Page 560 - WSAVA2018
P. 560

 25-28 September, 2018 | Singapore
B. Doneley1
1Avian and Exotic Pet Medicine, The University of Queensland, Gatton, Queensland, Australia
Desexing of rabbits and guinea pigs is a commonly requested procedure in exotic animal practice. Both
the anaesthesia and the surgical procedures in these species are complicated by differences in anatomy and response to anaesthesia and surgery. This paper reviews the surgical anatomy of these species, anaesthetic considerations, surgical procedures and common complications.
Reasons and age for desexing
Desexing in rabbits in guinea pigs is performed for three main reasons:
· To control reproduction
· Rabbits reach sexual maturity at 4-8 months of age (depending on their size: small breeds mature at 4-5 months, medium breeds at 5-6 months and large breeds at 5-8 months. Each doe can have up to 10 litters a year, each litter with 4-10 kits.
· Guinea pigs reach sexual maturity at 2–3 months of age. Each sow can have numerous litters each year, each with anywhere between 1-13 offspring
· To prevent disease
· Entire rabbit does have a high incidence of uterine adenocarcinoma, the most common neoplasm in rabbits. The study by Greene (1959) showed that 4% of does had uterine cancer at age of 2-3 years, rising to 60-80% at 5-6 years. Whether the rabbit has had a litter does not appear to affect this incidence; the incidence increases with age.
· Entire guinea pig sows have a high incidence of cystic ovaries. Although
the majority of these cysts are non-func- tional rete ovarii cysts, they can have a spacy-occupying mass effect. Functional cysts frequently cause hormonal alope- cia and uterine changes
· Male rabbits and guinea pigs do not ap- pear to have any significant sex-related medical problems
· To prevent or manage behavioural reasons
· Entire rabbits of both sexes often be-
play aggression towards other rabbits, other animals and even their owners
· Entire male rabbits housed alone may have marked sexual behaviours, mating with other animals and even inanimate objects
· Entire guinea pigs of either sex may develop similar behavioural issues, although not as marked as rabbits
· Desexed rabbits and guinea pigs of both sexes are usually more docile, less destructive, and are better ‘pet quality’ animals
Rabbits are generally desexed at 3-6 months of age.
It can be difficult to determine gender if the testicles have not descended, which occurs around 12 weeks of age – it is therefore worth waiting until the animal can be accurately sexed. Guinea pigs are easier to sex at an earlier age, and are often desexed at around 6-8 weeks of age.
Surgical Anatomy
The ovaries of rabbits are not located in a true ovarian bursa but are usually surrounded by fat within the mesovarium and the mesosalpinx. The uterus of young rabbits is found just dorsal to the bladder, coiled in the caudal abdomen. In older rabbits, the cervix is dorsal to the bladder, but the horns extend laterally. The uterus and ovaries are generally easy to exteriorize; however, they are more fragile than those of dogs and cats. The uterus is bicornuate and each horn has its own cervix. There is no distinct uterine body. The mesometrium of rabbits is a site of fat storage. In obese rabbits this can make surgery more challenging as it is often difficult to definitively identify the ovarian and uterine vessels for ligation. The vaginal body is a long, large, and flaccid unpaired organ, and the urethra opens into the ventral aspect of the vaginal body. This marks the division between the vestibulum, which is caudal to the urethral opening, and the larger true vaginal body, which is cranial to the urethral opening.
The testicles of rabbits are elongated, not round, and they move freely between the abdomen and the scrotum through the function of a well-developed cremaster muscle. The epididymis is located at the caudal pole
of the testicle, but it is not as developed as in guinea pigs. The inguinal canal is open in rabbits; however, the intestine does not usually herniate because of the large epididymal fat pad which fills the inguinal canal when
the testes are within the scrotum and the inguinal fat pads within the abdomen2. The proper ligament of the testis which attaches the tunica vaginalis to the scrotum is quite strong. The position of the testicles at any given time depends on many factors including body position, body temperature, breeding activity, gastrointestinal tract
  come territorial as they mature and dis-

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