pufferfish frequently to avoid inflation of the esophagus with air rather than water; water distention of the esophagus in these species is a normal physiologic defense, and fluid can be more easily expelled post procedure than entrapped gas (Wildgoose 2000).
Figure 5.8 Intralesional bleomycin injection into a myxoma on the head of an oranda goldfish (Carassius auratus). This treatment led to a decrease of the size of the mass for the following three months and was subsequently repeated as needed.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Orthopedic Surgery
Successful surgical stabilization of mandibular symphyseal fractures has been reported in three arowanas (Lloyd and Sham 2014). Two 19‐gauge needles were placed on each side of the mandible and a 4‐metric stainless steel orthopedic wire was passed through the needle holes and tightened up to stabilize the fracture. Successful repair of a luxation of the dentaro‐ectopterygoid joint in a fish has been performed (Dr. Freeland Dunker, Steinhart Aquarium, personal communication). The fish presented with an inability to close its dentary bone. Under general anesthesia, the mandible was closed with external manipulation, and a cerclage wire was placed on the premaxillary and dentary bones to keep the oral cavity closed. After a few weeks, the cerclage was removed and the fish was able to open and close its mouth and to eat spontaneously. Scoliosis correction in koi has been attempted by stabilizing the vertebrate with screws, k‐wire, and polymethylmethacrylate (Govett et al. 2004).
Figure 5.9 Opercular plasty in an anesthetized Asian arowana (Scleropages formosus): (a) the caudal part of the right operculum appears curved laterally and shortened; (b) the operculum is sectioned with scissors after butorphanol and local anesthesia have been administered.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Figure 5.10 Fibrous tissue obstructing the oral cavity of a koi (Cyprinus carpio).
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Ophthalmic Surgery
Fish eyes have marked anatomic differences compared to those of mammals (Kern 2007). Very few fish have eyelids, except some elasmobranchs. They have larger lenses comparatively to mammals of the same size, and the lens protrudes into the anterior chamber, which has implications for cataract surgery (Kern 2007). The posterior segment of the eye contains a falciform process and a choroid rete communicating with the pseudobranch in most species (Copeland and Brown 1976). An important consideration when performing an enucleation is the presence of scleral ossicles in the anterior part of the globe, as in teleosts, and scleral cartilage or scleral calcifications in the posterior part in elasmobranchs (Pilgri and Franz‐Odendaal 2009).
The pupillary light reflex is usually absent, except in elasmobranchs (Duke‐Elder 1958). They have a slow retinomotor reflex that takes up to two hours. During the day, retinal‐pigmented epithelium granules migrate apically in the retinal epithelial cells, cones contract and rods elongate (Burnside et al. 1983). This retinomotor reflex protects photoreceptors from bright light, but rapid exposure of anesthetized patients to a scialytic lamp may impair vision and some authors have recommended covering fish eyes with an opaque material during surgery (Wildgoose 2000).
Figure 5.11 Green spotted pufferfish (Tetraodon nigroviridis) before (a) and after incisor plate occlusal adjustment (b).
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Figure 5.12 Fluorescein staining of a large corneal ulceration in a lookdown (Selene vomer) associated with repeated trauma on the walls of the exhibit.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Corneal ulcers can be highlighted by the use of fluoresceine dye (Figure 5.12). Repair corneal perforations with small diameter suture material and use periorbital tissue to cover peripheral corneal perforations, similar to a conjunctival flap.
Idiopathic gaseous exophthalmia (i.e. not due to gas oversaturation of water) has been treated with pseudobranchectomy. The pseudobranch is located dorsally in the opercular cavity in most teleosts (Harms and Wildgoose 2001). Visually locate the pseudobranch and apply electrocautery on various points to cauterize it.
Some fancy goldfish, such as oranda and lionheads, are bred to have a fleshy outgrowth on the dorsal aspect of the skull and bilaterally in the buccal area, which is called a crown or “wen.” This wen is a hyperplastic epidermal and mucous cell covering of adipose cell deposition in the hypodermis (Angelidis et al. 2006). The wen grows continuously, sometimes covering the eyes and impairing vision. Use a scalpel or electrocautery to excise the periocular tissue (Sladky and Clarke 2016).
Cataract Surgery
Cataract surgeries have been performed in fish, either with complete lens removal (Whitaker 1999; Adamovicz et al. 2015) or with phacoemulsification of the lens content in specific cases (Adamovicz et al. 2015; Bakal et al. 2005). After applying topical proparacaine and atropine, fill the anterior chamber with viscoelastic material and incise the dorsal cornea with a 2.75 mm keratome (Adamovicz et al. 2015) or a 11# scalpel blade. The authors recommend a dorsal incision of the cornea as it allows easier access to the retractor lensis muscle located ventral and caudal to the lens (Gustavsen et al. 2018). To prevent collapse of the anterior chamber, incise the cornea perpendicular to its surface initially, then with a more acute angle. Extract the lens, which physiologically protrudes into the anterior chamber, “en masse” with a Graefe cataract spoon through the corneal incision (Whitaker 1999). Close the cornea with simple interrupted 5‐0 to 9‐0 sutures. Apply a cyanoacrylate ophthalmic tissue adhesive (optional) to ensure impermeability of the cornea during healing (Whitaker 1999).
