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 (Coutant et al. 2019; Ang et al. 2021).
Skin Surgery
The indication for surgery should be confirmed before performing a procedure. Surgical excision of masses associated with lymphocystivirus or cyprinid herpesvirus 1 (CyHV1) infections is not recommended, as they will spontaneously regress (Weber 2013). Surgical preparation should not disrupt the natural mucus layer of the integument. Mucus is critical for innate immunity and protection (Benhamed et al. 2014; Guardiola et al. 2014). Scale removal is recommended to facilitate skin closure and healing (Wildgoose 2000). Gently extract the scales with a pair of forceps along the incision line. Since fish scales are dermal in origin (Lee et al. 2013), this can damage the epidermis and should be accomplished with care to limit the resulting trauma to the skin and to leave the scale bed intact so that scales will regrow normally (Weber et al. 2009). Then gently flush with sterile saline or sterile water rather than typical surgical preparations (Lloyd and Lloyd 2011), as many surgical antiseptics have been reported to predispose fish to dermatitis and incisional dehiscence (Mylniczenko et al. 2007). Irrigate exposed skin and eyes with chlorine‐free water throughout surgery to avoid desiccation and secondary necrosis.
For skin biopsies, use a biopsy punch or scalpel blade. Achieve hemostasis using digital pressure or hand‐held electrocautery. Biopsy sites can be left open to heal by second intention. Compared to mammals, fish skin has very low elasticity due to the dermal scales (Wildgoose 2000). External mass incisional or excisional biopsy in fish is accomplished in a manner similar to that in mammals. Surgical margins are rarely obtained for neoplasia that involves the coelomic cavity (Figure 5.7) and body wall reconstruction should be planned carefully prior to mass resection due to the low elasticity of the tissues (Boerner et al. 2000; Wildgoose 2000). Intralesional chemotherapy based on a histologic diagnosis has been reported (Figure 5.8) (Vergneau‐Grosset et al. 2016; Stevens et al. 2017).
Figure 5.7 Excision of a neoplastic mass of the vent of a koi (Cyprinus carpio): the integrity of natural orifices and anatomy should be preserved as much as possible during mass excision.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Operculoplasty is performed for esthetic purposes in fish with a laterally curled operculum, a common congenital problem in arowanas (Osteoglossum and Scelopages spp.) (Figure 5.9a). The etiology has not been determined and a genetic predisposition cannot be ruled out. Section the operculum with scissors at the level where it is still parallel to the long axis of the body (Figure 5.9b) and it will grow back straight. Some hobbyists also recommend filing the exposed opercular to the appropriate angle, but care should be taken not to damage the surrounding epithelium.
Oral surgery and incisive plate adjustments may be needed to improve food prehension due to insufficient wearing of the dental plates (Figure 5.10) or due to the presence of an oral mass. Incise the fibrous tissue with a scalpel blade in a medial to lateral direction and allow healing by second intention. Pufferfish have continuously growing incisor plates (Lécu and Lecour 2004). When fed exclusively soft food items such as pelleted diets, flakes, or soft prey instead of a natural diet that includes mollusks or crustaceans, they can develop overgrowth of their incisor plates (Figure 5.11a). Trim these plates with a dental burr or rotary tool (Dremel, Racine, WI) (Lécu and Lecour 2004) (Figure 5.11b). Take care to not overheat the incisor plates by prolonged contact with the burr. It may be necessary
