Melissa
Kaplan's
Herp Care Collection
Last updated
January 1, 2014
Kidney failure in green iguanas
©1996, 2002 Melissa Kaplan
What causes
kidney failure in iguanas? Are there any signs when an iguana's kidneys
are failing? Are they especially prone to this?
Iguanas
in captivity are prone to this in a large part because people keep feeding
them animal protein and do not give them enough access to water or humidity.
Books that say to feed animal protein and only put down water once a week
have not increased iguana longevity - quite the contrary: since the new
iguana books came out in the early 1990's, it appears that kidney failure
is striking at younger ages, with iguanas dying at 3-5 years rather that
7-9 years from it...and even that was far short of the 15-20+ years they
should be living.
Fed a proper plant-based diet, with regular access to water and spraying, iguana kidneys generally do just fine. With insufficient water, however, the kidneys have to strain to work. Add animal protein to such a 'dry' system, and the kidneys don't have a chance. The commercial food products of dry pellets or powders whose instructions state to feed dry are also likely to contribute to kidney problems, whether or not they have, as some do, animal protein in them.
Many antibiotics are hard on the kidneys, and need to be administered in conjunction with additional fluids (by injection) to try to prevent harmful effects on the kidneys. Since there have been no widespread pharmacokinetic studies on green iguanas or other reptiles (although, at this time, some are now underway) all drugs and dosages have been extrapolated from those used on mammals. While we will eventually know what is safe to use at what dosages, etc., for now it is still part guess, part experience, and part luck. In the meantime, antibiotics remain a potential cause of kidney problems.
When kidney failure occurs, its external signs--what you see--happens suddenly and the animal usually dies soon thereafter. Signs include anorexia, weight loss despite eating, lethargy, swollen or distended abdomen, frequent drinking or voiding, grossly swollen neck (not the normal jowls of the sexually mature male) and/or dewlap. Upon x-rays, kidneys, not normally visible due to their position in the pelvic area, may be seen protruding up into the coelomic cavity; they may also be felt. Many blood levels (BUN, creatinine, uric acid) may be within normal ranges, but phosphorous levels may be elevated and the calcium:phosphorous ratio may be way off, with calcium less than 1:1. Some iguanas may be mildly hypocalcemic (calcium deficient) while others may be hypercalcemic (excessive levels of calcium; see the article on hypercalcemia). Some may exhibit mineralization of the tissues due to the buildup of uric acid crystals (due to animal protein or lack of sufficient hydration to effect proper digestion and waste removal), which may be visible or felt as hard lumpy clusters around the joints of the legs and feet. Kidney biopsies and ultrasound may be beneficial in diagnosing the condition.
Treatment, if the condition is caught early enough, includes complete diet and environment overhaul, phosphate binders and hydration via IV or IO (intraosseous--in the bone) lines. Igs who survive one bout of renal disease will always be susceptible to it and must be watched carefully in the future.
"But,
my iguana was so healthy."
I cannot stress the following too strongly. Generally
speaking, right up until 1-2 weeks before they start to die--before their
kidneys give out for good--they are healthy looking, exhibiting normal
behaviors, thermoregulation, feeding, and defecating with normal looking
urates and feces. The symptoms of renal failure can come on so suddenly,
and overlap those of many other conditions, that most owners don't even
do anything about it until their iguana lapses into final shock. It is
in this last one-to-two week period that things start to happen, the altered
behavior; acting increasingly lethargic; the loss of appetite; rapid dehydration;
constipation; thickened and yellowing urates; reduced thermoregulation
or complete failure to thermoregulate (as they get too weak to move);
increased sleep time; extremely rapid weight loss (inconsistent with past
periods of reduced or no food intake); loss of muscle tone; lack of deep
pain responses; and gross reduction in interactive [animal/animal and
animal/human] responses.
"But
he's eaten animal protein for years and has been just fine."
You may have
been feeding your iguana animal protein for several years and it may be
looking and acting just great. So have all the iguanas who came to me
from such backgrounds, right up until they "crashed and burned"
within the week or two before their kidneys failed. My advice is to get
blood work done annually to monitor their kidney function and related
serum indicators on iguanas who have animal protein histories or to whom
you continue to feed protein if you insist on doing so.
Yes, there are a few iguanas out there who live into their 'teens cheerfully chowing down on animal protein every day. There are also a few three-pack a day cigarette smokers who live to a ripe old age and die of a disease unrelated to their smoking. Just as the latter is hardly justification for ignoring the deaths each year caused by smoking in primary and secondhand smokers, so too can iguana owners not ignore the findings in the recent reptile veterinary and biological literature. At least a smoker has a choice as to whether to risk his life and health. Iguanas in captivity do not truly have a choice, being at the mercy of their owners, and their owners' common sense and concern for them.
But
I've never fed him protein, dry food or monkey biscuits and still his
kidneys failed.
While iguanas have been kept in captivity for several
decades, it is only in the past handful of years that veterinarians even
started specializing in reptile and amphibian medicine, and so it is only
relatively recently that documentation has begun on iguana care and survival.
While being fed animal protein and chronic low levels of dehydration are
continuing problems facing iguanas. Reptile vets also recognize that other
factors may come into play. That these factors exist is brought home in
the cases of iguanas who have apparently been raised properly - no animal
protein, low fat diet, proper selection of plant foods, regular bathing
and humidified air - also develop and die from kidney failure.
A case in point is a marvelous 10 year old iguana belonging to a friend of mine. Hood had been raised on a healthy vegetable diet, got daily baths, proper heat, annual checkups by a top reptile vet, vet visits when he acted the least bit strange. Hood was highly tamed and socialized, relaxed when he was involved in education events. His owner had to leave town for a month, but left Hood at home with proper care by caretakers he knew. Shortly after the owner's return from his month away, he went away for a long weekend. Upon his return from that weekend he found Hood lethargic and saw that he had lost a great deal of weight since the last saw him three days before. The owner called his vet, who turned out to be out of the country. The vets to whom he was referred by that office were also unavailable. The owner began calling vet offices around town, but the vets were either out or the offices couldn't fit him in (which indicates vet staff need to be trained to recognize the possible signs of kidney failure and to treat these calls as emergencies and work them in!). He finally got into a vet 24 hours later. By that time Hood was extremely weak, had lost even more weight, was severely dehydrated, and not responsive. Despite aggressive fluid and antibiotic therapy, Hood did not respond, and did not survive the next 24 hours.
So, what happened? The necropsy showed that he was very healthy other than the kidneys. Could it have been his age? Maybe, but 10 years old really isn't that old in a species whose life span can range from 15-20+ years. Could the stress of the last couple of months, with the prolonged owner absence, have caused immune failure or some other systemic malfunction? It is well known that iguanas, even if cared for at home by a known caretaker (including the parent, spouse or live-in partner of the owner), react to their owner's absence, often getting depressed (lethargic, reduced appetite, significant alteration of regular daily routine) and acting out when the owner returns (breaking potty training, aggressive, snappy or whippy behavior). Might he not have been hydrated enough? Vet recommendations for humidity levels range from 60-100% humidity for several hours during the day (Hood was maintained at 60%).
What this tells us is that even if you do everything apparently right, the kidneys might still go. Rather than say, "what the heck" and go ahead and give our iguanas animal protein and keep them in desert-like environments, however, we must still provide the best diet and environment we can. In addition, we must be observant and proactive when they begin to show signs of illness, and whenever possible, have necropsies done in order to try to find out what happened.
I encourage everyone to do some research on their own. The research should not include pet trade books published before 1995 or so but should be focused on iguana biology and research, and care books reflecting such research. Veterinary and biological references may be found in my bibliography on iguanas, including John Iverson's Adaptation to Herbivory in Iguinine Lizards in the book by Burghardt and Rand, Iguanas of the World: Their Behavior, Ecology, and Conservation; the chapter on reptile nutrition by reptile vet and nutritionists Susan Donoghue in Douglas Mader's book Reptile Medicine and Surgery, and Jim Hatfield's book on iguana care. These sources also contain numerous citations that can be investigated as well. The Association of Reptile and Amphibian Veterinarian's quarterly bulletin may also be a useful source of information as new findings are published.
Captive iguanas, like all captive animals, should be living long and healthy lives, their age at death equaling or greater than the number of years they are expected to live in the wild. Theoretically, in captivity, the common causes of early death in wild animals are obviated as they are protected from predation, disease, and cyclical fluctuations in harsh weather conditions and scarce food resources. The fact that relatively young iguanas are dying by the tens of thousands every year is a clear signal that we haven't been doing it right, that we have been making some gross blunders in our understanding of their needs and functions. Continuing to rely on out-of-date pet trade resources, like the many TFH iguana books, pet store and outdated veterinary caresheets, and even many zoo diets out there, does a great disservice to your green iguana, a pet that should be a companion animal for many, many years...
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