Third prize: the impact of fluid environment manipulation on shockwave lithotripsy artificial calculi fragmentation rates

Assessing the Magnitude of Effect of Bone Structures on Shockwave Lithotripsy Fragmentation: Results from an In Vitro Study

INTRODUCTION

Several anatomic and clinical factors have been implicated in the failure rates of shock wave lithotripsy (SWL), including the attenuating effects of bony structures. We designed an in vitro model that incorporates the lumbar spine, including vertebral bodies and transverse processes along the pathway of shockwaves, to mimic the clinical scenario during SWL of upper ureteral stones. We hypothesized that the presence of bone structures in the SWL pathway significantly affects the fragmentation rate.

MATERIALS AND METHODS

An ordnance gelatin (OG) model was conceptualized and created to allow a pig's lumbar spine to be embedded within it. Artificial urinary calculi weighing 2 ± 0.1 g (1.2-cm diameter) were prepared using BegoStone plaster. The trial was divided into two arms: group 1 models had OG only and served as the control and group 2 models had the bone embedded in the gelatin with stone wells placed above the transverse processes. Twenty-four stones per group were subjected to SWL using the STORZ MODULITH SLX-F2 lithotripter, using the same treatment parameters. Fragments were sieved through 2- and 4-mm filters, and the fragmentation coefficients (FC) were calculated. The Mann-Whitney test was used to compare FC between the two groups.

RESULTS

The mean fragmentation rate of group 1 was statistically significantly higher compared with group 2 using a 4-mm sieve (43% vs 0.62%, p < 0.001) and the 2-mm filter (18% vs 0.52%, p < 0.001).

CONCLUSIONS

The presence of bone structures dramatically reduces the fragmentation rate of phantom stones using an OG in vitro model. The OG model is inexpensive and simple to use to simulate clinical situations during SWL.

The Effect of Renal Cysts on the Fragmentation of Renal Stones During Shockwave Lithotripsy: A Comparative In Vitro Study

PURPOSE

To assess the potential effect of simple renal cysts (SRC) on stone fragmentation during shockwave lithotripsy (SWL) in an in vitro model.

MATERIALS AND METHODS

The in vitro model was constructed using 10% ordnance gelatin (OG). Models were created to mimic four scenarios: Model A-with an air-filled cavity (suboptimal for stone fragmentation); model B-without a cavity (normal anatomy); model C-with a 3-cm serum filled cavity (to represent a small SRC); model D-with a 4-cm serum filled cavity (to represent a larger SRC). SWL was applied to 24 standardized phantom stones (weight of 2±0.1 g) in each model using a standardized protocol. Stone fragments were retrieved, then dried overnight at room air temperature. Fragmentation coefficient (FC) was calculated for each stone, for fragments<4 mm and <2 mm.

RESULTS

The OG in vitro model was robust enough for the proposed research. There was no fragmentation evident in model A as expected. The mean FC was 29.7 (±20.5) and 39.7 (±23.7) for <4 mm fragments (P=0.069) and 7.6 (±4.1) and 10.6 (±6.7) for <2 mm fragments (P=0.047), for noncystic and cystic models, respectively. The mean FC was 29.7 (±20.5), 38.8 (±26.2) and 40.7 (±21.3) for <4 mm fragments (P=0.213) and 7.6 (±4.1), 11.1 (±8) and 10.2 (±5.3) for <2 mm fragments (P=0.138), for models B, C, and D, respectively.

CONCLUSION

Our in vitro experiment confirms better stone fragmentation associated with SWL in the presence of adjacent SRC.

Extracorporeal lithotripsy endoscopically controlled by ureterorenoscopy (LECURS): a new concept for the treatment of kidney stones-first clinical experience using digital ureterorenoscopes

PURPOSE

To evaluate the feasibility and usefulness of extracorporeal lithotripsy endoscopically controlled by simultaneous flexible ureterorenoscopy (LECURS) and combined with Holmium laser lithotripsy for kidney stones surgery.

METHODS

Retrograde flexible ureteroscopy allowed stone visualization and intrarenal relocation when possible. Extracorporeal schock wave lithotripsy (ESWL) was performed under direct vision allowing constant focal zone adjustment for optimal stone fragmentation. Holmium laser lithotripsy was used simultaneously when necessary. Post-operative assessment included ultrasound at day one and abdominal CT scan 3 weeks later to evaluate for residual fragments.

RESULTS

Six patients with kidney stones were recruited including 3 with relative contraindication to ESWL. One patient had a stone beyond an infundibular stenosis and 2 had multiple stones in a horseshoe kidney with an uretero-pelvic junction (UPJ) stricture. A 100 % stone fragmentation rate was obtained. Post-operative ultrasound was normal in 5 patients and showed slight peri-renal infiltration in the other. One patient developed an obstructive pyelonephritis requiring antibiotics and changing a double J to a ureteral catheter. No other complications were noted. Three patients (50 %) were stone free after LECURS. Three patients underwent a second-look procedure for small (<3 mm) retained residual fragments. No damage was seen with the digital ureteroscopes, laser fibers or stone baskets.

CONCLUSIONS

This initial experience with LECURS has shown to be feasible and safe. This opens the opportunity for further evaluation of this approach in order to improve outcomes of both approaches.