Holmium:YAG Percutaneous Nephrolithotomy: The Laser Incident Angle Matters
Teichman J, Rao R, Glickman R and Harris M

PURPOSE: Laser physics dictate that maximal radiant exposure occurs when the laser strikes the target at a normal incidence. Since the renal collecting system often limits nephroscope movements during percutaneous nephrolithotomy, the laser-calculus incidence angle may vary. We have observed during holmium:YAG percutaneous nephrolithotomy that the side firing fiber more easily approaches a normal incidence compared to the end firing fiber. We test the hypothesis that holmium:YAG percutaneous nephrolithotomy is faster with a side firing fiber compared to an end firing fiber.

MATERIALS AND METHODS: Consecutive holmium:YAG percutaneous nephrolithotomy cases were studied retrospectively. The calculus size and composition, surgical time, fragmentation speed (size/time) and stone-free rates were compared between 11 patients treated with end and 8 treated with side firing fibers.

RESULTS: When the end and side firing groups were compared, calculus sizes (mean plus or minus standard deviation) were 22 +/- 13 versus 48 +/- 17 mm. (p= 0.004) calcium oxalate monohydrate incidence was 55 versus 75% (p= 0.3), surgical times were 168 +/- 87 versus 124 +/- 51 minutes, computed fragmentation speeds were 0.15 :+/-0.09 versus 0.43 +/- 0.15 mm. per minute (p= 0.0009) and stone free rates were 73 versus 88% (p= 0.4), respectively.

CONCLUSIONS: The side firing fiber is faster than the end firing fiber for holmium:YAG percutaneous nephrolithotomy. These results are consistent with principles of laser physics.

Journal of Urology, Vol. 159, Number 3, 690-694, Mar 1998

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