Stephen J. Hernandez-Divers, BVetMed, CBiol, MIBiol, DZooMed, MRCVS, DACZM, RCVS
Specialist in Zoo & Wildlife Medicine, Exotic Animal, Wildlife & Zoological Medicine, Department of Small Animal Medicine & Surgery, College of Veterinary Medicine, University of Georgia
Athens, GA, USA
In general, performing surgery on a reptile patient should be approached with the same principles as those used for domestic animals. However, there are some specific anatomical considerations, as well as unique aspects of patient preparation, positioning and equipment with which the reptile clinician should be familiar. The complexity and vastness of reptile surgery in over 6500 species necessitates the incorporation of only the most important factors and the most common procedures. Much detailed information has been omitted and cross-reference to other texts on reptile anatomy, physiology, husbandry, anesthesia, and surgery is required (Frye, 1992; Hernandez-Divers, 2004; Mader, 1996).
Anatomic Considerations. Although there are some major anatomical characteristics that distinguish reptiles from mammals, the Class Reptilia is a large group comprising of 6500 different species. Therefore, it is difficult to generalize on the anatomy of reptiles. The clinician wishing to perform surgery on a reptile patient should first familiarize himself/herself with the external and internal anatomy of that specific species. Even within the same order, there can be variations of the internal anatomy that are very significant. A good example is the fact that some members of the Order Squamata Suborder Saurian posses urinary bladders (Iguana sp), while others do not (Varanus sp.).
Surgical Instrumentation. It can be challenging to maintain a pre-packaged exotic surgery kit that is applicable for a wide variety of species and procedures. For truly giant reptiles, including giant tortoises and crocodilians, the use of stronger large animal instruments is recommended. Likewise for reptiles weighing 5-50kg, most small animal instruments are appropriate. However, most exotic patients are less than 5 kg in size, and the majority are less than 1 kg. For these smaller reptiles, microsurgical instruments are often required. Micro-instruments, which are not miniaturized versions of standard instruments, but rather balanced instruments with fine, small tips, are the optimum instrumentation for this size of patient. Since micro-instruments can be costly, other viable options are ophthalmologic instruments. Standard iris scissors, tenotomy scissors, Castroviejo needle holders, and colibri forceps can be very useful. One of the most important considerations in surgery is exposure. Plastic, self-retaining retractors (e.g., Lone Star retractor) can be adjusted to fit different sizes of incisions and do not compromise the ventilation of these patients. Smaller versions of standard abdominal retractors such as paediatric Balfour retractors, Haight baby rib spreaders etc can also be utilized, but are significantly heavier. Eyelid retractors can be useful for retracting coelomic incisions in small lizards and snakes. A variety of surgical drills and saws should also be available. Autoclavable or gas sterilizable models are preferred. For general orthopaedic work, the Stryker drill offers excellent control and versatility, even for the smallest of patients. The oscillating saggital saw attachment to the air-powered 3M mini-driver provides fine control and reduced tissue trauma compared to rotating saws. Small versions of suction tips, ronguers, elevators, and bone holding clamps are also useful. Epoxy resins (Enviroset 5 minute epoxy, Environmental Technologies Inc) or low-temperature veterinary acrylics (e.g., Technovite 8100 MG kit) are used for many chelonian plastron closures and shell repairs. A two polymer orthopaedic putty (Veterinary Instrumentation Ltd) is also a very useful aid to external fixation. A selection of intramedullary pins, miniature fixator pins, aluminium/carbon fibre clamps and titanium/carbon fibre support rods complete the fracture repair equipment (IMEX Veterinary Inc). Modern rapid absorbable suture materials (e.g., polyglactin 910, polyglycolic acid) are recommended for internal soft tissue applications. For permanent internal durability, polydioxanone or nylon are required. Monofilament nylon and polydioxanone are favoured for skin suturing, although wire may be necessary for crocodilians and giant tortoises.
Magnification and Illumination. Proper lighting is an obvious requirement for surgery. However, it becomes even more important in small patients. Therefore surgical lights that are powerful enough and can be focused to a small region will be useful. Most reptile patients that present for surgical care are significantly smaller than mammalian patients, for example, the bladder of an adult green iguana is only 0.2 mm thick. Therefore, some degree of magnification is generally recommended. There are a variety of magnification systems available. Operating microscopes (e.g., M501, Leica Microsystems (UK) Ltd) are versatile, but can be prohibitively expensive for the private practitioner to purchase new, although used models are frequently available. Headband or frame-mounted operating loupes (2.5x magnification) with a dedicated halogen or xenon light source, are affordable, versatile, comfortable, and simple to use (Surgitel, General Scientific Corporation).
Hemostasis. A healthy reptile can generally tolerate between 0.4-0.8 ml/100g bodyweight of blood loss. Patients in need of surgery are often compromised and diagnostic blood samples may have been collected prior to surgery. Therefore, the amount of blood that a reptile can afford to lose during surgery may be considerably less. Careful consideration must be given to reducing haemorrhage to a minimum.To allow the surgeon to apply localized pressure to a small vessel and keep track of blood loss, cotton-tipped spears or applicators are less traumatic and more manageable in small confined spaces than standard gauze squares. Vascular clips (Weck Closure Systems) are a convenient and effective way to clamp vessels. The Weck system utilizes autoclavable applicators and clips of various sizes-the medium size appears most versatile. The application of vascular clips is faster than standard suture ligatures, and therefore their use significantly decreases operating time. Radiosurgery utilizes high frequency radiowaves to cause focal thermal tissue damage. Unlike electrocautery, radiosurgery maintains a cool electrode, and offers superior accuracy and reduced collateral damage that rivals laser incisions. The 4.0 MHz dual radiofrequency Surgitron (Ellman International Inc) offers monopolar/bipolar applications with foot-pedal/finger switch control for cut, coagulate, haemostasis, fulgarate, and bipolar modes. Monopolar cutting needles are typically used for dissection, wire loops for tissue biopsies, and bipolar forceps for sealing blood vessels. Laser (Light Amplification by the Stimulated Emission of Radiation). The CO2 laser (10,600 nm) is probably the most commonly used veterinary laser and offers ultrafine bloodless dissection (Accuvet, Lumenis (UK) Ltd). In contrast, the diode lasers (980 nm) are less expensive, can seal blood vessels up to 2 mm in diameter, but tend to produce more collateral damage. Both types of laser require enhanced human safety precautions including a sealed, windowless surgery room, and the use of protective glasses, specific for the wavelength of laser being used.
Patient Positioning & Surgeon Ergonomics. Precise patient positioning will depend upon the species and the nature of the surgery. Rather than assuming contorting positions, the surgeon must dedicate some time to planning factors such as patient positioning and table height. The ideal posture for the surgeon involves sitting with a straight back, and a slightly flexed neck. In addition, when performing microsurgery, the arms and wrists should rest on the surgical table. In most cases, utilizing sand bags or similar objects to support the wrist, allows the surgeon the most optimal motor control when incising or suturing delicate tissues. Poor positioning will quickly lead to surgeon fatigue, reduced surgical ability, and increased patient morbidity.
Pre-Surgical Preparation. Aseptic surgery should ideally be carried out in an appropriately clean and sterile room by surgeons wearing surgical masks, hats, sterile gloves and gowns. The surgical site should be aseptically cleaned using chlorhexidine or povidone-iodine concentrate-a toothbrush is particularly useful for cleaning scaled skin. Dousing with alcohol is not recommended because of increased evaporative heat loss; however, a final alcohol wipe will ensure a dry grease-free area to which adhesive drapes will readily stick. Traditional cloth drapes may be heavy and hinder anesthetic monitoring. Transparent, adhesive drapes (Surgical drape, Veterinary Specialty Products) have several advantages, including 1) better visualization and monitoring of the patient, 2) maintenance of a waterproof barrier, 3) secured without towel clamps, and 4) lightweight.
Surgical Procedures. Commonly performed surgical procedures include wound debridement and repair, abscess/neoplasm removal, tail/digit amputation, esophagostomy tube placement, prolapse replacement/repair, fracture/shell repair, endoscopy and coeliotomy for organ biopsy, reproductive sterilization, dystocia correction, or enterotomy/enterectomy. Space limitations do not permit detailed description in the text, but detailed examples will be provided in the lecture.
1. Frye, FL (1992) Biomedical and surgical aspects of captive reptile husbandry. Krieger, Malabar.
2. Hernandez-Divers SJ (2004). Surgery: principles and techniques. In: Manual of Reptiles, Second edition. Edited by Raiti P and Girling S. British Small Animal Veterinary Association, Cheltenham, England. Pp 147-167.
3. Mader, DR (2005) Reptile Medicine and Surgery. Second edition. WB Saunders, Philadelphia.