess (IAA). However, according to our experience, ultrasound seemed not so effective when applied to the patients after colorectal surgery. Computed tomography (CT) and gallium scan have also been suggested as very useful for the detection of IAA. The purpose of this study was to evaluate the efficacy of sonography and gallium scan in diagnosing intra-abdominal abscess after colorectal surgery and to compare these results with CT. METHODOLOGY: Twenty-three patients with suspected IAA after colorectal surgery at our institution were eligible for the study. A positive IAA was verifed only if pus was drained or on postmortem examination. Negative reports of abscesses were verified by adequate outpatient review following hospital discharge that indicated the clinical absence of an abscess. Within 4 days of the clinical suspicion of abscess, all patients were evaluated by three techniques: sonography, CT and gallium scan. We compared the sensitivity, specificity and accuracy of these modalities. RESULTS: Fourteen of the 23 patients (60.9%) were verified as IAA. We found the sensitivity, specificity, and accuracy of CT scan for the detection of LAA in the patients with colorectal surgery to be 92.9%, 100%, and 95.7%, respectively. The sensitivity, specificity and accuracy of gallium scan were 100%, 77.8% and 91.3%, respectively. Ultrasound had a 42.9% sensitivity, 100% specificity, and 65.2% overall accuracy for diagnosing IAA. CONCLUSIONS: Sonography plays a small role in the detection of IAA in the patients after colorectal surgery. CT and gallium scan are more helpful than sonography for the detection of IAA.