Comparing elective neutering techniques (Proceedings)
Castration techniques for exotic mammals include scrotal, prescrotal and abdominal surgical approaches. Some of these can be further classified as open or closed. Technique depends on the anatomy of the patient, and in many cases, is largely surgeon preference. Familiarity with alternatives will allow the surgeon flexibility to select the most appropriate technique when faced with an unfamiliar species or an anatomical peculiarity.
FerretFew veterinarians in the US castrate male ferrets, as the majority arrive in the pet store already neutered. The urogenital anatomy of the male ferret is similar to that of canids, with the penis situated cranial to the scrotal sac, which is anatomically more similar to that of domestic felids. Both scrotal and prescrotal techniques are described with the use of suture, hemostatic clips or even "self-tying" the vas deferens to the vessels. In the scrotal approach, the incisions are sutured or eft to heal without suture while the prescrotal skin and subcutaneous incision is sutured with 4-0 or 5-0 absorbable suture.
The urogenital anatomy of male rabbits is unique among placental mammal species but common in marsupial species. The penis is located caudal to the testicles, which lie cranial to the penis in two separate hemiscrotal sacs. Another very important anatomical peculiarity, similar to rodent species, is that he inguinal canal remains open throughout life, and the testicles are free to move from the hemiscrotal sacs to the abdominal cavity. Position of the testicles depends on many factors including body position, body temperature, breeding activity, gastrointestinal tract filling, and the amount of abdominal fat. The testicles are oval shaped. The epididymis is clearly visible at the caudal pole of the testicle, but not as developed as in rodent species. There is fat surrounding the testicles, but much less than in rodent species. The glans of the penis is not well developed, is point shaped and covered by a prepuce.
The two main anatomical peculiarities of male rabbits have important implications in regard to surgical techniques. The open inguinal canal is breached during surgery, and must be closed in order to prevent open communication between the hemiscrotal sac and the abdominal cavity, and potential herniation of abdominal viscera (intestine, bladder) into the hemiscrotal sac. The position of the penis caudal to testicles allows the surgeon to choose a prescrotal approach via a single incision on the midline as an alternative to a scrotal approach.
Elective castration in the rabbit is indicated for prevention of pregnancy, and reduction of urine spraying, social aggression and unwanted sexual behavior. It should be kept in mind that many owners maintain single intact male rabbits that do not exhibit undesirable behaviors. Therapeutic castration is indicated in cases of testicular disease including infection and neoplasia, and for correction of inguinal herniation and true cryptorchidism.
The rabbit is placed in dorsal recumbency under general anesthesia, and the prescrotal area shaved. For this technique, it is not necessary to attempt to shave and prepare the thin, delicate skin of the hemiscrotal sac. The surgical site is prepared for surgery. A 1.5-2 cm skin incision is made on the midline, just cranial to the base of the hemiscrotal sacs. Blunt dissection of the subcutaneous tissue, fat, and inguinal fascia reveals the vaginal processes caudal to where they enter the abdomen through the inguinal canal. In mature rabbits with abundant subcutaneous fat, identifying the vaginal processes may be slightly difficult. The surgeon can easily identify these by gently massaging the testicles back and forth from the hemiscrotal sac to the abdomen and visually identifying them as they pass through the thin vaginal processes. The vaginal process is bluntly dissected from surrounding soft tissues and isolated.
At this point, the procedure is continued by opening the vaginal process, or leaving it closed, thus proceeding as an "open" or "closed" technique. In the open technique, the vaginal process is exteriorized and 3-0 to 4-0 absorbable suture material passed around it and tied loosely or secured with a hemostat. The vaginal process is incised with blunt scissors to prevent iatrogenic damage to the vessels of the spermatic cord. The testicle is exteriorized through the incision, and the spermatic cord and vessels sutured. The remaining suture used to pass around the vaginal process is tied securely proximal to the incision in order to close the vaginal process. The procedure is repeated on the contralateral vaginal process, and skin incision closed routinely.