Exotic small mammal elective surgery (Proceedings)

Rabbit Ovariohysterectomy

Rabbits should be spayed anytime after 5 months of age. When very young, the uterine horns and ovaries are very tiny making identification challenging. However, in older mature and perhaps overweight rabbits, the mesometrium is extremely fatty and friable. OVH is indicated in all female rabbits to prevent pregnancy, control territorial aggression, prevent uterine neoplasia (80% incidence), or other uterine disorders such as pyometra. Unique anatomy for the rabbit is their bicornuate cervix, long convoluted and fragile fallopian tube, and a flaccid vaginal body that will fill with urine during micturition, and a very large amount of fat is common in the region of the broad ligament and suspensory ligament (making it difficult to ID the ovarian and uterine vessels)

        Surgical Technique

A 2-3cm midline incision is made approx. half way between the umbilicus and the pubic symphysis. The linea is identified and grasped and greatly elevated with thumb forceps as a stab incision is made into the abdomen. Great care is taken when entering the abdomen as the very large and very thin walled cecum and urinary bladder often lay directly against the ventral abdominal wall. The GI tract should be minimally handled to minimize the likelihood of post op adhesions. A spay hook is not necessary as the uterus is easily visible and can be gently lifted through the incision using fingers or forceps. The uterus is followed to the oviduct and infindibulum. These may be embedded in fat and gentle digital manipulation and traction will allow for identification of the ovary and its vasculature. .The ovarian vessels are double ligated using PDS or Monocryl suture. The procedure is repeated for the opposite ovary. The uterus and its vessels are identified. The vessels are double ligated separate from the uterine body. The uterus can then be ligated cranial or caudal to the cervices. Closure of the abdomen with a 4-0 or 3-0 monofilament absorbable suture is routine. Simple continuous or interrupted in the linea followed by simple continuous pattern in SQ/intradermal.

Rabbit Castration

Rabbits should be castrated to control urine marking behaviors, prevent reproduction, control and minimize territorial aggression, and avoid chance of testicular tumors.

        Surgical Technique:

Both prescrotal and scrotal techniques have been described. The scrotal technique is very similar to the cat. Complication of scrotal edema and hematoma is reported. An incision is made in the scrotum in a non-vascular region being careful to not incise the vaginal tunic. A hemostat is used to help separate/free the testicle from the scrotum and the testicle with gentle pressure is manipulated out of the incision. The caudal ligament of the testicle is torn from its scrotal attachment, completely freeing the testicle and spermatic cord. The spermatic cord is clamped distal to the testicle and close to the inguinal ring. The spermatic cord is double ligated using 4-0 absorbable suture and then resected. The scrotal skin is apposed using tissue glue. The procedure is repeated for the opposite testicle. For the prescrotal technique a 1.5cm incision is made on the midline just cranial to the scrotum similar to a akin incision for a canine castration. One of the testicles is manipulated toward the incision by applying gently digital pressure on the scrotum. It the testicle is withdrawn into the abdomen, gentle pressure is applied to the abdomen to return testicles to their normal position. The fat is dissected away with hemostats to expose and isolate the vaginal tunic. The vaginal tunic is lifted up and the caudal ligament of the testicle is carefully torn from its scrotal attachment, freeing the testicle and spermatic cord. The spermatic cord is clamped distal to the testicle and close to the inguinal ring. The spermatic cord is double ligated using 4-0 absorbable suture and then resected. The procedure is repeated for the opposite testicle. The subQ tissue is closed with a simple continuous pattern followed by a continuous intradermal skin closure.

Guinea Pig Ovariohysterectomy

Female guinea pigs have a high perinatal mortality rate. Still births and dystocias are related to large fetuses, subclinical ketosis, and fusion of the pubic symphysis due to ossification that occurs after 6 months of age. 76% of female guinea pigs btw 2-4 years will develop ovarian cysts spontaneously which are painful and can be fatal. Neoplasia and pyometra are uncommon but can occur.

        Surgical Technique

The guinea pig OVH is very similar to the rabbit with 2 exceptions:

1. the ovaries are supported by a short mesovarium making the ovary more difficult to exterorize than rabbits. An extended incision cranially may be necessary to avoid tearing of the fragile and fatty suspensory ligament. Hemoclips vs. suture may make ligation and removal of the ovarian pedicle easier.

2. It is recommended to ligate the uterus just cranial to the cervix.

Guinea Pig Castration

Castration is recommended mostly to control reproduction and related objectionable behavior. However it is also indicated with neoplasia and trauma. It may also be beneficial in decreasing the amount of oil secretion from the rump sebaceous gland which is testosterone stimulated. It is important to remember that guinea pigs have large epididymal fat pads within the vaginal tunic that prevent intestinal herniation.

        Surgical Technique

Can be performed open or closed. The closed technique is recommended. The testicles are removed through separate 1-2 cm incisions made in the center over each scrotum parallel to the penis. Care is taken not to penetrate the vaginal tunic. If inadvertent incision into the tunic occus while incising over the scrotum making it "open", then the tunic surrounding the spermatic cord and vas deferens can be grasped more proximally and still double ligate in a closed fashion. Grasp the tunic and remove the testicle from the scrotum and gently dissect the tunic from its attachment circumferentially. When isolated, apply gentle traction and strip the fascial attachments using gauze. Now the testicle can be exteriorized and the spermatic cord isolated proximally. Double ligate using absorbable suture material close to the inguinal ring. It is not necessary to remove the epididymal fat pad as leaving it may prevent herniation. Repeat on the opposite testicle. Several SQ and/or intradermal sutures are place in each scrotum.

Rat Ovariohysterectomy or Ovariectomy

It is advisable to perform either a OVH or ovariectomy on female rats to decrease the incidence of mammary tumors from 50% to less than 5%. It has been shown effective even at the time of a mammary tumor removal to decrease the risk of reoccurrence.

        Surgical Technique

A traditional ventral midline approach is preferred for OVH. A midline incision is made through the skin from just posterior to the umbilicus to just cranial to the rim of the pubis. The linea, which is very thin, is identified and incised to enter the abdomen. The intestines are gently manipulated aside with a moistened sterile cotton swab. The cotton swab is used to elevate the uterus and isolate the repro tract. It is not uncommon for the abdomen of rats to be abundant with fat regardless of the size of the rat. The ovarian vasculature is ligated using appropriate sized hemoclip. The process is repeated on the opposite side. The junction of the uterine horns and cervix is located, elevated and double ligated using hemoclip or 4-0 absorbable monofilament suture. The abdominal wall is sutured in a simple continuous pattern followed by a simple continuous intradermal closure of the skin. The ovariectomy is performed through a flank technique. An approx. 1.5cm incision is made in the right flank just caudal to the last rib and ventral to the lumbar muscle. The muscle is exposed and a blunt hemostat is used to puncture through the muscle into the abdominal cavity. The ovary is located within a bundle of fat at the area of the incision and is gently exteriorized. The ovarian vasculature and uterine horn are double ligated using a 4-0 absorbable monofilament suture. The muscle is closed using a cruciate suture pattern or simple interrupted. The skin is closed with an intradermal pattern followed by tissue glue. The same procedure is repeated on the opposite side.

Ferret Castration

While most ferrets are acquired from the pet store and have already been spayed/neutered and descented. Those acquired from individual breeders should be castrated in attempt to decrease odor, unwanted reproduction and unwanted associated behaviors.

        Surgical Technique:

Castration in the ferret can be done prescrotal like in the dog or scrotal like in the cat. One prescrotal incision is made, Either closed or open technique can be used. The spermatic cord, vessels, and associated tunics are double ligated using 4-0 absorbable suture and removed. This skin is closed using the same absorbable suture. Scrotal castration involves 2 incisions in the scrotum, exposing the testicle and associated vasculature and spermatic cord. These are double ligated and removed. The scrotal incision is left open like in the cat castration.

Ferret Ovariohysterectomy

Female ferrets should be spayed by the time they are 6 months old if they are not intended for breeding. Ferrets are induced ovulators, and when estrogen levels remain high for a long time, it can lead to potentially fatal bone marrow suppression.

        Surgical Technique

This surgical technique is very similar to a cat OVH. A 2-3cm incision is made on the ventral midline, starting at about 1-2cm from the umbilicus and extending caudally. The linea alba can be easily identified after dissecting through the subcutaneous fat and is incised. The ferret uterus is bicornuate and has a uterine body. The uterus is identified and the ovarian tissue then located. There can be an abundant amount of fat around the ovarian and uterine vessels so careful and blunt dissection is necessary. The ovarian vessels are double ligated using 3-0 absorbable monofilament suture. The same is repeated for the opposite ovary. The uterine body is then double ligated and removed. The abdominal wall is closed using 3-0 or 4-0 absorbable monofilament suture in a continuous or simple interrupted pattern. An intradermal suture pattern then closes the skin and subq.

Chinchilla Ovariohysterectomy

Indications and surgical approach for ovariohysterectomy are similar to those in other small mammals: neoplasia, dystocia, and disease of the reproductive tract. As with other herbivores, care must be taken to avoid damaging the cecum. The ovarian vessels of the chinchilla are short and do not allow for exteriorization. Care must be taken to avoid tearing these vessels during ligation.

Chinchilla Castration

Indicated to prevent reproduction and decrease undesirable sexual behavior. The surgical approach is identical to that used in guinea pigs. Additionally, it is important to check male chinchillas for prepucial fur rings, which can accumulate and form a restrictive band.

Hedgehog Ovariohysterectomy

Hedgehogs are prone to uterine hyperplasia and neoplasia. The uterus and ovaries are arranged like those of a cow, with the uterine horns coiled caudally, and the ovaries situated within the coil. Often, the OVH procedure can be quickly completed using 3 to 4 surgical clips.

Sugar Glider Ovariohysterectomy

Female reproductive issues are relatively uncommon. The reproductive anatomy the female sugar glider is unusual: a single urogenital sinus branches into a single median and two lateral vaginas. The left and right lateral vaginas each encircle a ureter and then rejoin the median vagina proximally at the cervices (as in the rabbit, each uterine horn has a separate cervix). Ovariohysterectomy therefore requires careful avoidance of the ureters.

        Surgical Technique

A midline abdominal approach is recommended, however it is complicated by the ventrally located pouch. Clip and prepare the ventral abdomen and the area around the marsupium. Make a 1-2cm paramedian incision around the pouch, allowing sufficient margin for skin closure after the laparotomy. Using blunt dissection, identify the linea alba and make an incision into the abdominal cavity. Identify the urinary bladder and carefully retract it to expose the reproductive tract. The ovaries are tiny, red, and granual in appearance. Ligate the ovarian branch of the ovarian artery. Next, ligate and remove the uteri where they come together to meet the lateral vaginal canals. Ligating distally to this point could result in ureteral occlusion. Close the linea alba in routine fashion. Return the pouch to its normal position, closing the skin with SC sutures and tissue adhesive

Sugar Glider Castration

Prohibits paired gliders from breeding. Also reduces odor and urine marking behavior, and prevents "balding" due to glandular development on the head and chest. In a mature sugar glider, the hair will regrow in about 3-4 weeks after castration. The scrotum is located cranial to the penis, on the ventral abdomen. It is suspended on a long stalk, making scrotal ablation the preferred method. However a scrotal approach to orchidectomy is also described. Since Sugar Gliders commonly exhibit persistent tendencies to chew/tear at incisions or sutures,a cauterizing procedure is strongly recommended by the ASGV. This technique involves placing a hemostat on the "stalk" close to the body and leave in place for several minutes. Then using electrocautery or a CO2 laser remove the scrotum and testicles distal to the hemostat. The hemostat is removed and the sugar glider is allowed to wake up in his pouch with a piece of apple (for distraction).

Suggested Reading

1. Bennet RA. Elective surgeries in small mammals. Proc of the North Am Vet Conf 2007: 1624-1627.

2. Capello V, Lennox AM. Gross and surgical anatomy of the reproductive tract of selected exotic pet mammals. Proc of the Assoc of Avian Vet 2006: 19-28.

3. The Veterinary Clinics of North America – Exotic Animal Practice. Soft Tissue Surgery, September 2000 3:3.

4. Quesenberry K, Carpenter J: Ferrets, Rabbits and rodents, Clinical Medicine and Surgery, 2nd ed. Saunders, 2003.

4. Bartlett L, Lightfoot: The exotic guidebook, Exotic Companion Animal Procedures, Zoological Education Network, Lake Worth.