Stone-breaking and retrieval strategy during retrograde intrarenal surgery

Optimal placement of flexible ureteral access sheath in retrograde intrarenal surgery

This study aims to explore the optimal location of flexible ureteral access sheath (f-UAS) in retrograde intrarenal lithotripsy (RIRS). RIRS model was built by AutoCAD 2011 software, and imported COMSOL 5.6 software to computer simulation. An RIRS model was constructed in vitro to analyze the distribution pattern of stone fragments and compare the weight of stone fragments carried out by the irrigation fluid when the f-UAS is in different positions. Computer simulation showed that the highest flow of irrigation fluid was in the channel of flexible ureteroscopy (f-URS) and in the lumen of f-UAS. From the f-URS to the renal collection system and then to the f-UAS, the velocity of irrigation fluid changes gradually from high-flow to low-flow and then to high-flow. When the f-URS and the f-UAS are at the same level, the irrigation fluid is always at a state of high flow during the process from f-URS to f-UAS. When the f-URS and the f-UAS are at the same level, it can increase the local intrarenal pressure (IRP) at the front of f-URS. The stone fragments are mainly sediment in the low-flow region of irrigation fluid. More stone fragments could follow the irrigation fluid out of the body when the tip of f-URS and the tip of f-UAS are at the same level (P < 0.001). The f-UAS should be brought closer to the stone in RIRS. And more stone fragments can be taken out of the body by the effect of irrigation fluid.

The Feasibility of Pop-Dusting Using High-Power Laser (2 J × 50 Hz) in Retrograde Intrarenal Surgery for Renal Stones: Retrospective Single-Center Experience

Objective: Recently, retrograde intrarenal surgery (RIRS) using laser lithotripsy has become popular. However, the optimal laser energy setting for pop-dusting has not been established. In this study, we report our experiences of RIRS using the high-power (up to 100 W) pop-dusting (HPPD) technique. Methods: This study retrospectively assessed 82 cases with RIRS using HPPD. Patients who underwent abdominal CT or mercaptoacetyltriglycine (MAG3) diuretic renal scan at 3 months postoperatively were included in this study. Patient and stone characteristics and perioperative and postoperative outcomes were evaluated. Results: The average number of renal stones was 3.67 ± 4.11, and the average length of the largest stones was 13.30 ± 6.41 mm. The mean Hounsfield units was 959.99 ± 384.73. The operation time was 58.10 ± 26.67 minutes. The mean HPPD time was 11.93 ± 9.48 minutes, with settings of 1.97 ± 0.25 J and 48.78 ± 3.29 Hz. The stone-free rate was 89%. The mean hospital stay was 1.68 ± 1.29 days. Pelvicaliceal and ureter injuries were observed in 9.8% and 32.9% of the study population, respectively. However, there was no transfusion, subcapsular hematoma, persistent urinary leakage, ureteral or infundibular stricture, or renal functional deterioration. There was transient postoperative fever in 12.2% of the study population. Conclusions: HPPD could be performed safely during RIRS for renal stones without significant complications such as collecting system injury or bleeding. High-power laser mode (up to 100 W) can be a safe and effective choice for pop-dusting during RIRS, especially for large and hard stones.

Stone heterogeneity index on single-energy noncontrast computed tomography can be a positive predictor of urinary stone composition

The aim of this study was to investigate the correlation between stone composition and single-energy noncontrast computed tomography (NCCT) parameters, including stone heterogeneity index (SHI) and mean stone density (MSD), in patients with urinary calculi. We retrospectively reviewed medical records of 255 patients who underwent operations or procedures for urinary stones or had spontaneous stone passage between December 2014 and October 2015. Among these, 214 patients with urinary calculi who underwent NCCT and stone composition analyses were included in the study. Maximal stone length (MSL), mean stone density (MSD), and stone heterogeneity index (SHI) were determined on pretreatment NCCT. The mean MSD (454.68±177.80 HU) and SHI (115.82±96.31 HU) of uric acid stones were lower than those of all other types. Based on post hoc tests, MSD was lower for uric acid stones than for the other types (vs. CaOx: P<0.001; vs. infection stones: P<0.001). SHI was lower for uric acid stones than for the other types (vs. CaOx: P<0.001; vs. infection stones: P<0.001) Receiver operating characteristic curves of uric acid stones for MSD and SHI demonstrated that SHI (cut-off value: 140.4 HU) was superior to MSD (cut-off value: 572.3 HU) in predicting uric acid stones (P<0.001).

Systematic review and meta-analysis to compare success rates of retrograde intrarenal surgery versus percutaneous nephrolithotomy for renal stones >2 cm: An update

BACKGROUND

We performed a systematic review and meta-analysis comparing stone-free rates between retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PCNL), using updated, more reliable evidence.

MATERIALS AND METHODS

Randomized controlled trials comparing RIRS and PCNL for >2 cm stones were identified from electronic databases. Stone-free rates for the procedures were compared by qualitative and quantitative syntheses (meta-analyses). Outcome variables are shown as risk ratios (RRs) with 95% confidence intervals (CIs).

RESULTS

Eleven articles were included in this study. Most recently published studies exhibited relatively low quality during quality assessment. For the meta-analysis comparing success (stone-free) rates between PCNL and RIRS, the forest plot using the random-effects model showed an RR of 1.11 (95% CI 1.02-1.21, P < .014) favoring PCNL. After determining the among-study heterogeneity, subgroup analysis was performed of 9 studies with less heterogeneity: the stone-free rate of PCNL was superior to that of RIRS using a fixed-effect model (RR 1.07, 95% CI 1.01-1.14, P < .019) for these studies.

CONCLUSIONS

RIRS can be a safe and effective procedure for selected patients with large renal stones. However, in this meta-analysis, the postoperative stone-free rate of PCNL was higher than that of RIRS in patients with >2 cm renal stones.