History. A 4-year-old, intact male green iguana (Iguana iguana) was presented with a 2-day history of lethargy and anorexia. It roamed free in the client's house. A basking lamp was situated in one room, the temperature of which was approximately 85ºF. The iguana would bask under it periodically. Ambient temperature was 74ºF; environmental humidity was not measured. Dark, leafy greens, including romaine lettuce, mustard and collard greens, and occasionally green beans, broccoli, kale, and spinach comprised the diet. No supplements were offered. Free-choice water was offered from a large plastic bowl. The owner also soaked the iguana in the bathtub once a week for 30 minutes. The only other pet in the household was a cat. There was little interaction between the two animals, but the iguana was observed eating the cat's food. No other illnesses in the 4 years the client owned the animal were reported, and this was the first time it was presented to a veterinarian.
Physical examination. The iguana weighed 1.2 kg and had a body condition score of 2/5. It was depressed, weak, and had a bronze coloration.
Muscle wasting was evident in the limbs and over the spine and pelvis. Muscle fasciculations were noted in the biceps, triceps, and quadriceps. Mucous membranes were pale and tacky. Two large masses were palpated in the caudal coelomic cavity. Digital cloacal palpation indicated that the coelomic masses originated from within the pelvic canal. Heart and respiratory rates were normal.
ASK YOURSELF . . .
• What are the problems identified from the history, physical examination, and diagnostic tests?
• What is your primary differential at this time?
• What further diagnostics would you perform?
Diagnosis. Chronic renal disease. The masses were the kidneys, which in green iguanas are normally situated in the dorsal pelvic canal. With renomegaly, the cranial poles extend over the pelvic brim. Biopsy is required to confirm renal disease.
Several techniques may be used to collect renal biopsies. The percutaneous technique and endoscopy are least invasive. Cranial tail cut-down and coeliotomy are more invasive but do not require expensive equipment, as does endoscopy. Each technique limits the area from which one can collect the sample -cranial pole (percutaneous, endoscopy, coeliotomy) or caudal pole (cranial tail cut-down). With focal pathology, histopathologic samples may be unremarkable. Several biopsies must be collected to increase the likelihood of characterizing the condition. In this case, the author performed coeliotomy and histopathologic findings were consistent with glomerulonephrosis. Recovery from surgery was uneventful.
The weakness, lethargy, and muscle fasciculations were attributed to plasma calcium levels far below reference range. Unfortunately, the author was unable to characterize the ionic calcium levels. Muscle fasciculations would be expected to increase as ionic calcium levels decrease. Cardiac arrhythmia and arrest might also be expected in cases of dangerously low levels of ionic calcium. Although the packed cell volume was within the reference range, the author felt the animal was 5% dehydrated based on clinical signs (e.g., tacky mucous membranes). The elevated creatine kinase and aspartate transaminase were attributed to muscle necrosis. Hypoprotein-
emia and hypoalbuminemia were attributed to passive excretion at the renal level.
Interpreting urinalysis in reptiles can be difficult. Because they lack the loop of Henle, for example, urine does not concentrate; so the specific gravity is often isosthenuric. Also, urine enters the cloaca before the urinary bladder (chelonians and lizards); therefore, most urine samples are contaminated with gastrointestinal microbes. However, renal casts were identified in this sample, suggesting renal disease.
Characterizing chronic renal disease in green iguanas is very difficult. Chronic dehydration, hypervitaminosis D, high-protein diets, bacterial infection, and neoplasia have all been implicated. In this particular case, the environmental temperature was inappropriate, possibly causing physiologic and osmotic disturbances, and the cat food could have contributed to the renal disease. Iguanas may not be able to process and excrete
certain components of a carnivorous diet (vitamin D and purines) without physiologic damage.
DID YOU ANSWER. . .
History/physical examination: lethargy, anorexia, inappropriate environmental temperature/humidity, free-roam of house and soaking in bathtub, (foreign body ingestion, public health concern of Salmonella), eating cat food, two caudal coelomic masses, depression/weakness, muscle wasting, fair body condition, muscle fasciculations, pale/tacky mucous membranes
• plasma chemistry analysis: hypocalcemia, hyperphosphatemia, hypoproteinemia, hypoalbuminemia, elevated AST and CK
• CBC: hemoconcentration
• urinalysis: renal casts
• radiographs: renomegaly
Chronic renal disease
Renal biopsy to collect a sample for histopathologic testing; ultrasonography could also be done but would probably offer no information on the underlying cause of renal disease.
TX ... at a glance
• Warmed isotonic fluids (30 ml/kg/ day intracoelomically) for 7 days
• Phosphate binder (calcium carbonate, 250 mg/kg, PO q 24h)
• Force-feed enteral herbivore diet.
• On discharge, restrict habitat, maintain environmental temperature of 85-100ºF, and preclude access to inappropriate food.