Surgery of Exotic Animals. Группа авторов

used for irrigation of the gills to return to a container placed underneath the table for recirculating systems (see Figure 5.2). For laterally compressed fish, a V‐shaped foam tray is useful to keep the fish in dorsal recumbency. Irrigation of the gills is performed using a Y‐shaped perforated tubing or two tubes connected to submersed pumps as previously described (Figure 5.2) (Weber et al. 2009; Mylniczenko et al. 2014). If an oral cavity procedure is performed, the tubing may be placed with retrograde flow in each opercular cavity with water irrigating the gills from their caudal aspect (Figure 5.3) (Mylniczenko et al. 2014).

Figure 5.2 Anesthetic equipment used for a large 8 kg koi (Cyprinus carpio) anesthetized for a surgical procedure: a Doppler probe protected by a glove filled with conducting gel is placed in the left opercular chamber for heart rate monitoring and two tubes, each connected to a submersible pump are placed in each opercular cavity.

      Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.

Figure 5.3 Intervention in the oropharyngeal cavity of a Ranchu goldfish (Carassius auratus): a suture from a previous incisional biopsy is visible on the mass extending from the left commissure to left side of the face, ventral to the left eye. Irrigation of the gills is achieved with tubing placed caudally in each opercular cavity, which allows maintenance of anesthesia.

      Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.

      Surgical Modalities

Modalities such as cryosurgery and CO₂ laser have been used extensively in fish for mass ablation (Figure 5.4) (Francis‐Floyd et al. 1993; Harms et al. 2008; Boylan et al. 2015). These modalities improve hemostasis but do not allow for histologic evaluation and no study has demonstrated superior results using these modalities in fish. Protocols are extrapolated from those used in mammals. Hand‐held electrocautery can be used for hemostasis, but electrosurgery should not be used due to the omnipresence of conductive water (Figure 5.5).

Wounds

Wound healing has been studied extensively in zebrafish (Danio rerio) (Rapanan et al. 2015). Fish have exceptional regenerative capability (Ochandio et al. 2015). Fish skin has intrinsic healing properties, and products derived from fish skin are under investigation for xenografts (Baldursson et al. 2015). Healing time depends on environmental parameters such as water temperature, alkalinity, pH, salinity, and photoperiod (Andrews et al. 2015). Skin healing may take months in a cold‐water species. Keeping the patient at the higher end of its temperature range hastens healing time (Andrews et al. 2015; Ang et al. 2021).

Figure 5.4 Use of adjunctive cryotherapy for excision of an odontoma in an angelfish (Pterophyllum dumerilii) presented for recurring maxillary masses.

      Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.

Figure 5.5 Use of a hand‐held electrocautery during a lateral celiotomy in a silver arowana (Osteoglossum bicirrhosum).

      Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.

      For wound debridement, follow the same principles as those used in mammals. Debride necrotic tissues and remove detached scales from the wound and surrounding damaged tissue (Wildgoose 2000). Repeated debridement may disrupt the apical epidermal cap and is not recommended as this delays wound healing (Harms and Wildgoose 2001). Appose large clean fresh traumatic wounds with suture (Wildgoose 2000).

As in mammals, in cases of external ulcerations, the etiology should be investigated to prevent recurrence (Figure 5.6). Improper life support system design, such as an over‐sized pump, misplaced water inlets or outlets, or misaligned or improper filtration equipment can cause traumatic injuries to fish. Prolonged pond treatments, electrical currents, or chemicals in the water such as seen with an overdose of salt treatment for freshwater fish and/or copper intoxication may cause hyperexcitability leading to traumatic injuries. Predators such as piscivorous birds, river otters, and domestic or feral cats can kill small fish and injure larger animals. In cases of buoyancy problems, skin subjected to air exposure or rubbing against a tank substrate can cause ulcerations (Britt et al. 2002). Provide a nonabrasive pond substrate during healing such as with the addition of a soft plastic lining at the bottom and sides of the pond.

Figure 5.6 Large ulceration on the ventrum of a female koi (Cyprinus carpio) with coelomic distension due to egg retention. Treating the egg retention is important for skin healing in this case.

      Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.

      The use of becaplermin (Regranex^®, 0.01% gel, Ortho‐McNeil Pharmaceutical Inc., Raritan, NJ, USA), a recombinant platelet‐derived growth factor, improves skin healing after a single application (Boerner et al. 2003; Fleming et al. 2008). Apply becaplermin to the wound for 60 seconds every three weeks; this frequency is as efficient as more prolonged application (Fleming et al. 2008). Lavage the wound with sterile saline to loosen debris, gently debride necrotic tissues and exudates to create fresh vital tissue margins, rinse the wound again, and apply a thin layer of gel. After a contact time of 60–120 seconds, rinse the gel off or leave it on the wound. The use of topical manuka honey and aloe vera every four days with a three‐minute contact time has been associated with accelerated wound healing in koi (Ang et al. 2021), while the use of a phenytoin and misoprostol powder or silver sulfadiazine gel has been associated with delayed wound healing