Percutaneous intrathyroidal ethanol injection

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Ultrasound guided percutaneous ethanol injections are a rare method of treating feline hyperthyroidism.

This method has been used successfully in humans suffering from hyperthyroidism as well as hyperparathyroidism and in dogs with hyperparathyroidism[1] Ethanol injections result in vascular thrombosis and coagulative necrosis within the treated parenchyma [2].

Ultrasound-guided percutaneous ethanol treatment of eight hyperthyroid cats determined to have unilateral disease by T4 and free T4 hormone measurement, cervical ultrasound and nuclear scintigraphic scan has been reported[3]. The affected thyroid lobe was visualized ultrasonographically and injected percutaneously via ultrasound-guided needle placement. Any cystic fluid present within the thyroid lobe was aspirated before treatment. A 100% ethanol solution was injected, with the volume injected determined through ultrasound estimation of complete infiltration of ethanol within the thyroid lobe. All cats treated had normal T4 concentrations within 48 hrs of treatment and remained euthyroid for at least 18 months after treatment. Two of the cats had a change in voice, possibly because of unilateral laryngeal paralysis secondary to ethanol extravasation into cervical tissues and damage to the recurrent laryngeal nerve[4].

Although treatment of unilateral disease appears effective, use of anti-thyroidal drugs, surgery or radioiodine may be better in the long term. In addition, ultrasound-guided percutaneous ethanol injection requires great expertise and is not readily available.

Treatment of hyperthyroid cats with confirmed bilateral disease has been less successful. Transient euthyroidism was observed in all cats, but no patients remained euthyroid for longer than 6 months. Complications included ipsilateral and transient Horner's syndrome, dysphonia and laryngeal paralysis.

References

  1. Bennedbaek, FN Karstrup, S & Hegedus, L (1997) Percutaneous ethanol injection in the treatment of thyroid and parathyroid diseases. Eur J Endocrinol 136:240-250
  2. August, JR (2006) Consultations in feline internal medicine. Vol 5. Elsevier Saunders, USA. pp:203-204
  3. Goldstein, RE et al (2001) Percutaneous ethanol injection for treatment of unilateral hyperplastic thyroid nodules in cats. J Am Vet Med Assoc 218:1298-1302
  4. Wells, AL et al (2001) Use of percutaneous ethanol injection for treatment of bilateral hyperplastic thyroid nodules in cats. J Am Vet Med Assoc 218':1293-1297