Evaluation of the effect of Bernoulli maneuver on operative time during mini-percutaneous nephrolithotomy: A prospective randomized study

The impact of siphoning effect on renal pelvis pressure during ureteroscopy using an in vitro kidney and ureter model

PURPOSE

To experimentally measure renal pelvis pressure (PRP) in an ureteroscopic model when applying a simple hydrodynamic principle, the siphoning effect.

METHODS

A 9.5Fr disposable ureteroscope was inserted into a silicone kidney-ureter model with its tip positioned at the renal pelvis. Irrigation was delivered through the ureteroscope at 100 cm above the renal pelvis. A Y-shaped adapter was fitted onto the model's renal pelvis port, accommodating a pressure sensor and a 4 Fr ureteral access catheter (UAC) through each limb. The drainage flowrate through the UAC tip was measured for 60 s each run. The distal tip of the UAC was placed at various heights below or above the center of the renal pelvis to create a siphoning effect. All trials were performed in triplicate for two lengths of 4Fr UACs: 100 cm and 70 cm (modified from 100 cm).

RESULTS

PRP was linearly dependent on the height difference from the center of the renal pelvis to the UAC tip for both tested UAC lengths. In our experimental setting, PRP can be reduced by 10 cmH20 simply by lowering the distal tip of a 4 Fr 70 cm UAC positioned alongside the ureteroscope by 19.7 cm. When using a 4 Fr 100 cm UAC, PRP can drop 10 cmH20 by lowering the distal tip of the UAC 23.3 cm below the level of the renal pelvis.

CONCLUSION

Implementing the siphoning effect for managing PRP during ureteroscopy could potentially enhance safety and effectiveness.

Impact of Renal Access Angle and Speed of Nephroscope Retrieval Movements on the Vortex Effect

OBJECTIVE

To analyze the influence of different renal access angles (AAs) and nephroscope retrieval speeds on the efficacy of the vortex effect (VE) in mini-percutaneous nephrolithotomy (mini-PCNL). This study aimed to understand the poorly understood physical components of the VE.

MATERIALS AND METHODS

A Pexiglas™ (KUS®) model was built based on the dimensions of a 15/16 F mini-PCNL set (Karl Storz). The flow rate was continuous via an automatic pump and calibrated to achieve hydrodynamic equivalence to the real equipment. One experiment consisted of manually retrieving all 30 stone phantoms (3 mm diameter) utilizing only the VE. Cumulative time to retrieve all stones was measured. An accelerometer recorded instant speeds of the nephroscope every 0.08 seconds (s), and 3 experiments were performed at each angle (0°, 45°, and 90°). A logistic regression model was built utilizing maximum speeds and access angles to predict the effectiveness of the VE.

RESULTS

Mean cumulative time for complete stone retrieval was 28.1 seconds at 0° vs 116.5 seconds at 45° vs 101.4 seconds at 90° (P < .01). We noted significantly higher speeds at 0° compared to 45° and 90° (P < .01); however, differences in average and maximum speed between 45° and 90° were not statistically significant (P = .21 and P = .25, respectively). The regression model demonstrated a negative association between increasing maximum speed and VE's effectiveness (OR 0.547, CI 95% 0.350-0.855, P < .01). When controlling for maximum speed, the 0° angle had significantly higher chances of achieving at least a partially effective VE.

CONCLUSION

Increasing the renal access angle or nephroscope extraction speed negatively impacts the effectiveness of the VE. This significantly increased procedure time in the laboratory model, suggesting that the VE is less effective at higher sheath angles.

Optimizing stone harvesting in miniaturized-PCNL: a critical examination of renal access angles, technology, and the role they play in operative efficiency

PURPOSE

Stone retrieval can be a laborious aspect of percutaneous nephrolithotomy (PCNL). A unique phenomenon of mini-PCNL is the vortex-effect (VE), a hydrodynamic form of stone retrieval. Additionally, the vacuum-assisted sheath (VAS) was recently developed as a new tool for stone extraction. The purpose of our study is to investigate the impact of renal access angle (as a surrogate for patient positioning) on stone retrieval efficiency and compare the efficiency among methods of stone retrieval.

METHODS

A kidney model was filled with 3 mm artificial stones. Access to the mid-calyx was obtained using a 15Fr sheath. Stones were retrieved over three minutes at angles of 0°, 25°, and 75° utilizing the VE, VAS, and basket. Stones were weighed for comparison of stones/retraction and stones/minute. Trials were repeated three times at each angle.

RESULTS

Renal access angle of 0° was associated with increased stone retrieval for both the VE and VAS (p < 0.05). The VE was the most effective method for stones retrieved per individual retraction at an angle of 0° (p < 0.005), although when analyzed as stones retrieved per minute, the VE and VAS were no longer statistically different (p = 0.08). At 75°, none of the methods were statistically different, regardless if analyzed as stones per retraction or per minute (p = 0.20-0.40).

CONCLUSIONS

Renal access angle of 0° is more efficient for stone retrieval than a steep upward angle. There is no difference in stone retrieval efficiency between the VE and VAS methods, although both are superior to the basket at lower sheath angles.

Precision Stone Surgery: Current Status of Miniaturized Percutaneous Nephrolithotomy

PURPOSE OF REVIEW

Innovations in lasers and surgical technology have led to a renewed interest in the miniaturization of percutaneous nephrolithotomy (PCNL). We review the different approaches and evidence on the efficacy of mini-PCNL.

RECENT FINDINGS

Mini-PCNL encompasses a range of techniques using tract sizes from 4.8 to 22 F to treat renal stones. The most common device uses irrigation to passively extract stones out of the sheath. Super-mini-PCNL incorporates active suction. Ultra- and micro-techniques reduce the tract to smaller diameters. Laser fragmentation is the main lithotripsy modality. Studies demonstrate an association with reduced complications, hospital stay, and increased tubeless rate. Drawbacks include longer operative times while stone-free rates for larger stones may be sub-optimal. Mini-PCNL has advantages of less trauma and the avoidance of nephrostomy tubes. Ambulatory surgery is feasible in select patients. Advances in laser lithotripsy and active suction have the potential to improve stone clearance and treat larger stones.