Page 562 - WSAVA2018
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 25-28 September, 2018 | Singapore
into the retroperitoneal space as the testicular vessels are branches off the renal vessels. Haemorrhage from these vessels, therefore, occurs in the retroperitoneal space and does not cause haemoabdomen. Inadequate control of subcutaneous vessels and vessels within the tunics are the likely causes of scrotal hematomas, not haemorrhage from the testicular vessels.2
A modification of this technique in rabbits involves an open castration being careful to remove only the testicle and leaving the epididymal fat pad intact. The fat pad will then prevent herniation of intestine through the inguinal ring.2
With any of these techniques the scrotal incision may
be left open to heal by second intention or it may be sutured closed using either an intradermal pattern, tissue adhesive, or skin staples.
Rabbits: A 2-3 cm incision is made starting midway between the umbilicus and pubis extending caudally. The cecum and bladder may be directly under the
linea alba and it is recommended that the body wall be elevated from the abdominal structures prior to making the initial incision in the linea alba. Once the peritoneal cavity is opened the viscera will drop away as air enters the peritoneal cavity. The uterus is usually visible dorsal to (under) the cranial pole of the bladder. The uterine horn is usually redder in colour than surrounding
viscera, making it easily identifiable. One uterine horn may be lifted through the incision using atraumatic forceps. (It is best to avoid using a spay hook as such
an instrument may perforate the cecum leading to disastrous consequences.) Once the uterine horn has been elevated through the incision it is traced to the ovary which is loosely attached to the dorsal body wall by a long, fat-filled mesovarium. The oviduct is usually visualized as a fine tubular structure which literally encircles the ovary. A clamp may be placed between the ovary and the uterine horn to allow traction to be applied to the ovary. The ovarian ligament does not usually need to be broken down. There are many vessels that supply the ovary within the fat of the mesovarium. An opening
is created by blunt dissection through the fat of the mesovarium and a ligature is passed around the portion of the mesovarium containing the vessels supplying the ovary. As the suture is tightened it will cut through the
fat, but will ligate the blood vessels. This procedure is repeated on the contralateral side and the fat-filled broad ligament of the uterus may be broken down by gentle blunt dissection. Any large vessels or any haemorrhage from vessels within the broken ligament may be controlled by ligation or haemostatic clips. Following dissection of both uterine horns the uterus may be ligated on either the cranial or the caudal side of the cervix. The uterine vessels lay on each side of the uterus several millimetres lateral to the uterus. It is best to
ligate these vessels individually and place a transfixation ligature around the uterus prior to transection. Closure is routine with body wall, subcutaneous tissue, and skin being closed as separate layers.2
Guinea pigs: Two approaches can be used: a ventral midline approach as described above, or a bilateral flank approach. The latter approach is particularly useful in young sows as it minimises the risk of handling the intestinal tract. The 1cm skin incision starts where the last rib passes under the lumbar muscles, and is directed
at a 45o angle caudoventrally (the author directs it towards the stifle). The subcutaneous fat is separated (or removed) and the muscle wall is incised along the same line as the skin incision. Peritoneal fat comes into the incision, and when exteriorised gently with atraumatic forceps, it contains the ovary and/or fallopian tube.
The ovarian blood vessels, between the ovary and the kidney, are ligated and transected and the fallopian tube followed caudally to the uterine horn. As much horn as possible is exteriorised, ligated and transected. The muscle, fat and skin are closed in separate layers and the procedure repeated on the other flank. If needed, the remnants of the uterine horn and the uterine body can be removed via a small ventral midline incision.
Post-operative care
Post-operative complications include:
· Pain (see the earlier discussion on analgesia)
· Ileus occurs when the animal is inappetant, dehydrated, in pain, or all of these. Animals should be well hydrated before and after the surgery, fasting should be minimised, analgesia provided and, if the patient in not eating, it should be assist fed with a suitable diet (e.g. Critical Care®, Oxbow), Animals should not be discharged after surgery until they have been seen to eat and defecate.
· Infection is most common in guinea pig cas- trations, with abscess formation under the skin incision occurring several days after the proce- dure. Post-operative antibiotic therapy should be considered, and the owner advised to watch for swelling at the surgery site
· Scrotal herniation can occur in both rabbit and guinea pig castrations, and the owners should be advised to monitor the site for swelling.

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