Snake Gout

Biopsy of this swelling revealed renal gout © RVC

Introduction

Gout is a metabolic disease where there is a precipitation of urate crystals in tissue. There are two types of gout in animals.

• In primary gout there is an overproduction of uric acid related to an innate metabolic problem.
• In secondary gout, acquired disease interferes with the uric acid metabolism. Terrestrial reptiles are predisposed to secondary gout since nitrogenous waste is excreted as uric acid.

In snakes, kidney disease often leads to the development of a visceral gout where uric acid crystals (tophi) are deposited in subcutaneous and internal tissues.

For more information on excretion, see Lizard and Snake Excretion.

Examination

History may show poor husbandry including limited access to water. Snakes often present as anorexic and lethargic. Often if kidney disease is involved there is a palpable lump in the caudal third.

For a differential diagnosis list of other causes of lumps in the body, see Snake Lumps and Bumps.

Tophi in renal tissue - © RVC

Diagnosis

The diagnosis of gout may be suspected on history and physical examination. Biochemistry may indicate a hyperuricaemia. Sometimes radiography is useful if calcium is deposited with the urate crystals. Biopsy of any lumps may be useful. A definite diagnosis is the demonstration of tophi in diseased tissue.

For more information on physical examinations, see Snake Physical Examination.

For more information on biopsy collection, see Specimen Collection and Evaluation.

Tophi in diseased tissue © RVC

Therapy

Supportive treatment especially aimed at rehydration may be useful but gout carries a poor prognosis. Previously allopurinol (a xanthine oxidase inhibitor that decreases formation of uric acid) has been recommended as a treatment of hyperuricaemia in reptiles and birds but in fact appears to be of little use. Other drugs such as uricases (enzymes involved in the degradation of uric acid to allantoin) may be more useful.

For more information, see Snake Supportive Care.

Prevention

Any bouts of dehydration will predispose to the development of gout so good husbandry is important in prevention. Vets should ensure adequate hydration of reptiles prior to any drug therapy but especially when using nephrotoxic drugs.

For more information on good husbandry practices, see Snake Husbandry.