Vitamin D toxicosis

From Dog
Cholecalciferol rodenticide poisoning in a dog showing serosal calcification[1]

Vitamin D intoxication is a well described disease of dogs, commonly reported due to ingestion of rodenticides containing cholecalciferol (vitamin D3).

This toxicosis can also arise as a consequence of a variety of formulations and brand names as well as chronic dietary or iatrogenic oversupplementation with vitamin D during treatment of primary hypoparathyroidism[2].

The major pathophysiologic effect is hypercalcemia, which can cause acute kidney injury as a result of altered cell membrane permeability, altered calcium pump activity, decreased cellular energy production, and cellular necrosis[3].

The toxic dose in naturally exposed dogs is 1.5 to 8 mg/kg[4][5].

Within 12 - 24 hours after ingestion, dogs exhibit vomiting, depression, anorexia, polyuria and diarrhea[6].

A tentative diagnosis can be made on history of exposure, presenting clinical signs, but no definitive tests are available to date to confirm toxicosis caused by these compounds. However, blood tests often show characteristic hypercalcemia, hyperphosphatemia and elevated blood urea nitrogen and serum creatinine.

Other tests may assist diagnosis such as demonstration of increased levels of serum 25-monohydroxy vitamin D3 concentration and reduced serum intact parathormone concentration[7].

Affected dogs can die from calcification of cardiac tissue weeks after ingestion[8].

A differential diagnosis would include other toxin ingestions and other causes of hypercalcemia such as lymphosarcoma, hypoadrenocorticism, chronic renal disease and primary hyperparathyroidism.

The hypercalcemia can be managed clinically with pamidronate, combined with intravenous fluids or intermittent hemodialysis.

Long term prognosis is guarded.

References

  1. Merck Veterinary Manual
  2. Drazner FH (1981) Hypercalcemia in the dog and cat. J Am Vet Med Assoc 178:1252–1256
  3. Morrow CM (2001) Cholecalciferol poisoning. Vet Med pp:905-911
  4. Murphy MJ (2002) Rodenticides. Vet Clin North Am Small Anim Pract 32(2):469-484
  5. Rumbeiha WK et al (2000) Use of pamidronate di­sodium to reduce cholecalciferol-induced toxicosis in dogs. Am J Vet Res 61(1):2-3
  6. Welch SL (2002) Oral toxicity of topical preparations. Vet Clin North Am Small Anim Pract 32(2):443-453
  7. Dorman DC & Beasley VR (1989) Diagnosis and therapy for cholecalciferol toxicosis. In: Current veterinary therapy X: small animal practice, ed. Kirk RW, pp:148–152. WB Saunders, Philadelphia, PA
  8. Fan TM et al (1998) Calcipotriol toxicity in a dog. J Small Anim Pract 39(12):581-586