PD05-10: Characterization of mixed urinary stone composition with dual-source dual-energy computed tomography in vivo compared with infrared spectroscopy

Xianghu Meng*, Xueying Sun, Rong Cong, Liang Qi, Zengjun Wang, Rijin Song, Nanjing, China, People's Republic of

Introduction: Most studies have demonstrated the possibility of using dual-source dual-energy computed tomography (DSDECT) to distinguish pure stones with high accuracy. However, stones are frequently formed from a mixture of substances, and few studies have focused on mixed stones. The aim of the study was to retrospectively evaluate the diagnostic accuracy of DSDECT for predicting the composition of mixed urinary calculi in vivo compared with postoperative infrared spectroscopy (IRS) stone analysis.

Methods: We retrospectively included 111 patients with 117 mixed urinary stones diagnosed by IRS who underwent DSDECT between June 2018 and March 2020. Patients diagnosed with urolithiasis were examined by DSDECT preoperatively. The final stone composition was detected by IRS in vitro postoperatively. Then stone composition predicted from DSDECT was compared to IRS results which were known as the reference standard.

Results: According to the results determined by IRS, 117 mixed urinary calculi which were composed of a main constituent and minor admixtures included in this study were divided into four groups: calcium oxalate (CaOx)-hydroxyapatite (HA) (n=70), HA-CaOx (n=36), uric acid (UA)-CaOx (n=8), cystine (CYS)-HA (n=3). The accuracy of DSDECT for predicting all components of mixed urinary stones were 68.4%, 64.1%, 97.4%, and 97.5% for CaOx-HA, HA-CaOx, UA-CaOx, and CYS-HA stones, respectively. Imaging characteristics of different mixed urinary stones scanned by DSDECT showed that ratio of CaOx-HA was lower than HA-CaOx (1.59±0.11 vs 1.66±0.22, P<0.05). Meanwhile, CT values of CaOx-HA under 150 kV were higher than those of HA-CaOx (915.41±226.84 vs 799.56±252.01, P<0.05).

Conclusions: Although DSDECT has a relatively low accuracy for predicting components of CaOx-HA and HA-CaOx in vivo, combining with ratio and CT values may help to differentiate these stones.

Source of Funding: None