ISSN 2398-2985      

Gout

Jreptile
Contributor(s):

Mark Naguib

Yvette Rowntree


Introduction

  • Cause: inflammation due to deposition of uric acid crystals in intra-articular, peri-articular and visceral tissues, secondary to hyperuricemia. The hyperuricemia can be due to a number of etiologies, most commonly renal disease.
  • Signs: lameness, joint swellings, pale deposits within oral mucosa, neurological signs, lethargy, anorexia.
  • Diagnosis: persistently elevated blood uric acid levels, demonstration of crystals and tophi in joints or tissues.
  • Treatment: pharmacological reduction of blood uric acid levels, analgesia, husbandry changes, euthanasia if refractory.
  • Prognosis: potentially very guarded, depending on underlying etiology, however some animals may do well long-term with palliative care.

Pathogenesis

Etiology

  • Although primary gout is seen in humans and in some dog breeds, in reptiles it is generally secondary.
  • Hyperuricemia occurs secondary to renal disease, chronic dehydration or excessive or inappropriate protein intake .
  • Uric acid crystals (monosodium urate) crystals are deposited on articular, periarticular and visceral surfaces eliciting a marked inflammatory response.

Predisposing factors

General

  • High protein diet, particularly excessive purine intake.
  • Chronic dehydration.
  • Renal disease Renal disease.
  • Inappropriate administration of potentially nephrotoxic drugs, eg gentamicin Gentamicin.

Pathophysiology

  • Uric acid is the primary waste product of protein metabolism in terrestrial reptiles.
  • Purines are broken down to xanthine which is converted to uric acid through the action of xanthine oxidase. Uric acid is then excreted through the renal tubules.
  • Increased uric acid production, eg due to a diet high in animal protein in a herbivorous species, or decreased excretion, eg renal disease, chronic dehydration, leads to hyperuricemia.
  • Prolonged hyperuricemia leads to the precipitation of insoluble urate crystals in the form of monosodium urate in articular, periarticular and visceral tissues. Accumulated microscopic crystals coalesce to form grossly visible tophi.
  • The presence of crystals and tophi elicits a marked inflammatory response which is painful.

Timecourse

  • Chronic over weeks, months and years, however clinical signs are often only noticed and animals presented late in the course of disease.

Epidemiology

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Reavill D R & Schmidt R E (2010) Urinary tract diseases of reptiles. J Exotic Pet Med 19 (4), 280-289 VetMedResource.
  • Zwart P (2006) Renal pathology in reptiles. Vet Clin North Am Exotic Anim Pract 9 (1), 129-159 VetMedResource.
  • Hernandez-Divers S J (2004) Endoscopic renal evaluation and biopsy of chelonia. Vet Rec 154 (3), 73-80 PubMed.

Other sources of information

  • Klaphake E, Gibbons P M, Sladky K K & Carpenter J W (2018) Reptiles. In: Exotic Animal Formulary. Ed: Carpenter J. Elsevier Saunders, USA. pp 81-166.
  • Duncan M (2015) Gout in Exotic Animals. In: Fowler’s Zoo and Wild Animal Medicine. Eds: Miller R E & Fowler M E. Elsevier Saunders, USA. pp 667-670.
  • Mader D R (2006) Gout. In: Reptile Medicine and Surgery. Elsevier Saunders, USA. pp 793-800.
  • Johnson J D (2004) Urogenital System. In: BSAVA Manual of Reptiles. Eds: Girling S J & Raiti P. BSAVA, UK. pp 261-272.

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