General Surgical Principles and Neutering

Anaesthesia and postoperative care are covered in Chapter 4. Endoscopy in rabbits is summarized in Table 13.1.

Table 13.1

As a general rule, the largest endoscope possible should be used. Large endoscopes give a better view, with good illumination and are stronger and less liable to damage.
Rigid endoscopes are most suitable for most endoscopic procedures in rabbits. They require an irrigation sheath that is used for flushing, sucking and insufflation. A larger sheath can be used to provide an instrument channel.
General anaesthesia is required.

13.1 Skin preparation

Rabbit skin is thin and prone to injury. It contains many hair follicles with multiple shafts of fine dense hair. Removing the hair without damaging the skin or clogging the clipper blades can be difficult. A good-quality, robust set of clippers is a sound investment. Rabbit hair is so fine that it quickly becomes trapped between fine clipper blades. Running the clipper blade slowly through the fur can prevent this. Depilatory creams can be used but tend to be messy and difficult to clean off satisfactorily. The application of excessive quantities of spirit to the operation site can cause heat loss, especially in small, thin rabbits. Excessive scrubbing or iatrogenic skin damage from the clippers may cause postoperative irritation, pain and possibly self-mutilation, especially around the perineum. Chlorhexidine in spirit (Vetasept, Animalcare) is suitable for preoperative skin sterilization as it can be used as a single application and does not require skin scrubbing.

13.2 Surgical considerations

Good illumination is essential for rabbit surgery. The tissue is thin, delicate and friable in comparison with the dog or cat. Some surgeons prefer to operate using optical loupes or an operating microscope. Transparent, plastic drapes are an asset as they allow the anaesthetist to observe the respiratory movements during surgery. A set of fine surgical instruments is required. A kit has been put together especially for surgery on rabbits (Animalcare, York). It contains a selection of 5” (12.7 cm) straight and curved Criles and Halstead forceps, Martin splinter forceps, Debakey (2 mm) and Adson (1/2cm 5”) dissecting forceps, an Olsen Hegar scissor needle holder and 5” (12.7 cm) straight sharp/blunt and 4.5” (11.5 cm) Strabismus scissors. A no. 9 scalpel blade and a pair of 6” (15 cm) straight Metzenbaum scissors are also included.

The blood volume of rabbits is 55–65 mL/kg (Gillett, 1994). Up to 10% of this amount can be lost without untoward effect: above 20–25% results in hypovolaemic shock.

Rabbits are prone to the development of adhesions after surgery. The omentum in rabbits is small and it is often not possible to omentalize viscera satisfactorily. Foreign material such as talc from gloves or lint from gauze swabs can induce adhesion formation. Gentle surgical technique with minimal tissue handling is important. Fat necrosis occurs readily, especially in the broad ligament. The fat decomposes into fatty acids and glycerol that combine with ions such as sodium, potassium and calcium. It is associated with trauma.

Rabbits are used extensively as experimental models of post-surgical adhesions in humans, especially after urogenital surgery. In laboratory rabbits, it has been discovered that calcium channel blockers are effective in preventing adhesions (Steinleitner et al., 1990). Verapamil (200 μg/kg), given subcutaneously every 8 h for a total of nine doses, can be used in situations where adhesions are likely to develop. Examples include surgery on the large intestine, ruptured pyometra or abdominal abscess removal.

13.3 Suture techniques and materials

Experimental studies have indicated that the size of the suture material is more important than tissue reactivity in adhesion formation (Holtz, 1982). Therefore, the choice of fine suture material in addition to good suture technique is important for minimizing adhesion formation in rabbits. Small-gauge (3/0, 4/0 or 5/0) modern suture materials swaged on needles are satisfactory. Polydioxanone (PDS 11) or poliglecaprone (Monocryl, Ethicon) can be used for most situations, although 3/0 or 4/0 catgut is suitable to tie off blood vessels or ligaments.

13.4 Abdominal incisions

A midline approach through the linea alba is suitable for most abdominal procedures in rabbits. A good choice for repairing the incision is 4/0 polydioxanone (PDS 11) as it has high tensile strength and is degraded slowly. An alternative is 4/0 poliglecaprone (Monocryl, Ethicon). The abdominal fascia is repaired in a single layer. Studies in rabbits have shown that a double-layer abdominal closure has no advantage over a single-layer technique (Nilsson, 1981). The knots at the ends of the suture must be made with particular care if a continuous suture is used. The first throw draws the edges of the fascia together without crushing. An additional four throws are required at the start of the suture and six at the end (Bouvy and Dupré, 1997). Alternatively, a row of simple interrupted sutures can be used. Skin closure with a continuous subcuticular suture with a buried Aberdeen knot is recommended (see Figures 13.1 and 13.2) (Flecknell, 1998). Additional skin sutures or tissue adhesive can be used, if necessary. Owners appreciate skin sutures and worry that the patient has removed them if they cannot be seen. It is important that the abdominal incision is repaired securely and without tension on the sutures. Tight sutures and ischaemia of the peritoneum increase the risk of abdominal adhesions (Niles and Williams, 1999). If the suture line is comfortable, most rabbits will leave the incision alone, although some will remove the skin sutures. If the subcuticular suture is secure, this is not important.