High intensity focused ultrasound ablation of the vas deferens in a canine model

High intensity focused ultrasound is an ablative technology capable of producing thermal coagulative necrosis of sub-surface structures without injuring intervening tissues. We assessed the feasibility of using high intensity focused ultrasound to produce occlusion of the canine vas deferens.

A high intensity focused ultrasound transducer was incorporated into a hand held clip specially designed to grasp the vas deferens transcutaneously. Slots within the jaws of the clip ensured that the vas deferens and high intensity focused ultrasound target zone were properly co-located. We ablated 10 vasa using a range of power and time parameters. At 2 weeks after ablation each vas, epididymis and testis was surgically harvested en bloc. Retrograde vasography was performed to assess vasal occlusion, followed by pathological analysis.

High intensity focused ultrasound occlusion of the vas deferens was confirmed in 4 specimens ablated with parameters at the upper end of the parameter range, 2 of the 2 ablated with 7 W. for 60 seconds and 2 of the 4 ablated with 7 W. for 30 seconds. Histological injury was noted in 8 of the 10 ablated specimens. Skin burns that developed over 4 of the targeted vasa were conservatively managed. Bilateral sham procedures in a control dog resulted in patent vasa and no associated skin burns.

We demonstrated the feasibility of noninvasive, transcutaneous high intensity focused ultrasound occlusion of the vas deferens with ablation powers at the upper end of the tested range, that is 7 W. Modifications of the hand held clip and optimization of ablation parameters would likely improve the success rate of this procedure. Refinement of this technology may provide a rapid noninvasive alternative to conventional vasectomy.