NAVC Conference 2008 ______

SNAKE CLINICAL PROCEDURES AND from tail length/confirmation, or probing the inverted DIAGNOSTICS hemipenes.

Stephen J. Hernandez-Divers, BVetMed, DZooMed, DIAGNOSTIC IMAGING MRCVS, Diplomate ACZM Snakes can be difficult to position and restrain for College of Veterinary Medicine, radiographic examinations unless anesthetized. If the University of Georgia, Athens, GA purpose of the examination is simply to rule out radiodense foreign bodies, the snake may be allowed to coil in its natural position while the radiograph is taken. If There are very few pathognomonic signs in reptile detailed examination of the skeletal, respiratory, and medicine, and it is generally very difficult to make a digestive system is desired, the snake must be diagnosis in the examination room. Definitive diagnosis extended. A plastic restraint tube can be utilized for this is important to maximize therapeutic success, while purpose; however, this may produce some radiographic reducing the negative impacts of providing veterinary artifact. In larger snakes, several films will be needed to care. In general, diagnosis relies upon the demonstration radiograph the entire length of the body. It is important to of a host pathological response (eg, cytology, properly label each exposure in order to keep track of all histopathology, and serology) and the causative agent the different views. Lateral views are best taken using (eg, microbiology, toxicology). Diagnosis is often horizontal beams to avoid displacement artifact of the straightforward if appropriate samples can be collected, viscera. However, standard laterals with the snake taped processed and interpreted. This article focuses on the in lateral recumbency can be useful especially where most common techniques and procedures and is far horizontal beams are not possible or safe to undertake. from complete. Further details can be found in published The interpretation of dorsoventral views is hindered by texts. the spine and ribs, but can still be useful when dealing with obvious lesions including eggs and mineralized CHEMICAL RESTRAINT masses. While some procedures can be performed in the Traumatic fractures, spondylitis/spondylosis, conscious snake, sedation or anesthesia can facilitate osteomyelitis, and congenital abnormalities are common procedures, and reduce trauma to the animal. A review indications for examining the skeletal system of snakes. of snake anesthesia appears elsewhere in these Fractured ribs with periosteal bone formation are a proceedings, and detailed reviews are available common finding in snakes. Another common finding is elsewhere. exuberant vertebral periosteal bone formation. On radiographs, this appears as several "fused" vertebrae. HANDLING & EXAMINATION Common indications for radiographically evaluating the A detailed review of husbandry and past medical digestive system include hypertrophic gastritis, foreign history is required prior to physical exam. The head of an body ingestion/impaction, constipation, hepatomegaly aggressive snake or a snake of unknown disposition and other masses. Contrast studies are useful in should be identified and restrained before opening the diagnosing intestinal obstruction and constipation. In transportation bag and removing the animal. Venomous addition, contrast material in the gastrointestinal tract snakes should be anesthetized prior to physical contact. can often outline and help determine the origin of a non- In general, the head of the snake is held behind the specific intracoelomic masses; intraluminal or occiput using the thumb and middle finger to support the extraluminal. Cardiomyopathy has been reported in lateral aspects of the cranium. The index finger is placed snakes, which can be indicated by cardiomegaly on on top of the head. The other hand is used to support radiographs. Metastatic mineralization of large blood the serpentine body. Larger pythons and anacondas are vessels is often apparent around the heart due to the powerful and potentially dangerous. When dealing with negative contrast afforded by the adjacent lung(s). The large, even docile boids, a second, third, or even fourth superimposition of other organs such as liver and handler will be required to help control the body during stomach over the lung fields can make the radiographic the examination. It is usually safer and more convenient interpretation of respiratory disease challenging. to sedate a large pugnacious snake than to struggle on Common indications for evaluating the respiratory and risk injury to the snake, client, or staff. A complete system are rhinitis, suspected neoplastic and infectious physical examination should be performed, starting if disorders of the trachea and lung, as well as abscesses possible, with a hands-off approach to assess mentation or granulomas. The kidneys are not always and resting respiratory rate. The physical examination radiographically evident, unless enlarged or mineralized. should start with a resting heart rate and be followed by Disease processes that can cause renomegaly include an evaluation of neurologic function, muscle tone and renal gout and neoplasia. Eggs of oviparous species are strength, integument, infra-orbital pits (where present), leathery and poorly calcified, but can often be nostrils, eyes, oral cavity, and cloaca. The entire head, appreciated on plain radiographs. In viviparous species body and tail should be palpated, and any internal fetal skeletons become visible as they mineralize late in abnormalities recorded as a percentage or fraction of gestation. The hemipenes of some species may appear snout-to-vent length. The gender should be determined mineralized and can be detected radiographically.

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Common indications for evaluating the reproductive The caudal (tail) is accessed caudal to the system include dystocia, apparent infertility and reduced cloaca, between 25 and 50% down the tail. It is wise to fecundity. The presence of any swelling is an indication avoid the paired hemipenes of males (that may extend for radiography. Abscesses, which can either be up to 14 to 16 subcaudal scales caudal from the vent), extracoelomic or intracoelomic and associated with a and the paired cloacal musk glands of both sexes (that specific organ or the coelomic wall are common findings may extend up to 5 subcaudal scales). The needle is in snakes. angled at 45 to 60 degrees and positioned in the ventral Ultrasonography is particularly useful for evaluation mid line. The needle is advanced in a craniodorsal of soft tissues, especially the reproductive system, liver, direction, while maintaining slight negative pressure. If and kidneys. Copious gel (or a water bath) is required to the needle touches a vertebral body it is withdrawn reduce artifact caused by air trapped under the scales. slightly and redirected more cranially or caudally. This CT and MRI are used rarely, on a case by case basis. vessel is most easily entered in larger snakes and lymphatic contamination is possible but generally BLOOD uncommon. The ability to collect quality blood samples is With the snake restrained in dorsal recumbency, the essential in any animal class. Complete or selective heart is located approximately 22% to 33% from snout to hematologic and biochemical evaluations are possible vent. The heart is palpated and immobilized. The needle but the accuracy of results is often adversely affected by is advanced at 45 degrees in a craniodorsal direction poor venipuncture, handling or laboratory skills. The into the apex of the beating ventricle. Blood often enters production of poor quality blood data can be useless or the with each heartbeat. It is wise to maintain even worse, misleading to the clinician. Likewise, the digital pressure for 30 to 60 seconds following this ability to administer intravenous medications, especially technique. This technique has been employed in snakes anesthetics, or place intravenous catheters also relies on of all sizes from 10 g neonates to 100+kg constrictors. proficient veniclysis technique. Venipuncture is generally Nevertheless, good chemical/physical restraint is a blind technique in snakes. Despite a continuous trickle essential if significant cardiac trauma is to be avoided. of published blood ranges, there is still a relative dearth of hematologic or biochemical data for reptiles compared INTEGUMENT to domesticated animals. In addition, blood values can Dermatologic disease is a frequent presentation and vary dramatically with species, environment, nutrition, there are various levels at which the clinician can age, breeding status, hibernation and disease status. intervene and collect biological samples. Shed skin, skin Given this variability published ranges may be of limited scrapes, impression smears, scale and skin biopsies can value. More reliance should be placed upon establishing all be collected. The skin and associated structures are an individual's observed range and using serial perhaps the easiest to sample for laboratory analysis to monitor the progress of hematologic and biochemical due to their accessibility. However, they can also be the changes rather than relying on a single result. The two most demanding to interpret as contamination and common sites for venipuncture in snakes are the caudal secondary changes often mask the underlying primary (ventral tail) vein and the heart (Figure 1). complaint. Various ectoparasites may be clearly seen on

Figure 1. (a) Blood collection from the caudal (ventral tail) vein of a Boa constrictor – note the venipuncture site is in the ventral midline and caudal to the cloaca (arrow). (b) Dorsoventral radiograph of a corn snake following a barium enema – note the outline of a caudal mass, external to the intestinal tract. This well demarked and encapsulated mass was surgically excised, and proved to be a granulosa cell tumor

1753 NAVC Conference 2008 ______

Figure 2. (a) Shed skin from a snake that was suffering from severe mite infestation and self-inflicted wounds from the intense pruritus. One of these lesions can be appreciated from the abnormal slough (arrow). Insert, the common snake mite, Ophionyssus natricis, was recovered from the shed skin. (b) Endoscopic view of a Ball python (Python regius) with granulomatous pneumonia (arrow). The diagnosis of pulmonary mycobacteriosis was made following biopsy as lung lavage proved unrewarding.

the surface of the skin, around nostrils, eyes, and skin requires anesthesia and surgical or endoscopic folds (Figure 2). Mites, ticks, lice, maggots, flies can techniques. The upper respiratory tract including the often be physically removed and submitted in specimen nares, buccal cavity, glottis and cranial trachea can be containers for taxonomic identification. The shed skin of visualized and often sampled directly without anesthesia. reptiles is also a valuable asset and should be inspected Small diameter swabs permit the collection of samples, for evidence of parasitism. Suspected mites can be although the greatest concern comes from bacterial collected direct from the snake using a wet cotton-tipped contamination by oral commensals. Swabs can be applicator, and transferred to a microscope slide for submitted for microbiology or rolled onto glass slides for closer inspection and identification. Skin lesions are best staining and cytologic evaluation. The simplest method cleaned and partially debrided using aseptic techniques of obtaining a representative sample from the lower prior to the collection of clinical samples. Microbiologic respiratory tract is by lavage. Although a lung wash or swabs should be taken from the periphery of the lesion lavage can be carried out in the conscious reptile, the but deep to any exposed areas. Impression smears can discomfort of such a procedure probably warrants some be taken after the lesion has been cleaned with sterile degree of sedation or light anesthesia. A sterile catheter saline and gently dabbed dry with sterile gauze. Skin of appropriate size is placed through the glottis (or better scrapes may be useful especially when dealing with drier still through a sterile endotracheal tube pre-placed into more proliferative lesions. Where the clinician requires a the trachea) taking great care not to touch the oral skin biopsy the removal of a single scale may be all that membranes. The catheter is advanced caudal to the is required as scales contain both epidermal and dermal heart (>30% snout-vent) but in large specimens it may elements. A small volume (0.02–0.1 mL) of local not be possible to reach the lung(s) and a tracheal anesthetic (eg, 2% ) is injected subcutaneously lavage is performed. Once in place, 0.5 to 1.0 mL of in the area(s) of interest. Using aseptic techniques a sterile saline per 100 g bodyweight can be infused. single scale is then elevated and cut close to its insertion Sample recovery is often aided by rotating the snake, into the skin using a scalpel blade. If a larger sample is and lifting the head and tail to accumulate fluid at the required then a combination of local, regional or general dependent area, near the catheter tip. anesthesia and sharp excision or a skin punch biopsy Lavage samples do not permit an appreciation of instrument is effective. A single suture closes the deficit. lung architecture. For this, and many other histopathologic exams, tissue biopsies are preferred. RESPIRATORY SYSTEM Surgical access to the lung can be achieved using a The ability to diagnose pathologic changes within the standard coeliotomy or transcutaneous pulmonoscopy. respiratory system of snakes is often straightforward In snakes, the respiratory active anterior part of the lung following lung lavage for the collection of cytologic and is typically located between 12% and 45% snout-vent. microbiologic samples. The collection of tissue biopsies However there is great species variation with regards to

1754 Exotics – Reptiles ______lung anatomy including the presence of a tracheal lung For the collection of gastric or intestinal biopsies, in some elapids and viperids, both left and right lungs in standard coeliotomy and excisional biopsies can be boids, and only a right lung in most other snakes. undertaken but endoscopy is much less invasive. In snakes the small intestine can be readily entered via the GASTROINTESTINAL SYSTEM gastric pylorus. It is unwise to endoscopically biopsy the In cases of severe diarrhea or regurgitation, material large bowel as the intestinal wall is often thin and easily for laboratory submission will be forthcoming and may perforated. Even excisional biopsies of the large be collected and presented along with the animal by well intestine can be challenging to ensure adequate closure educated owners or keepers. In addition, many reptiles and the prevention of leakage. will spontaneously defecate and urinate when handled during the examination process. It is important to URINALYSIS appreciate that, like birds, the stools of reptiles are The clinician may assess the osmoregulatory system composed of fecal, urate and urine components and that of reptiles by sampling urine and biopsies from the the cloaca is a common chamber for the gastro- kidney. Urinalysis is less helpful in reptiles than intestinal, urinary and reproductive systems. For mammals. The reptilian kidney cannot concentrate urine example, watery stools due to polyuria must be and so urine specific gravity is of limited use in the differentiated from true diarrhea, and cloacal bleeding assessment of renal function. Furthermore, renal urine may be intestinal, reproductive or urinary in origin. Fecal passes through the urodeum of the cloaca before material can be submitted for a variety of parasitologic, entering the posterior colon. Urine is therefore not cytologic and microbiologic tests. The submission of only necessarily sterile. The clinical picture is further fecal material in appropriate sterile containers will complicated by the fact that electrolyte and water prevent further mixing and contamination by urates and changes can occur across the cloacocolonic mucosa. urine during transportation and processing. Microbiologic Despite these biochemical drawbacks, urine samples results from deposited feces should be interpreted with are useful for cytological assessments of inflammation, caution as contamination from other organ systems can infection, and for the identification of renal casts. occur in the cloacal proctodeum prior to elimination, while environmental contamination invariably occurs REPRODUCTIVE SYSTEM after elimination. The fresher the material, the more The advent of minimally invasive endoscopic meaningful the laboratory results, although some techniques has brought about an increase in urogenital parasitologic investigations (eg, helminth egg evaluation and sampling. The rigid endoscope can be examination) can be performed on refrigerated material used to examine the cloaca and, if patent, the oviducts up to 4 weeks or more after elimination. of female snake enabling the collection of exudates and Unfortunately, the slow intestinal transit times of most retained egg material in some cases. reptiles often necessitate a more direct approach to obtain material. A cloacocolonic lavage can be COELOMIC VISCERA performed on most conscious reptiles and provides the Visceral biopsy remains a powerful tool for clinician with a diagnostic sample. A sterile lubricated conclusively reaching a diagnosis, indicating specific round-tipped catheter is inserted into the cloaca and therapies and providing a more accurate prognosis. Fine cranially towards the colon. A relatively large catheter needle aspirates are generally poorly diagnostic should be used as this helps prevent kinking of the tube compared to tissue samples. Biopsies may be collected and perforation of the thin intestinal wall. On no account for histopathology and microbiology. Samples may be should the catheter be forced. Once in place, 0.5 to 1.0 collected percutaneously (generally with ultrasound mL sterile saline per 100 g bodyweight should be gently guidance from large organs like the liver), surgically (all infused through the catheter and repeatedly aspirated organs), or endoscopically (all organs). Correlation until a sample is obtained. It is possible to infuse an between biochemical tests and histopathology are additional 1.0 mL/100 g if no sample is forthcoming. The generally lacking but serial blood sampling and biopsy direct collection of fecal material from the distal colon currently offers the best diagnostic and monitoring using a lubricated gloved hand offers another practical approach to hepatic disease. option in large boids. A similar technique can be used to collect samples Liver Biopsy from the stomach. A relatively large, round-tipped Blood biochemistry, radiography, ultrasonography catheter can be inserted into the stomach of most and endoscopy may indicate the existence of a conscious reptiles. The catheter should pass to the mid- hepatopathy but they seldom provide the definitive body region before instilling 0.5 to 1.0 mL sterile saline diagnosis. The elongated liver of snakes is seldom per 100 g bodyweight. Such samples can be examined totally visible from a single coeliotomy approach. as a fresh wet preparation for parasites or stained to Biopsies are best collected using ligation or wedge demonstrate micro-organisms. Microbiologic cultures are techniques to avoid post-biopsy hemorrhage. often worthy but care is required in their interpretation as Endoscopic techniques are typically less invasive, permit contamination from the respiratory system and oral closer examination of more of the organ and enable the cavity is possible. collection of multiple biopsies

1755 NAVC Conference 2008 ______

Figure 3. (a) Renal biopsy of a Boa constrictor following standard coeliotomy. In this case, vascular Hemoclips have been used to isolate a small kidney lobule prior to sharp excision. (b) Cloacocolonic internal examination in a large python using a lubricated gloved .

Renal Biopsy collected by using suture or vascular clips to isolate a A variety of infectious, degenerative and neoplastic renal lobule. Snake endoscopy is more difficult that in renal diseases have been reported in snakes. The poor chelonians or lizards due to the multiple fascial planes regenerative capabilities of the kidney make early that have to be negotiated to reach the kidneys. diagnosis essential. The relatively poor diagnostic value However, evaluation of size, color and shape of the of urinalysis and the late detection of renal disease by kidneys via smaller surgical entry is possible, and blood biochemistry further exemplify the importance of permits the collection of multiple small biopsies. functional renal assessments and renal biopsy early in the diagnostic process (Figure 3). A standard coeliotomy REFERENCES between 85% and 95% snout-vent-length will generally 1. Mader DR. Reptile Medicine and Surgery. access the kidneys, although ultrasonographic Philadelphia, WB Saunders, 2006. localization of the kidneys preoperatively is 2. Raiti P, Girling S. Manual of Reptiles, British Small recommended to ensure surgical access where the left Animal Veterinary Association, Cheltenham, and right kidneys overlap. Excisional biopsies are easily England, 2004.

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