The effect of fat, muscle, and kidney on stone fragmentation by shockwave lithotripsy: an in vitro study.

BACKGROUND: Skin-to-stone distance (SSD) has been shown to influence the outcome of shockwave lithotripsy. SSD is composed of different tissues, including the subcutaneous fat, abdominal muscles, and renal tissue. The aim of this in vitro study was to investigate the effectiveness of extracorporeal shockwaves to fragment standard stones after passing through these tissue media. METHODS: Standard stones (Dornier's artificial model stones) were exposed to similar-intensity shockwaves that had to pass through different media before fragmenting the stones. The media that were placed in a special container between the stones and the lithotripter head included saline (n = 5), pure liquid animal fat (n = 6) and animal fatty tissue (n = 6), muscle (n = 6), and kidney tissue (n = 6). The number of shockwaves and energy required to completely fragment the stones were measured. RESULTS: There was no significant difference in the number of shockwaves required to completely fragment the stones when using pure liquid animal fat, animal fatty tissue, muscle tissue, or kidney tissue (19,908 +/- 3447; 21,255 +/- 4051; 22,845 +/- 3964; and 19,648 +/- 3691, respectively). However, when saline was used, the number of shockwaves was lower than in the other four media (5866 +/- 1018, p < 0.001 for all the media). The total energy required in each medium followed the same trend. CONCLUSIONS: The findings of this study indicated that the shockwaves had the same effectiveness in fragmenting stones whether they pass through the fatty or nonfatty tissues (muscle and kidney) that compose the SSD.