Green iguana nephrology: a review of diagnostic techniques

There is still much to learn about renal physiology and pathophysiology in reptiles. In the case of the green iguana, initiating causes are often inferred from poor husbandry and nutrition, or extrapolated from histopathologic interpretations made late in the course of the disease, or at postmortem. The link between parathyroid hormone and renal disease in humans has been well documented and, given the high prevalence of clinical (and subclinical) secondary nutritional hyperparathyroidism in iguanas, this certainly warrants further investigation in saurians [31,32,34,35]. Apart from hyperparathyroidism, chronic water deprivation also appears to be a common historic factor. As a foliovore originating from the high humidity rain forests of central and South America, water recovery is not considered to be an adaptive stress in Iguana iguana, and therefore, renal anatomy and physiology are considered to be non-specialized compared to more arid or aquatic reptiles [21]. These arboreal lizards do not voluntarily drink from open water but instead imbibe rain or dew droplets from foliage [2]. Maintaining such a species in low relative humidity with a water bowl from which to drink is likely to both increase insensible water losses and interfere with normal water intake. Appropriate therapeutic decisions (including euthanasia) can only be made following an accurate diagnosis. To date, our diagnoses are based largely upon the structural evaluations of renal histopathology, and renal biopsy remains our most useful tool. However, in the future it may become possible to evaluate renal function by quantifying glomerular filtration rate, proximal tubular secretion, or functional renal mass. Glomerular filtration rate may be estimated by measuring the rate of glomerular clearance of substances from the blood (e.g., iohexol). Phenolsulphonphthalein assays may offer an insight into proximal tubule secretion and renal blood flow.