Surgery of Exotic Animals. Группа авторов

enucleation due to the dermal plates greatly reducing the elasticity of the skin.

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

Coelomic Surgery

The coelomic cavity may be approached ventrally or laterally. For a ventral approach, make either an incision caudal to the pelvic fins just cranial to the vent (Figure 5.16) or an incision from the pectoral to the pelvic fins. If wider access to the coelom is needed, section the pelvic girdle on midline. The pelvic bones are joined on midline by a fibrous junction in some younger fish which becomes ossified in older specimens (Harms and Wildgoose 2001). During the approach, take care to avoid damaging the digestive tract, especially if a coelomic mass is displacing the intestine near the ventral body wall (Weisse et al. 2002; Weber 2011b). Perform a lateral approach or an L‐shaped incision in the coelom to access dorsal organs such as the kidneys or the swim bladder (Harms and Wildgoose 2001). Make the craniocaudal incision just ventral to the lateral line of the fish, extending from the caudal edge of the pectoral fin to the level of the anus. Make the dorsoventral incision at the level of the anus and extend as needed for exposure; do not incise too close to the sphincter of the anus.

      Coelomic adhesions are common in some species of fish including koi and are not necessarily an indication of coelomitis (Wildgoose 2000; Boone et al. 2008; Grosset et al. 2015). During the celiotomy, take care to limit traction on the coelomic wall as trauma to this delicate tissue can result in postoperative necrosis of the body wall. An assistant may gently retract the coelomic wall using a Farabeuf or Roux retractor or a self‐retaining retractor such as Heiss, Lone Star, or Gelpi retractors, or a Barraquer eyelid speculum may be used depending on the size of the fish (Harms and Wildgoose 2001).

Figure 5.16 Incision of the coelom between the pelvic fins and the digestive orifice in an anesthetized goldfish (Carassius auratus). A Lone Star retractor is placed on the coelomic cavity to facilitate visualization.

      Source: Photo courtesy: Zoological Medicine Service, Université de Montréal.

      Close the coelomic wall in two layers: muscle and skin (Harms and Wildgoose 2001). During closure, take care to close the pelvic girdle in accurate apposition if it has been sectioned. A subcuticular pattern rather than cutaneous suture is recommended in goldfish, as this induces less local reaction than simple interrupted sutures or interrupted horizontal mattress sutures (Nematollahi et al. 2010). Ideally, leave no additional air in the coelom during closure to avoid buoyancy problems. Also, consider the weight of suture materials and any prosthetics or surgical devices in very small patients (Britt et al. 2002).

      Do not remove sutures before four weeks (Shin et al. 2011). Sutures may be removed after four to eight weeks in temperate species (Sladky and Clarke 2016). Months may be necessary for adequate healing before suture removal in cold‐water species. Carefully examine the wound margins to assess skin continuity prior to suture removal.

Swim Bladder Surgery

The swim bladder is important in maintaining neutral buoyancy. Abnormal buoyancy is a common presentation of ornamental fish (Wildgoose 2007a) with a number of etiologies that can be diagnosed using radiography or other imaging techniques. Positive buoyancy may be due to overinflating of the swim bladder (Figure 5.17), torsion (rare), or gas in the coelomic cavity or other coelomic organs. Negative buoyancy may be due the accumulation of fluid in the swim bladder, infection, neoplasia, or compression by enlarged coelomic organs, cystic kidneys or ovaries, or other coelomic masses. Swim bladder anatomy varies greatly among fish species and surgeons should be familiar with the anatomy of their patient (Zebedin and Ladich 2013). Some fish are physostomous (swim bladder is connected to the digestive tract), some are physoclistous (swim bladder inflation is regulated by a gas gland), and some fish do not have a swim bladder (e.g. elasmobranchs, mackerels, tunas, benthic fishes, and remoras) (McCune and Carlson 2004). Koi and goldfish have a bi‐compartmentalized swim bladder with the most cranial compartment being more rigid and a pneumatic duct connecting it to the caudal compartment (Muir Evans 1925), while some catfish species have multi‐compartmentalized swim bladders (Zebedin and Ladich 2013). Imaging both the patient and a normal conspecific helps identify swim bladder lesions whenever specific anatomy has not been described (Schwartz et al. 2002; Pees et al. 2010). Care should be taken to avoid trauma to and deflation of the swim bladder during a celiotomy.

Figure 5.17 Right lateral radiograph of a positively buoyant goldfish (Carassius auratus) presented with multiple gas (white arrows) and fluid‐filled (black arrows) structures connected to the swim bladder.

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

      In the case of swim bladder neoplasia or distension, surgical reduction of the swim bladder is indicated. This procedure has been termed pneumocystoplasty or complete pneumocystectomy depending on the volume of swim bladder reduction (Britt et al. 2002; Lewbart et al. 1995). Approach the swim bladder using a ventral coelomic midline incision (Lewbart et al. 1995; Britt et al. 2002) or a L‐shaped incision through the lateral coelomic wall (Harms and Wildgoose 2001). For pneumocystoplasty, locate and preserve the pneumatic duct and/or the gas gland that is a “rete mirabile” and partially surrounds the walls of the swim bladder and furnishes a rich supply of blood often located ventrally on the most cranial aspect of the swim bladder (Harms and Wildgoose 2001). Carefully dissect the swim bladder to avoid perforation and collapse (Harms and Wildgoose 2001). The wall of the swim bladder is very thin and delicate and achieving impermeability following formation of a tear may be very challenging. This can result in free coelomic gas, abnormal buoyancy, and communication between the digestive tract and the coelom in physiostomous fish, which may cause coelomitis. Depending on the size of the fish, place an encircling ligature (Harms and Wildgoose 2001) or a vascular clip (Hemoclip, Teleflex, Morrisville, NC) prior to excising the affected part of the swim bladder (Britt et al. 2002). Alternatively, a two‐layer inverting suture may be placed to close the swim bladder after excision of a section of this organ (Sladky and Clarke 2016). Negative buoyancy is a common complication immediately following pneumocystoplasty as the fish needs to adjust gas content of the swim bladder to accommodate the weight of a hemostatic clip or for decreased size of the swim bladder itself. This complication may persist for the remaining life of the fish if the resulting volume of the swim bladder is too small (Sladky and Clarke 2016). On the Internet, several hobbyists and websites have suggested ways to create custom‐made flotation harnesses for goldfish using chamois material, plastic airline tubing, and cork to allow locomotion in negatively buoyant fish.

Reproductive Surgery

      Determining the sex of fish through surgical incision into the coelomic cavity is performed routinely in some fish industries. Commercial sturgeon is sexed around three year of age to separate males for meat production and females for caviar production. Caviar collection itself may also be accomplished antemortem through a coelomic incision followed by closure of the body wall; this technique is employed in some commercial facilities to allow production by the same female during subsequent