Does Hounsfield Unit have any significance in predicting intra and postoperative outcomes in retrograde intrarenal surgery using holmium and Thulium fiber laser? A critical analysis of results from the FLEXible ureteroscopy Outcomes Registry (FLEXOR)

Abstract

The objective was to evaluate outcomes of retrograde renal surgery for intrarenal stones of any size, number, and position, comparing hard versus soft stones based on their attenuation on computed tomography (Hounsfield Unit-HU). Exclusion criteria; children/adolescents, ureteric stones, renal anomalies, or bilateral surgery. Patients were divided into two groups according to the type of laser employed, i.e. Holmium:YAG (HL) and Thulium fiber laser (TFL). Residual fragments (RF) were defined as > 2 mm. Multivariable logistic regression analysis was performed to evaluate factors associated with RF and RF needing further intervention. 4208 patients from 20 centers were included. 3070 patients were operated on with HL. In HU < 1000 stones, the TFL group had larger stones (11.56 ± 10.38 vs 9.98 ± 6.89 mm,p < 0.001). Multiple and lower pole stones were more prevalent in the HL group. Lasing time was shorter in the TFL group (15.34 ± 12.55 vs 23.32 ± 15.66 minutes,p < 0.001). HL group had a higher incidence of RF (29.1% vs 13.7%,p < 0.001). Age, stone size, and HL were predictors of RF, whereas multiple stones, and HL of RF requiring retreatment. In HU ≥ 1000 stones, stone size was similar between the two groups, whilst multiple and lower pole stones were more prevalent in the HL group. Surgical time was significantly shorter in the HL group (64.48 ± 33.92 vs 79.54 ± 88.56,p < 0.001). Significantly higher incidence of RF was noted in HL (22.7% vs 9.8%,p < 0.001), whilst reintervention rate was significantly higher TFL group (69.6% vs 43.8%,p < 0.001). Age, stone size, and use of HL were predictors of RF, whilst recurrent stone formers, multiple stones, and use of TFL of RF requiring retreatment.

Application of tip-bendable ureteral access sheath in flexible ureteroscopic lithotripsy: an initial experience of 224 cases

“…Third, the effect of stone density was also assessed. Houns eld density used to be an important parameter to predict the outcome of RIRS [20] . In our study, we assigned 1200 Hu as a speci c threshold to stratify the hardness into two categories.…”

Kidney Stone Classification Using Multimodal Multiphoton Microscopy

“…1 Extracorporeal shockwave lithotripsy is now supplanted by flexible ureteroscopy using thulium lasers, which are more efficient for reducing stones into a powder easily evacuated in urine. 9 KS are composed of multiple crystalline domains. Established methods for KS component characterization include optical microscopy, 1,10 Fourier transform IR spectroscopy, 1 Raman spectroscopy, 6,11−14 (SEM), 15 and X-ray crystallography.…”

Does unenhanced computerized tomography as imaging standard post-retrograde intrarenal surgery paradoxically reduce stone-free rate and increase additional treatment for residual fragments? Outcomes from 5395 patients in the FLEXOR study by the TOWER group

“…Many studies focus on several variables like demographic factors, 1 stone parameters, 2 and intraoperative technical steps and technology used 3 to predict stone-free rate (SFR) and outcomes of retrograde intrarenal surgery (RIRS) in adults and children alike. Similarly, preoperative computerized tomography (CT) imaging for endourological intervention is ideal for kidney stones and to estimate stone parameters like Hounsfield units (HU), 4 and its ability to influence decision-making for RIRS has been well documented.…”