The irrigation flow used in PCNL creates a clear endoscopic view and contributes to flushing out residual fragments as shown by the vacuum cleaning effect recently described. We aimed to further analyze these processes using computerized models (CM) for prediction and a PCNL practical model (PM) to validate the calculations.
COMSOL Multiphysics® software was used to simulate the irrigation flows and the particles’ movements in a two-dimensional kidney model based on CT imaging graphically translated by CAD software. A similarly shaped model was constructed, and PCNL was simulated, while the movements of the particles were monitored by a high-speed digital camera (figure). Particle movement of both models was compared at various flow velocities and nephroscopic positions.
Results for various velocities at 90° and various angles at a velocity of 1 m/s are reported here.The numerical model predicted a significantly increased particle clearance with high-velocity irrigation (0.25 vs 1 m/s, 12% vs 70%: p<0.0001), as did the perpendicular instrument (45% vs 90%, 1% vs 70%: p<0.0001) compared to angled position. These results were validated in the practical model (table). This process occurred only in the directly irrigated calyx while clearance the flow and subsequently the particle movements in the other calices are null.
|Velocity (m/s) at 90°||CM Clearance at 120 sec (%)||PM Clearance at 120 sec (%)|| P value
[OR(90% confidence interval)]
|Instrument angle (°) at 1 m/s|
|1||70||80||0.14 [1.7 (0.89-3.2)]|
|90||70||80||0.14 [1.7 (0.89-3.2)]|
Clearance of particles are produced only when irrigation is perpendicularly directed to the targeted calyx and its effectiveness is enhanced at higher flow velocities. There is no effective flow in calyces that are not directly irrigated. The validation of the numerical calculated model in the practical model confirms that computerized software can be utilized for advanced renal hydrodynamic research and possibly reduce the number of studies performed in animals and humans.