Percutaneous ultrasound-guided radiofrequency heat ablation for treatment of hyperthyroidism in cats

Kevin F. Mallery Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616.
Present address is California Veterinary Specialists, 100 N Rancho Santa Fe Rd, Ste 133, San Marcos, CA 92069.

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Rachel E. Pollard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Richard W. Nelson Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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William J. Hornof Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Edward C. Feldman Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Abstract

Objective—To determine efficacy and safety of percutaneous radiofrequency heat ablation for treatment of hyperthyroidism in cats.

Design—Prospective study.

Animals—9 cats.

Procedure—Hyperthyroidism was diagnosed via clinical signs and high serum total (TT4) and free thyroxine (fT4) concentrations. One or 2 hyperfunctional cervical thyroid nodules were detected by use of scintigraphy and ultrasonography. If cats had 1 abnormal thyroid lobe, heat ablation was performed on that lobe; if cats had 2 abnormal lobes, heat ablation was applied to the larger lobe. Overall, heat ablation was performed 14 times in the 9 cats. Clinical signs and serum TT4, fT4, and calcium concentrations were monitored daily for 2 days after the procedure, weekly for the first month, and then monthly. Laryngeal function was evaluated and cervical ultrasonography and thyroid scintigraphy were also performed. Monitoring continued for as long as 9 months after heat ablation if a cat became euthyroid or until an owner chose an alternative treatment because of recurrence of hyperthyroidism.

Results—Serum TT4 and fT4 concentrations transiently decreased after all 14 heat ablation procedures (≤ reference range after 10 of 14 treatments) within 2 days after the procedure. Cats were euthyroid for 0 to 18 months (mean, 4 months). Hyperthyroidism recurred in all cats. Adverse effects included transient Horner's syndrome (2 cats) and laryngeal paralysis without clinical signs (1 cat).

Conclusions and Clinical Relevance—Percutaneous heat ablation as a treatment for hyperthyroidism in cats is effective transiently but not permanently. (J Am Vet Med Assoc 2003;223:1602–1607)

Abstract

Objective—To determine efficacy and safety of percutaneous radiofrequency heat ablation for treatment of hyperthyroidism in cats.

Design—Prospective study.

Animals—9 cats.

Procedure—Hyperthyroidism was diagnosed via clinical signs and high serum total (TT4) and free thyroxine (fT4) concentrations. One or 2 hyperfunctional cervical thyroid nodules were detected by use of scintigraphy and ultrasonography. If cats had 1 abnormal thyroid lobe, heat ablation was performed on that lobe; if cats had 2 abnormal lobes, heat ablation was applied to the larger lobe. Overall, heat ablation was performed 14 times in the 9 cats. Clinical signs and serum TT4, fT4, and calcium concentrations were monitored daily for 2 days after the procedure, weekly for the first month, and then monthly. Laryngeal function was evaluated and cervical ultrasonography and thyroid scintigraphy were also performed. Monitoring continued for as long as 9 months after heat ablation if a cat became euthyroid or until an owner chose an alternative treatment because of recurrence of hyperthyroidism.

Results—Serum TT4 and fT4 concentrations transiently decreased after all 14 heat ablation procedures (≤ reference range after 10 of 14 treatments) within 2 days after the procedure. Cats were euthyroid for 0 to 18 months (mean, 4 months). Hyperthyroidism recurred in all cats. Adverse effects included transient Horner's syndrome (2 cats) and laryngeal paralysis without clinical signs (1 cat).

Conclusions and Clinical Relevance—Percutaneous heat ablation as a treatment for hyperthyroidism in cats is effective transiently but not permanently. (J Am Vet Med Assoc 2003;223:1602–1607)

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