Swollen joint. Photo by Dr. Kathleen Cavell
Gout is excess amounts of uric acid in the blood. This excess can be the result of either overproduction of uric acid or the body’s failure to get rid of it. This excess uric acid gets deposited in tissues (visceral gout) or into joints (articular gout), causing a great amount of inflammation and pain. Pseudogout is similar to true gout, but is caused by deposits of calcium crystals other than sodium urate crystals. Articular gout is often looked at as a separate condition from visceral gout but is likely to be an earlier presentation that precedes more widespread visceral gout (as is the case in humans).
Why do these crystals become elevated? The most common reasons or associations for the development of gout or pseudogout in captive reptiles center around dietary and husbandry causes. Plant-eating reptiles, such as green iguanas, that are fed high-protein diets, especially feeding insects or canned dog/cat foods, are prone to developing this disease. For example, green iguanas fed canned pet food have uric acid levels in the blood almost double those of iguanas fed a vegetarian diet.
Dehydration due to low humidity in the cage or by having poor or unsuitable water availability (e.g., some reptiles will drink only droplets on foliage, or water is dirty) will cause a buildup of crystals because the kidneys can’t function properly. The other cause is actual kidney disease that does not allow the crystals to be removed from the body so the crystals build up in the blood. Most cases of gout and pseudogout are the result of end-stage renal failure, long-term dehydration, or being given a long-term high-protein diet.
Reptiles with visceral gout usually will be depressed and weak, and they are often thin, dehydrated, and appear sleepy and unwilling to move and eat. White to cream-colored deposits (urate tophi) can sometimes be seen in the mouth. In cases of articular gout, the joints of the legs and feet may appear swollen, and/or nodules or masses may be seen on the toes or on the ribs.
These signs of gout and pseudogout can appear slowly and can be missed by the owner until the reptile “all of a sudden” appears ill.
Any reptile species can develop gout and pseudogout.
Your veterinarian will begin with a thorough history and husbandry review, physical exam, complete blood count, plasma chemistry, and x-rays. This initial information may point towards a diagnosis of gout/pseudogout. On physical exam, finding swollen joints or dehydration may point to a diagnosis of gout/pseudogout. Your veterinarian may feel for large and misshapen kidneys that could point towards kidney disease. The bloodwork might show high levels of uric acid or indicate kidney disease. X-rays might show crystal deposits in the joints or in the tissues. X-rays may also show deposits in tissues that your veterinarian may want to biopsy and send to the lab to identify.
Often, gout will not show up on X-rays but is still the cause of the swollen joints. In this case, your veterinarian may want to get some joint fluid to look at in the clinic to see if there are urate crystals.
Once a diagnosis of gout or pseudogout is made, your veterinarian will discuss treatment options with you. In general, treatments will center on correcting dehydration, helping the kidneys regain function, reducing the high levels of uric acid in the blood (if this is elevated), reducing the amount of protein in the diet especially for plant-eating species, and using medication to reduce the pain associated with gout.
The best and most common way to correct dehydration is with fluid therapy. Depending on how severe the dehydration is, fluids may be given by soaking the reptile, giving the fluids in the mouth by a tube, or by injecting the fluids under the skin or in the veins.
If the uric acid levels in the blood are high, medications may be used in conjunction with the fluids to help reduce these levels. Allopurinol is the most common medication for this. This drug has been effective in some cases and in some reptiles to reduce the uric acid levels but in others it is not very effective; your veterinarian will discuss the options of using it in your particular case.
Photo by Dr. Kathleen Cavell
Your veterinarian will also discuss any corrections that need to be made in the diet such as reducing a high-protein diet in plant-eating species, or the proper use of supplements such as in some chameleon species that develop pseudogout when fed diets highly supplemented with vitamin D3 but low in vitamin A. Any other husbandry deficiencies, especially in lighting, humidity, soaking frequency, water quality and temperatures should be discussed and corrected.
Your veterinarian will likely suggest some pain medications as gout/ pseudogout seems to be painful and often results in the reptile not moving or eating.
In cases with visceral gout, additional treatments may be needed depending on what tissues or organs are being compromised. In cases of gout or pseudogout in the joints, toes or even limbs may need to be amputated. Reptiles usually do really well with amputated limbs.
During treatment, your veterinarian will want to monitor the reptile’s weight and blood values every few weeks.
Prognosis and Prevention
Unfortunately, the prognosis for widespread visceral gout is poor to grave even with aggressive treatments. However, the prognosis for high levels of uric acid in the blood is good if the kidneys are not too damaged and dehydration is corrected quickly, so the faster the reptile is taken to the veterinarian the better. The prognosis for articular gout/pseudogout is variable but in most cases, is a fair prognosis.
The most effective way to prevent the disease is through providing the best husbandry possible for the specific species in terms of the following:
- Appropriate water provision
- Appropriate dietary protein
- Appropriate thermal and humidity gradients
- Appropriate lighting and calcium supplementation.