(Archibald et al. 2015).
Surgical harvest of oocytes from laboratory amphibians is a commonly performed procedure, especially to design transgenic frogs (Green 2010). To collect ova, place the frog in dorsal recumbency and perform a paramedian ventral incision with particular care to not puncture the lungs, the urinary bladder, or the enlarged ovaries. The ovaries with mature follicles extend ventrally in the coelom and are easily visualized (Figure 6.9). Grasp the ovaries with forceps and exteriorize them onto the plastic drape, as the skin is not sterile. Excise the desired number of oocytes using scissors. No ligature is necessary to collect a small portion of the ovary (Gentz 2007). Close the coelomic incision in two layers. Place simple interrupted sutures in the muscle layer and simple interrupted, vertical, or horizontal mattress monofilament sutures in the skin (Green 2010). The procedure can be repeated every three to six months in a single female.
Ovariectomy is performed in adult females. Make a ventral paramedian incision. Use an eyelid retractor to facilitate visualization. Exteriorize the ovaries onto the plastic drape with cotton tip applicators. Use electrocautery, diode laser (Chai 2016), place hemostatic clips, or ligate the ovarian pedicles with polydioxanone suture (Wright and Whitaker 2001a). Transect the pedicle and retrieve the ovary. After repeating the procedure contralaterally, lavage the coelom and suture the coelomic muscles and skin in two layers. If the muscular layer is very thin, place a collagen pad in the coelom to improve the security of the suture, especially in laying females (Meier 1982). Ovariectomy may predispose amphibians to becoming overweight (Wright and Whitaker 2001a).
Figure 6.9 Location of the ovaries (white arrow) in a reproductively active Gray tree frog (Hyla versicolor).
Source: Photo courtesy: Zoological Medicine Service, Université de Montréal.
Castration is performed in a similar manner to ovariectomy. Make a paramedian ventral incision and locate the intracoelomic testicles cranial to the kidneys. Testicular vessels are shorter than ovarian vessels. Gently elevate the testis to place hemostatic clips or ligating sutures. Use small overlapping hemostatic clips in large specimens rather than choosing large hemostatic clips which are more prone to slip if not closed appropriately resulting in hemorrhage. Cauterize the bilateral ductus deferens with electrocautery and transect the testicle distal to the clips. Close the coelom in two layers of monofilament suture. Testicular biopsy is used in laboratories for reproductive studies (Gentz 2007). Make a small paramedian ventral incision and locate the intracoelomic testicles located cranial to the kidneys. Obtain biopsies with a biopsy forceps: close the forceps, wait and apply gentle pressure before pulling on the forceps to retrieve the biopsy. Apply counter‐forces to the testicle with a cotton‐tip applicator to avoid damage to the vasculature supplying the testicle. Close the coelomic incision in two layers with monofilament suture. Alternatively, endoscopy‐assisted testicular biopsy can be performed.
Gastrointestinal Tract Surgery
For gastrotomy, after making a paramedian ventral incision into the coelomic cavity, place saline soaked gauze to isolate the area of interest and reduce the risk of contamination with gastrointestinal contents (Gentz 2007). Place stay sutures in the gastric wall (Figure 6.10) and perform the gastrostomy as in mammals. Close the stomach wall in one or two layers using monofilament absorbable suture material (Meier 1982) (Figure 6.11). If the diameter of the stomach is small, opt for a single inverting suture to decrease the risk of gastric stenosis. Postoperatively, offer the patient small meals or syringe feed a liquid diet for 4–6 weeks. Feeding live and chitinous prey items with abrasive body parts should be avoided during this period.
Cloacal prolapse is a common problem in amphibians (Wright and Whitaker 2001a; Fleming and Isaza 2000; Phillott and Young 2009). Cloacal prolapses should be differentiated from intestinal, urinary bladder, and reproductive organ prolapse, and perineal hernias.
After providing analgesia, soaking the prolapsed tissue in a hypertonic solution (e.g. 5% NaCl or 50% dextrose) for 5–10 minutes can help reduce its size (Wright and Whitaker 2001a; Hadfield and Whitaker 2005) and identify the prolapsed structures. If ureteral openings are exposed and appear necrotic, the prognosis is poor and euthanasia should be elected. If cloacal tissue is viable, cover the exposed cloaca with water‐soluble lubricant and reduce the prolapse with a blunt instrument (e.g. cotton‐tipped applicator or a red‐rubber tube) (Wright and Whitaker 2001a). With recurrent cloacal prolapses, a purse‐string suture may be placed with the cotton‐tipped applicator still in the vent to assure that feces will be able to pass once the suture is secured and the applicator removed.
If the prolapsed tissue includes necrotic intestine or reproductive tract, it should be amputated (Hadfield and Whitaker 2005) if reconstruction is possible. Resection and anastomosis of an intestinal loop or the salpinx may be performed externally before replacement of the prolapsed tissue. In females, perform an ovariohysterectomy after amputation of the prolapsed salpinx. If lesions are unilateral, a unilateral ovariectomy may be elected.
Cloacotomy has been described in a waxy monkey frog (Phyllomedusa sauvagii) presented with recurring urolithiasis after cystectomy (Archibald et al. 2015). Urolith formation recurred twice in the cloaca in this animal. The technique described to remove the calculus involved a paramedian coelomic incision followed by incision of the ventral cloacal wall. The cloaca was sutured with 5‐0 polydioxanone suture in a simple interrupted pattern and the patient recovered from this procedure.
Figure 6.10 Gastrotomy in an axolotl (Ambystoma mexicanum) anesthetized with a continuous effusion of 5 mg/l of alfaxalone delivered through plastic tubing visible on the left of each image. (a) Stay sutures with Prolene 5‐0 are placed on the coelomic cavity, (b) stay sutures are placed on the stomach on each side of the incision, and (c) rocks are exteriorized through the gastric wall incision.
Source: Photo courtesy: Dr. Marcie Logsdon, Exotics and Wildlife Department, Washington State University.
Figure 6.11 Gastrotomy in an axolotl (Ambystoma mexicanum): (a) suture of the stomach wall in a single layer with a continuous pattern of absorbable monofilament suture. (b) Recovery of the axolotl after suturing the skin with monofilament suture using a slightly everting continuous pattern.
Source: Photo courtesy: Dr. Marcie Logsdon, Exotics and Wildlife Department, Washington State University.
Minimally Invasive Surgery
Minimal
