Acute appendicitis: added diagnostic value of coronal reformations from isotropic voxels at multi-detector row CT

Abstract

Purpose: To assess retrospectively the added value of coronal reformations from isotropic voxels obtained with 16-section multi-detector row computed tomography (CT) of the abdomen and pelvis in patients with suspected acute appendicitis.

Materials and methods: This study was approved by the institutional review board, and informed consent was waived. One hundred consecutive patients (21 men, 79 women; mean age, 38 years) with suspected appendicitis underwent 16-section multi-detector row CT (section thickness, 0.625 mm; pitch, 1.75; table speed, 35 mm/sec [17.5 mm per rotation, two rotations]; and gantry speed, 0.5 second per rotation), with coronal reformations. Twenty-four patients had appendicitis; 76 did not. Protocol included 150 mL oral iopamidol administered at 3 mL/sec. Transverse scans were reconstructed with 5-mm-thick sections at 5-mm intervals and 0.625-mm-thick sections at 0.625-mm intervals. The second data set was reformatted coronally, with 3-mm-thick sections at 5-mm intervals. Three independent blinded readers interpreted transverse scans alone and then coronal scans; confidence in visualization of any portion of appendix, entire appendix, wall thickening, distention, inflammation, fluid, and appendicitis was scored with 1-5 scale. Sensitivity and specificity were determined for each reader and compared by means of signed rank test. Agreement between readers was determined with kappa statistic. Differences in mean confidence ratings for each finding were determined with Wilcoxon signed rank test.

Results: Mean sensitivity and specificity for all three readers together were 96% and 95% for transverse reformations alone and 95% and 94% for combined transverse and coronal reformations (not significant), respectively. Visualization rates for portion or all of appendix were higher for combined transverse and coronal reformations than for transverse reformations alone (higher mean confidence scores: 0.23 higher [P < .009] and 0.51 higher [P < .001], respectively). In patients without appendicitis, transverse and coronal reformations together enhanced confidence in exclusion of wall thickening, distention, and fluid (lower confidence scores: 0.21 lower [P < .001], 0.17 lower [P < .01], 1.00 lower [P < .001], respectively). Combined transverse and coronal reformations enhanced confidence in identification of appendix in mean of 57 patients. Combined transverse and coronal scans helped exclude appendicitis in mean of 38 patients and aided diagnosis of it in 15.

Conclusion: Sixteen-section multi-detector row CT transverse and coronal reformations are equally sensitive and specific for diagnosis of appendicitis. Coronal reformations improve confidence in visualization of appendix (whether diseased or normal) and in diagnosis or exclusion of appendicitis.