5 YEARS EXPERIENCE IN EXPERIMENTAL LASER LITHOTRIPSY

In the first part of our experience approximately 300 stones of differ ent composition have been treated in vitro with three different laser sources: Nd-YAG laser (1,064 nm), dye laser (504 nm) and alexandrite l aser (755 nm). Calcium oxalate monohydrate and brushite stones appeare d to be the most resistent to lithotripsy. Highest fragmentation rates were obtained for clacium oxalate dihydrate stones followed by struvi te, uric acid and hydroxyapatite stones. The Nd-YAG laser did not appe ar to be ideal for lithotripsy since early damage to the fiber tip was observed when this source was used. Both the dye and the alexandrite lasers were almost always effective in fragmenting the various types o f stones. We subsequently treated some cystine stones while immersed i n water or in solutions of carmine indigo (2%), methylene blue (5%), r ifamycin (0.6 and 6%) and rifampicin (0.8 and 0.3%) with the dye or th e alexandrite laser. The spectra of these solutions, previously analyz ed with the spectrophotometer, showed that rifamycin and rifampicin ab sorbed large amounts of light radiation at the wave length of the dye laser (504 nm). Successful fragmentation occurred only when the dye la ser was used to treat stones immersed in the more concentrated solutio ns of these two substances. The quantity of fragmented material after treating a 10-cm3 cystine stone previously immersed in the more concen trated solutions of rifamycin and rifampicin (30 and 10 mm3, respectiv ely) confirmed previous results. The clinical use of rifamycin and rif ampicin as mediators of lasertripsy at 504 nm of hard or 'nonabsorbent ' stones is suggested since these substances seem to trigger plasma fo rmation at a low energy level on the surface of the stone that they co ated.