Assessment of Urinary Tract Calculi With 64-MDCT: The Axial Versus Coronal Plane

Abstract

The objective of our study was to compare the detection rate, conspicuity, and size measurements of urinary tract calculi on coronal reformations versus the axial plane using 64-MDCT. For this retrospective study, 80 consecutive CT examinations performed for clinical diagnosis of renal colic or for the assessment of known nephrolithiasis were evaluated. All studies were stripped of patient identifiers, and the axial and coronal plane images of each study were randomized and presented to two abdominal radiologists. For each study, the radiologists recorded the number and location of stones, diagnostic confidence and stone conspicuity (subjectively on a 2-point scale), and stone size. The standard of reference was data from a consensus reading with the study coordinator examining the same parameters on images in both planes of each patient. Detection rates were compared between planes using logistic regression with generalized estimating equations to account for multiple stones per patient. On consensus reading, 272 stones were identified. For all renal stones, the coronal plane detected more stones as compared with the axial plane (p < 0.001). For stones smaller than 5 mm, a higher proportion received the maximal conspicuity score on the coronal plane than on the axial plane (p < 0.001). Both reviewers better estimated stone size on the coronal plane than the axial plane (p = 0.02); their axial plane measurements underestimated stone size by 13.4% (mean). The detection of stones and estimation of maximal stone diameter were improved using coronal reformations. The conspicuity of stones and diagnostic confidence in identifying stones smaller than 5 mm in diameter were also improved on the coronal plane.