PURPOSE: To analyze dual energy stone parameters performed preoperatively in correlation with the total Laser energy used in the fragmentation of urinary stones during retrograde intrarenal surgery (RIRS).
MATERIALS AND METHODS: This is a retrospective study of 17 patients (5 Females and 12 males) with a mean age of 49,31 ± 13,2 years that underwent RIRS from 7/2017 to 4/2018. A non-contrast Dual Energy Computed Tomography (IQON, Philips Healthcare, Cleveland, OH) of the abdomen was performed to all patients. The stone characteristics that were evaluated included stone number, location, stone burden (volume) and Hounsfield Units(HU). DECT parameters included effective Z number as well as analysis to calcium/uric acid based on the vendor software. The main intraoperative characteristics included procedure time and Total Laser Energy used during the fragmentation of the stones
RESULTS: A total of 19 stones were treated (15 calcium and 4 uric acid). The mean stone burden (volume) was 675,94 ± 893,41 mm3 . The mean maximum diameter of the stones 10,77 ± 5,32 mm (range 4 to 21 mm). The mean HU of the stones was 1060,47 ± 414,15. The effective Z range was 7.74-12.41 with a mean of 9.2. The mean total Laser energy used during the fragmentation was 4597,05± 3882,27 Joules. Larger stones needed more energy deposition (p<0.01). Average HU did not correlate with energy deposition as well as effective Z and type of stone.
CONCLUSIONS: Stone size is correlated with the energy needed for fragmentation. DECT parameters, as well as HU, do not correlate with energy deposition. Preoperative analysis of stone composition may not be effective in predicting laser energy deposition during surgery.
