Introduction & Objectives
The lithiasic size is a decisive factor to select the most appropriate surgical or medical treatment and evaluate its outcomes. Recent studies support the use of CT in bone window as a standard method to estimate the stone size, however, the high rate of radiation to which patients undergo, requires finding others valid and accessible alternatives such as the ultrasound. To determine differences in lithiasic size estimation between CT in bone window (Gold Standard) and ultrasound with the posterior acoustic shadow measurement as another way to evaluate stone size.
Material & Methods
An In vivo model to analyse 97 renal urolithiasis that were diagnosed in our Center from May 2013 to September 2016. Only 40 stones met the inclusion criteria: to be detected both by close in time CT and ultrasound (2 months maximum between each other). We measured the transversal diameter (D2) in bone window CT using the scanner software (D2BW), ultrasound images (D2US) with a Carestream® software and the posterior acoustic shadow width (D2S) was measured approximately at 1 cm from the stone. We used IBM SPSS Statistics® 20. Differences were analyzed with Wilcoxon test.
The mean stone size was 16.63±1.3 mm CI 95% (13.92-19.33) in bone window CT, 20.49±1.4 mm CI 95%(17.65-23.33) in ultrasound and 20.07±1.56 mm CI 95% (16.9-23.23) measuring the posterior acoustic shadow width. Statistically significance differences were found between D2BW mean and D2US resulting in a size overestimation (3.8 mm) with ultrasound study (p=0.019). There were no statistically differences between D2BW and D2S. When analysed D2S mean, we found that D2S was nearer from the gold standard measure (D2BW) (p=0.52).
Ultrasound overestimated renal urolithiasic size compared to bone window CT (Gold Standard) (p<0.05) and the acoustic posterior shadow obtained more accuracy in measurements than ultrasound as statistically significant differences were no found.