REPRODUCTIVE SURGERY

5.1 Male sterilisation

5.1.1 Orchiectomy and scrotal ablation

In marsupials, orchiectomy is performed with the animal in dorsal recumbency. Because the scrotal septum is prominent, testicles are each removed through separate

Fig.

Fig. 10.7. Scrotal ablation in a red-tailed phascogale (Phascogale calura). (a) Placement of encircling ligature around the base of scrotal pedicle and (b) electrocautery to sever the pedicle. Photos: Larry Vogelnest

ventral scrotal incisions using an open castration tech­nique. The incisions are left open. Scrotal ablation is an alternative method and is being used more frequently. In larger animals an orchiectomy is performed as described above and the spermatic cords are ligated and severed as proximally as possible and pushed into the inguinal canals. The scrotal pedicle is then cut close to the abdominal wall and sutured (Vogelnest 2015). In small species, the intact scrotum can be removed by ligating and then severing the scrotal pedicle using a scalpel or electrosurgery (Malbrue et al. 2018; L Vogelnest pers. comm.) (Fig. 10.7).

Orchiectomy and scrotal ablation in the sugar glider using CO₂ laser to sever the scrotal pedicle in seconds with no postoperative complications has been described (Morges et al. 2009). An electrothermal bipolar tissue sealing device (LigaSure™, Covidien LLC, Mansfield, MA, USA) has been used to perform orchiectomy and scrotal ablation in sugar gliders and several species of macropod

(Cusack et al.

Hemicastration was performed on a male koala with a dilated spermatic granuloma and varicocele. The testicle was removed by routine excision and the koala remained fertile afterwards (Schultz et al. 2016).

In bats, a closed castration is performed through a prescrotal incision, because of the open inguinal ring (Olsson and Woods 2008). In otariids, the testes are scro­tal and castration is similar to that of a dog. Gage (2003) describes surgical removal of para-abdominal testes of phocids.

5.1.2 Vasectomy

In marsupials, the vas deferens is easily accessible through the scrotal pedicle. With the animal in dorsal recum­bency a skin incision is made midway along the cranial aspect of the pedicle. The tunica vaginalis is incised over the spermatic cord. A small portion of the spermatic cord is exteriorised and the vas deferens (the firmest white tubular structure in the spermatic cord) exposed by blunt dissection. A 0.5-1 cm segment is removed after ligating (or using vas deferens clips) proximally and distally. The incision is sutured and the procedure repeated on the opposite side (Vogelnest 2015).

Vasectomy in bats may be performed either through the ventral scrotum by locating the vas deferens where it exits the epididymis (Lafortune et al. 2004) or through a prescrotal incision (Olsson and Woods 2008).

5.2 Female sterilisation

5.2.1 Ovariectomy

The animal is positioned as for laparotomy (see section 4.3.1). An incision is made in the pouch midway between the tip of the epipubic bones and the pubis. Once in the abdomen, only one ovary is exteriorised at a time after locating the corresponding uterus. The fimbria and ampulla of the oviduct are teased off the ovary, the ovarian vessels are clamped and ligated and the ovary is removed before proceeding to the opposite side.

5.2.2 Ovariohysterectomy

The procedure in performed via a caudal midline lapa­rotomy incision (see section 4.3.1). Ovariohysterectomy is technically difficult in marsupials because of the pelvic location and unique anatomy of the urogenital tract. Once located, a hole is made in the broad ligament adjacent to the lateral side of the ovaries, avoiding the ureters. Ovaries are exteriorised, the vessels clamped and ligated. Once the ovaries are detached, the broad ligament is torn close to the lateral margins of the blood vessels to avoid damaging the ureters. The uteri are ligated at the proximal end of the cervices. They are ligated separately and then a single ligature can be placed around both uteri. Transfixation ligatures and stump closure with continuous suture pattern may also be required (Vogelnest 2015). Uterine stump/vaginal canal abscessation has been described as a complication following ovariohysterectomy for pyometra in a sugar glider (Koizumi et al. 2023).

In koalas with Chlamydia-associated ovarian bursal cysts, ovariohysterectomy can be complicated by exten­sive adhesions to the peritoneum, bladder and colon (T Portas pers. comm.).

In bats, tubal ligation and ovariohysterectomy are straightforward (Olsson and Woods 2008). In microbats, surgery may be facilitated by the use of magnification loops and microsurgical instruments. Haemoclips may be used on ovarian pedicles and the uterine body cranial to the cervix (Clarke and DeVoe 2011).

5.2.3 Oviducal transection

Sterilisation of koalas and macropods can be performed via laparoscopic transection and cautery of the oviduct. The abdomen is insufflated with CO₂ to 16-20 mmHg intra-abdominal pressure. Three small incisions are made adjacent to the epipubic bones, allowing insertion of grasping forceps, a laparoscope and cautery scissors into the caudal abdomen. Each oviduct is visualised and manipulated using forceps so that transection and cau­tery can be achieved without damage to blood vessels or other organs (Vogelnest 2015).

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