RENAL EVALUATION IN THE HEALTHY GREEN IGUANA (IGUANA IGUANA): ASSESSMENT OF PLASMA BIOCHEMISTRY, GLOMERULAR FILTRATION RATE, AND ENDOSCOPIC BIOPSY

CLINICAL AND PATHOLOGIC FINDINGS IN IGUANIDS WITH SODIUM URATE CHOLELITHIASIS

Four green iguanas (Iguana iguana) and one blue iguana (Cyclura lewisi) from five facilities were diagnosed with sodium urate cholelithiasis. One case was diagnosed antemortem via ultrasonography, and the iguana underwent a choledochotomy for treatment. The other four cases were identified at necropsy. Pathologic hepatic and biliary changes were present in four of the five cases at necropsy. Histologically, four iguanas had hepatic fibrosis, three had bile duct hyperplasia, and one had cholangiohepatitis and pancreaticocholedochitis. Two iguanas had pathologic renal changes. This is the first report of sodium urate cholelithiasis in reptiles. This case series highlights the potential significant clinical disease caused by sodium urate cholelithiasis and the importance of biliary system evaluation. Further investigation is recommended to explore the pathogenesis of reptilian sodium urate cholelith formation.

Effects of the environment on the evolution of the vertebrate urinary tract

Evolution of the vertebrate urinary system occurs in response to numerous selective pressures, which have been incompletely characterized. Developing research into urinary evolution led to the occurrence of clinical applications and insights in paediatric urology, reproductive medicine, urolithiasis and other domains. Each nephron segment and urinary organ has functions that can be contextualized within an evolutionary framework. For example, the structure and function of the glomerulus and proximal tubule are highly conserved, enabling blood cells and proteins to be retained, and facilitating the elimination of oceanic Ca+ and Mg+. Urea emerged as an osmotic mediator during evolution, as cells of large organisms required increased precision in the internal regulation of salinity and solutes. As the first vertebrates moved from water to land, acid-base regulation was shifted from gills to skin and kidneys in amphibians. In reptiles and birds, solute regulation no longer occurred through the skin but through nasal salt glands and post-renally, within the cloaca and the rectum. In placental mammals, nasal salt glands are absent and the rectum and urinary tracts became separate, which limited post-renal urine concentration and led to the necessity of a kidney capable of high urine concentration. Considering the evolutionary and environmental selective pressures that have contributed to renal evolution can help to gain an increased understanding of renal physiology.

Urine Output Monitoring and Acute Kidney Injury in Non-mammalian Exotic Animal Critical Care

Acute kidney injury (AKI) is a sudden, severe decrease in kidney function which can occur in any species. There are various causes of AKI, some of which are seen in domestic species and some that are unique to birds, reptiles, and amphibians. These species present unique challenges with AKI management, such as differences in anatomy and physiology, intravenous and urinary catheterization, repeated blood sampling, and their tendency to present in advanced states of illness. This article will discuss AKI, diagnosis, treatment, and prognosis for non-mammalian exotic species.

Retrospective evaluation of intravenous catheterization in client-owned lizards at a veterinary teaching hospital: 21 cases (2018-2021)

OBJECTIVE

To assess the prevalence of lizards presenting to a university teaching hospital that had an IV catheter placed, the catheterization sites used, and complications arising with the placement of the catheter both in the short and long term.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Twenty-one lizards, including inland bearded dragons (Pogona vitticeps; 15/21), green iguanas (Iguana iguana; 4/21), and veiled chameleons (Chamaeleo calyptratus; 2/21).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 129 lizard consultations performed between September 27, 2018 and September 27, 2021, 21 catheters were placed, resulting in an overall prevalence of 16.3%. Reasons for catheter placement included hospitalization for fluid therapy (10/21 [47.6%]), anesthesia or surgery ± hospitalization (7/21 [33.3%]), computed tomography scan with contrast (2/21 [9.5%]), euthanasia only (1/21 [4.8%]), and CPR only (1/21 [4.8%]). All catheters were placed in the ventral coccygeal vein via a ventral approach. Sedation was used in 6 of 21 (28.6%) of the catheters placed. Seven of the catheters (35%) were used for administration of fluids only, 4 (20%) were used for administering drugs/medications only, and 9 (45%) catheters administered both fluids and drugs/medications. No complications were noticed in any of the lizards that had catheters placed, both in the short and long term.

CONCLUSIONS

Based on the retrospective evaluation of medical records at a veterinary teaching hospital, IV catheter placement in lizards is feasible, including in conscious animals, with roughly 1 consultation out of 6 resulting in a catheter placed. The most frequent reason for catheter placement was for administration of fluids.

[Diagnosis of kidney diseases in European tortoises (Testudo spp.)]

The diagnosis of kidney diseases in tortoises is only possible to a very limited extent on the basis of the general examination due to the development of unspecific disease symptoms. Extensive additional examinations are required to confirm the diagnosis. In addition to blood and urine tests, imaging techniques such as X-ray, computed tomography and MRI are suitable for visualizing the skeletal and organ systems, while additional samples can be taken during an endoscopic examination. There are clear species-specific differences with regard to the reference values of the laboratory parameters, which are in part significantly influenced by environmental influences, the seasons or even gender. It can also be seen that kidney diseases in tortoises kept in captivity are usually very advanced at the time of diagnosis, since these animals, like reptiles in general, show a pronounced lack of symptoms. Annual checks by a veterinarian specialized in reptiles can help to detect diseases at an early stage.

Conservation of a flagship species: Health assessment of the pink land iguana, Conolophus marthae

The pink land iguana, Conolophus marthae, is one of four species of iguanas (three terrestrial and one marine) in the Galápagos Islands, and the only one listed as critically endangered by the IUCN. The species can only be found on the north-west slopes of the highest volcano on Isabela Island and was first described to science in 2009. As part of a population telemetry study, a health assessment was authorized by the Galápagos National Park. Wild adult iguanas were captured on Wolf Volcano in September 2019 and April 2021 to record morphological and physiological parameters including body temperature, heart rate, intraocular pressures, tear formation, and infrared iris images. Blood samples were also collected and analyzed. An i-STAT portable blood analyzer was used to obtain values for base excess in the extracellular fluid compartment (BEecf), glucose (Glu), hematocrit (HctPCV), hemoglobin (Hb), ionized calcium (iCa), partial pressure of carbon dioxide (pCO₂), partial pressure of oxygen (pO₂)_, percent oxygen saturation (sO₂%), pH, potassium (K), and sodium (Na). When possible, data were compared to previously published and available data for the other Galápagos iguanas. The results reported here provide baseline values that will be useful in detecting changes in health status among pink land iguanas affected by climate change, invasive species, anthropogenic threats, or natural disturbances. The collected data also provide an invaluable resource for conservation scientists planning to implement conservation strategies, like translocations, that may temporarily alter these baseline values.

Clinical Management of Reptile Renal Disease

Renal disease is one of the most common medical conditions encountered in captive reptiles. In most cases, signs of disease are nonspecific and often not present until the condition is advanced. Many factors contribute to the development of renal disease, and the etiology often is multifactorial. Diagnosis of renal disease by traditional methods used in small animals is not as straightforward as in reptiles; often many tests may be needed to reach a firm diagnosis. Prevention is preferred to treatment. Understanding the pathophysiology, potential causes, diagnostic tests available, and treatment options is essential for the reptile veterinarian to manage this condition.

Diagnostic Imaging of the Reptile Urinary System

Reptiles can develop various diseases of the urinary tract, including, but not exclusively, urolithiasis, gout, acute and chronic kidney injury, and secondary renal hyperparathyroidism. Diagnostic imaging is instrumental in differentiating and diagnosing these ailments. This article describes the current diagnostic imaging approaches used in reptile medicine for evaluation of urinary tract disease. The use of radiographs, ultrasonography, computed tomography, MRI, and endoscopy is discussed and compared for the evaluation of urinary tract disease in reptiles.

Health assessment of Conolophus subcristatus, Conolophus pallidus, and C. subcristatus X Amblyrhynchus cristatus hybrid (Galápagos land iguanas)

The land iguanas, Conolophus pallidus and Conolophus subcristatu are large and charismatic lizards endemic to the Galápagos archipelago, but little information exists on their normal health parameters. The former is restricted to Santa Fe island, while C. subcristatus inhabits the islands of the central and western region of the archipelago. Both species are classified as vulnerable by the IUCN Red List of Threatened Species. As part of a population health assessment authorized by the Galápagos National Park, wild adult iguanas from three islands (North Seymour, South Plazas, and Santa Fe) were captured in July 2018. Data from a single C. subcristatus X Amblyrhynchus cristatus hybrid captured on South Plazas is also included. We analyzed blood samples drawn from 52 healthy wild adult land iguanas captured on three islands. An iSTAT portable blood analyzer was used to obtain values for pH, lactate, pO2, pCO2, HCO3-, sO2%, hematocrit, packed cell volume (PCV), hemoglobin Na, K, iCa, and glucose. Standard laboratory hematology techniques were employed for PCV determination; resulting values were also compared to the hematocrit values generated by the iSTAT. Body temperature, heart rate, respiratory rate, and body measurements were also recorded and compared to previously published data for the marine iguana (Amblyrhynchus cristatus), which shares a common ancestor with the land iguana. The data reported here provide preliminary baseline values that may be useful in comparisons between captive and wild populations, between wild populations, and in detecting changes in health status among Galápagos land iguanas affected by anthropogenic threats, climate change, or natural disturbances.

Reptile Soft Tissue Surgery

The surgical approach to reptiles can be challenging. Reptiles have unique physiologic, anatomic, and pathologic differences. This may result in frustrating surgical experiences. However, recent investigations provided novel, less invasive, surgical techniques. The purpose of this review was to describe the technical aspects behind soft tissue surgical techniques that have been used in reptiles, so as to provide a general guideline for veterinarians working with reptiles.

Blood gases, biochemistry and haematology of Galápagos marine iguanas (Amblyrhynchus cristatus)

The marine iguana, Amblyrhynchus cristatus, is an iconic lizard endemic to the Galápagos Islands of Ecuador, but surprisingly little information exists on baseline health parameters for this species. We analysed blood samples drawn from 35 marine iguanas captured at three locations on San Cristóbal Island. A portable blood analyser (iSTAT) was used to obtain near-immediate field results for pH, lactate, partial pressure of O2, partial pressure of CO2, bicarbonate (HCO3 (-)), percentage O2 saturation, haematocrit, haemoglobin, sodium, potassium, ionized calcium and glucose. Parameter values affected by temperature were auto-corrected by the iSTAT. Standard laboratory haematology techniques were employed for differential white blood cell counts and haematocrit determination; resulting values were also compared with the haematocrit values generated by the iSTAT. Body temperature, heart rate, respiratory rate and body measurements were also recorded. Body length was positively correlated with several blood chemistry values (HCO3 (-) and glucose) and two haematology parameters (haemoglobin and manually determined haematocrit). A notable finding was the unusually high blood sodium level; the mean value of 178 mg/dl is among the highest known for any reptile. This value is likely to be a conservative estimate because some samples exceeded the maximal value the iSTAT can detect. For haematocrit determination, the iSTAT blood analyser yielded results significantly lower than those obtained with high-speed centrifugation. The values reported in this study provide baseline data that may be useful in comparisons among populations and in detecting changes in health status among marine iguanas affected by natural disturbances or anthropogenic threats. The findings might also be helpful in future efforts to demonstrate associations between specific biochemical parameters and disease.

Incomplete ovariosalpingectomy and subsequent malignant granulosa cell tumor in a female green iguana (Iguana iguana)

CASE DESCRIPTION

A 9-year-old spayed female green iguana (Iguana iguana) was evaluated because of a distended coelom and weight loss. History included a single episode of egg binding and subsequent bilateral ovariosalpingectomy.

CLINICAL FINDINGS

Physical examination revealed a mass within the coelomic cavity. Ultrasonography revealed a large, irregular mass with hypoechoic regions and coelomic effusion. Clinicopathologic derangements included heterophilia, monocytosis, lymphopenia, basophilia, hypocholesterolemia, hypoproteinemia, and hypercalcemia. Results of cytologic evaluation of the mass were suggestive of malignant epithelial neoplasia, but neoplastic cells were not found in the effusion. An ovarian tumor was suspected on the basis of clinical signs, clinicopathologic findings, and results of cytologic evaluation of the mass.

TREATMENT AND OUTCOME

Surgical exploration revealed a large left ovary, a normal-appearing contralateral ovary, and a mass in the fat body, all of which were removed and submitted for histologic examination. The histologic diagnosis was granulosa cell tumor with metastasis to the fat body. The patient died 11 months after evaluation, and disseminated granulosa cell tumor was confirmed at necropsy; histologic examination at that time also identified systemic mastocytosis.

CLINICAL RELEVANCE

Granulosa cell tumors are uncommon in reptiles, and this was the first granulosa cell tumor described antemortem cytologically, histologically, and ultrastructurally in an iguana. Findings in this iguana underscored concerns associated with incomplete oophorectomy of iguanas; cytologic and histopathologic findings were similar to those observed in other domestic animals. Oophorectomy should be considered as an alternative to standard ovariosalpingectomy to avoid potential complications in pet reptiles, and use of microsurgical instruments and vascular clips is advised.

Pollutants and the health of green sea turtles resident to an urbanized estuary in San Diego, CA

Rapid expansion of coastal anthropogenic development means that critical foraging and developmental habitats often occur near highly polluted and urbanized environments. Although coastal contamination is widespread, the impact this has on long-lived vertebrates like the green turtle (Chelonia mydas) is unclear because traditional experimental methods cannot be applied. We coupled minimally invasive sampling techniques with health assessments to quantify contaminant patterns in a population of green turtles resident to San Diego Bay, CA, a highly urbanized and contaminated estuary. Several chemicals were correlated with turtle size, suggesting possible differences in physiological processes or habitat utilization between life stages. With the exception of mercury, higher concentrations of carapace metals as well as 4,4'-dichlorodiphenyldichloroethylene (DDE) and γ chlordane in blood plasma relative to other sea turtle studies raises important questions about the chemical risks to turtles resident to San Diego Bay. Mercury concentrations exceeded immune function no-effects thresholds and increased carapace metal loads were correlated with higher levels of multiple health markers. These results indicate immunological and physiological effects studies are needed in this population. Our results give insight into the potential conservation risk contaminants pose to sea turtles inhabiting this contaminated coastal habitat, and highlight the need to better manage and mitigate contaminant exposure in San Diego Bay.

Evaluation of diagnostic coelioscopy including liver and kidney biopsy in freshwater turtles (Trachemys scripta)

The objective of this study was to establish a safe and effective endoscopic technique for the examination of coelomic viscera and for the collection of liver and kidney biopsy specimens from turtles by use of a 2.7-mm rigid endoscopy system that is commonly available in zoologic veterinary practice. Twenty-two adult freshwater turtles (Trachemys scripta) were anesthetized for both left and right coelioscopic examinations. Ease of entry and organ visualization were scored, and liver and kidney biopsy specimens were collected from each turtle by use of 1.7-mm endoscopic biopsy forceps. Biopsy samples were evaluated histologically for quality and crush artifact. Five days after surgery, all turtles were euthanatized and underwent full necropsy examination. For all 22 turtles, left and right mean entry and visualization scores were satisfactory to excellent for all measured parameters except spleen because the spleen was impossible to locate from the left side. No iatrogenic trauma was evident, and biopsy specimens were consistent with tissues collected at necropsy. Liver biopsies suffered from greater crush artifact, compared with kidney biopsies. By use of a 2.7-mm rigid endoscopy system, coelioscopy, liver and kidney biopsy procedures can be performed safely, swiftly, and with ease in turtles. Biopsy specimens obtained by this technique are suitable for histologic examination. Endoscopy is recommended for the examination and biopsy of coelomic viscera in chelonians.

A fresh look at metabolic bone diseases in reptiles and amphibians

Metabolic bone diseases (MBDs) are a common presenting complaint in reptiles and amphibians to veterinarians; however, understanding of the causes and diagnostic and treatment options is often extrapolated from human or other mammalian medicine models. Although the roles of UV-B, calcium, phosphorus, and cholecalciferol are better understood in some MBDs, there remain many X factors that are not. Likewise, quantitative diagnosis of MBDs has been difficult not only in terms of staging a disease but also regarding whether or not a condition is present. Treatment options also present challenges in corrective husbandry and diet modifications, medication/modality selection, and dosing/regimen parameters.

Reptile diagnostic endoscopy and endosurgery

The 2.7-mm telescope commonly used in avian practice has transitioned into an invaluable diagnostic tool for the reptile clinician. Previously plagued by vague medical histories, nonpathognomonic physical examinations, indistinct diagnostic images, and less than conclusive clinical pathology results, the reptile clinician often has had trouble making a definitive, antemortem diagnosis. A definitive diagnosis generally relies on the demonstration of a host pathologic response and the causative agent. The ability to examine internal structures and collect biopsies has enabled many postmortem diagnoses to now be appreciated in the living animal, and along with accurate diagnosis comes accurate prognosis and improved case management. The advent of 3-mm human pediatric laparoscopy equipment has fueled interest in minimally invasive endosurgery in exotic pets, including reptiles. However, the chelonian shell has also served as a catalyst to speed the development of surgical approaches to the coelom that do not involve major shell surgery. This article summarizes the most common endoscopic approaches in lizards, chelonians, and snakes for the purposes of making a diagnosis and increasingly performing endosurgery.

Comparative study of hematologic and plasma biochemical variables in Eastern Atlantic juvenile and adult nesting loggerhead sea turtles (Caretta caretta)

BACKGROUND

Plasma biochemical and hematologic variables are important in the management of endangered sea turtles, such as loggerheads. However, studies on blood biochemistry and hematology of loggerheads are limited, and different concentrations according to variable criteria have been reported.

OBJECTIVE

The purpose of this study was to establish and compare baseline plasma chemistry and hematology values in Eastern Atlantic juvenile and adult nesting loggerhead sea turtles (Caretta caretta).

METHODS

Blood samples were collected from 69 healthy juvenile loggerhead sea turtles after their rehabilitation in captivity, and from 34 adult nesting loggerheads after oviposition. Fresh blood was used for leukocyte differential count and PCV determination. Heparinized blood was used for RBC and WBC counts. Plasma biochemical concentrations were measured using an automated biochemical analyzer. For the comparative study, nonparametric statistical analysis was done using the Mann-Whitney U-test.

RESULTS

Minimum, maximum, and median concentrations were obtained for 14 hematologic and 15 plasma chemistry variables. Statistically significant differences between juvenile and adult turtles were found for PCV; RBC, WBC, and leukocyte differential counts; total protein, albumin, globulins, calcium, triglycerides, glucose, total cholesterol and urea concentrations; and lactate dehydrogenase activity.

CONCLUSIONS

Age, size, and reproductive status cause important variations in the hematologic and plasma biochemical results of loggerheads. The reference values obtained in this study may be used as a standard profile, useful for veterinary surgeons involved in sea turtle conservation.

Evaluation of an endoscopic liver biopsy technique in green iguanas

OBJECTIVE

To establish a safe and effective endoscopic technique for collection of liver biopsy specimens from lizards by use of a 2.7-mm rigid endoscope system that is commonly available in zoologic veterinary practice.

DESIGN

Prospective study.

ANIMALS

11 subadult male green iguanas (Iguana iguana).

PROCEDURES

Each lizard was anesthetized, and right-sided coelioscopic examination of the right liver lobe and gallbladder was performed. Three liver biopsy specimens were collected from each lizard by use of a 2.7-mm rigid endoscope and 1.7-mm (5-F) biopsy forceps. Biopsy samples were evaluated histologically for quality and crush artifact. Ten days following surgery, all iguanas were euthanatized and underwent full necropsy examination.

RESULTS

For all 11 iguanas, the right liver lobe and gallbladder were successfully examined endoscopically, and 3 biopsy specimens of the liver were collected without complications. Mean +/- SD durations of anesthesia and surgery were 24 +/- 7 minutes and 6.8 +/- 1.0 minutes, respectively. At necropsy, there was no evidence of trauma or disease associated with the skin or muscle entry sites, liver, or any visceral structures in any iguana. All 33 biopsy specimens were considered acceptable for histologic interpretation; in most samples, the extent of crush artifact was considered minimal.

CONCLUSIONS AND CLINICAL RELEVANCE

By use of a 2.7-mm rigid endoscope, liver biopsy procedures can be performed safely, swiftly, and easily in green iguanas. Biopsy specimens obtained by this technique are suitable for histologic examination. For evaluation of the liver and biopsy specimen collection in lizards, endoscopy is recommended.

Renal diseases of reptiles

Renal disease is one of the most common problems in reptilian medicine. Herbivorous species seem to be more susceptible than carnivores. The causation may be multifactorial, and the signs are often nonspecific. Prevention is preferred to treatment, and a comprehensive health program, which includes quarantine, routine health screens during annual examinations, and necropsy examinations of all animals that die, is desirable.