ABSTRACT
BACKGROUND AND PURPOSE: Studies have suggested that shockwave lithotripsy (SWL) stone fragmentation rates can be affected by characteristics of the fluid media surrounding the stone, although evidence to implicate the impact of urine specific gravity (SG) is limited and inconclusive. Our aim is to further explore the impact fluid media and SGs have on stone fragmentation using a variable focus lithotripter. MATERIALS AND METHODS: Artificial stones were presoaked for 24 hours in urine and then shocked in various fluid media including artificial urine (SG 1.010 control, 1.020, and 1.07), human pooled urine (HPU), degassed HPU, Pentastarch, 100% and 30% contrast, degassed 30% contrast, 100% ethanol, deionized water (dH(2)O), degassed dH(2)O, 5% glucose, Ringer lactate, 0.9% saline, glycerol, whole blood, and lubricating gel. After soaking, SWL using the Modulith SLX-F2 electromagnetic lithotripter was performed. Fragments were dried and sieved using a 4-mm diameter opening grid. Fragments >4 mm were weighed and fragmentation coefficients (FCs) calculated (pre-SWL weight - post-SWL weight)/(pre-SWL weight) × 100. Fifteen stones were shocked for each fluid group. RESULTS: Fluid type, viscosity, and degassing all significantly impacted stone fragmentation. While the solutions' SG, per se, did not appear to affect stone fragmentation, the use of degassed 30% contrast significantly improved stone destruction over the SG 1.010 artificial urine control (95.3% vs 71.4, P < 0.01). Furthermore, degassing improved comminution rates by increasing the number of completely fragmented stones (FC = 100%). Using degassed 30% contrast, 12/15 stones were completely fragmented, compared with only 2/15 in the control group (P = 0.007). Among the whole blood, glycerol, and lubricating gel groups, only 1/15, 0/15, and 1/15 stones reached 100% FC respectively in the narrow focus, possibly because of the detrimental impact of increased viscosity. CONCLUSIONS: Different fluid media can significantly affect FC in vitro. Among the various fluids tested, degassed 30% contrast significantly increased the FC and total number of completely fragmented stones.
