New device for visual neodymium:YAG laser prostate ablation: Acute and chronic canine evaluation

This canine study (n = 6) evaluated the acute and chronic effects of Nd:YAG laser prostatectomy using a Prolase II fiber. The Prolase II device consists of a 1,000 μm quartz fiber which directs a cone of Nd:YAG laser energy, at 45° to the axis of the fiber, into the prostatic urethra under direct visual guidance [visual laser ablation of prostate, (VLAP)]. Under visual guidance and saline irrigation, 60 seconds of 60 watts of laser power was delivered at 3, 6, 9, and 12 o'clock positions (14,400 J). One canine was instrumented but received no laser energy (control). One prostate was harvested acutely. The remaining four laser‐treated dogs were evaluated at 6 to 16 weeks. The histopathology of acute laser effects shows areas of necrosis with loss of glandular structures and stromal edema. Surrounding this area was a zone of degenerative glandular structures extending up to 12.6 mm into the prostate. Two of the four dogs developed urinary retention at 6.5 and 9 weeks. On examination, both were found to have fibrotic strictures at the distal prostatic urethra with markedly dilated proximal prostatic urethral lumens (1.98 and 2.8 cm). Two other dogs showed no signs of urinary retention at sacrifice. Histopathology, both the 6 and 16 week laser‐treated animals without urinary retention demonstrated dilated prostatic urethras with maximum cross‐sectional diameters of 1.52 and 1.50 cm, respectively. However, the 16 week dog demonstrated mild distal urethral narrowing by urethrogram. The control dog demonstrated normal histology of the prostate at 16 weeks. This study demonstrates the safety and initial results of a delivery device for trans‐urethral laser prostate ablation in a canine model. Further studies are needed to evaluate the cause of the fibrotic urethral strictures in this model and determine its clinical relevance. © 1994 Wiley‐Liss, Inc.