Measurement of ureteric stone diameter in different planes on multidetector computed tomography - Impact on the clinical decision making

Objective To determine if the measurement of ureteric stone in coronal reconstruction plane is different from the measurement in axial plane and whether the difference can impact the management decision in patients with ureteric colic. Methods All patients who underwent unenhanced multidetector computed tomographic (MDCT) scan for the evaluation of reno-ureteral colic in outpatient clinics and emergency room were evaluated. The scans were evaluated on Picture Archiving Computer System with a 3-mm axial and reformatted 3-mm coronal sections. Maximal stone diameter was measured in 2 dimensions in the axial and reformatted coronal sections by 2 reviewers. Only scans with isolated, unilateral, solitary ureteric calculi were included in the final analysis. All patients were monitored up to 4 weeks after MDCT to determine the clinical outcome. Results A total of 331 patients (272 male and 59 female; mean age ± standard deviation, 39.8 ± 13.8 years) were included. One hundred seventy-one (51.7%) stones passed spontaneously during the follow-up period. There was a 20% underestimation of maximal stone diameter in axial plane for all stones and a 17% for the stones that passed spontaneously or with medical expulsive therapy, as compared with measurement on coronal reconstruction. Conclusion Measuring the transverse stone diameter on axial images of MDCT scan underestimates size of ureteric stone. This can have an impact on counseling of patients and their clinical outcome, coronal reformatted images be used for size estimation.