Yes! They do it standing!!
http://www.thehorse.com/articles/10348/cryptorchid-surgery
Laparoscopic cryptorchidectomies can be performed either with the horse standing or under general anesthesia. With standing laparoscopic cryptorchidectomies, the horse is sedated and local anesthesia is used to desensitize the skin where the camera will be introduced. General anesthesia is not necessary for this approach. In standing approaches, the camera is placed through the horse’s flank. The caudal abdomen then can be explored to see if a retained testicle is present within the abdomen. Once identified, the testicle is grasped, cut, and subsequently removed from the abdomen. In cases of unilateral cryptorchids, after removal of the retained testicle, the descended testicle is removed through a standing castration, or the horse is anesthetized and the descended testicle is removed routinely.
I haven’t any experience with and obviously didn’t even know it was happening. And am wondering if there are people here with more familiarity.