Intraperitoneal abscesses: diagnostic accuracy of and appearances at MR imaging

To prospectively investigate the diagnostic accuracy of and appearances at magnetic resonance (MR) imaging of patients clinically suspected to have intraperitoneal abscesses.

Sixty-seven consecutive patients underwent MR imaging for suspected intraperitoneal abscesses. MR images were prospectively interpreted for intraperitoneal abscesses; the results were correlated with surgical, histopathologic, and laboratory findings.

MR imaging revealed 25 fluid collections consistent with intraperitoneal abscesses in 22 of 67 patients (33%). Of these collections, 22 were intraperitoneal abscesses; one, a giant sigmoid diverticulum; and two, sterile fluid collections. The latter two patients had been receiving antibiotic therapy. MR imaging allowed exclusion of intraperitoneal abscesses in 45 patients (67%). All collections demonstrated decreased signal intensity on T1-weighted images; on T2-weighted images, 13 collections demonstrated homogeneously increased signal intensity and 12 demonstrated heterogeneously increased signal intensity. The abscesses were best demonstrated on gadolinium-enhanced T1-weighted fat-suppressed images as well-defined fluid collections with peripheral rim enhancement. Sensitivity was 100%; specificity, 94% (95% confidence interval = 83%, 99%); positive predictive value, 88% (95% confidence interval = 69%, 97%); negative predictive value, 100%; and accuracy, 96% (95% confidence interval = 88%, 99%).

MR imaging has high diagnostic accuracy in evaluation of acute intraperitoneal abscesses.