Can Hounsfield Unit of Preoperative Non-Contrast Computed Tomography be used to Predict Calcium Urinary Stone Composition?
Pin-Chun Liu, Yi-Sheng Lin, Yen-Chuan Ou, Chao-Yu Hsu, Min-Che Tung
Division of Urology, Department of Surgery, Tungs’ Taichung Metroharbor Hospital, Taichung, Taiwan
Non-contrast computed tomography (NCCT) has been widely used as a diagnostic tool for acute flank pain patients. The composition of urinary stones has strong association with urolithiasis treatment strategies. This study is meant to evaluate whether the Hounsfield unit (HU) of non-contrast computed tomography could predict the composition of calcium urinary stone.
Materials and Methods:
We identified patients from single centers who had undergone urinary stone treatment between 2019 and 2021. The inclusion criteria were mineral stone analysis with calcium components (calcium oxalate stone and calcium phosphate) more than 75% and preoperative NCCT available. The average value of HU was obtained by built-in software of the medical image system (INFINITT healthcare.co). Stone diameters less than 5mm were excluded due to HU inaccuracies in analysis of smaller stones. HU density (ratio between HU and largest diameter of stone) was applied to eliminate the confounding factor between stone size and HU. A statistical comparison was made between HU value and HU density.
Total 953 patients were reviewed; 190 patients met our inclusion criteria. The composition of calcium stone contains calcium oxalate stone (n=163) and calcium phosphate stone (n=27). The median HU of calcium oxalate and calcium phosphate stone are 919 and 1037 respectively. Statistics revealed significant differences of HU between calcium oxalate stone and calcium phosphate stone (P=0.003). The cut off value for calcium oxalate HD is 968. Statistic tests revealed no differences between baseline characteristics such as age and gender.