PERCUTANEOUS ULTRASONOGRAPHICALLY GUIDED RADIOFREQUENCY HEAT ABLATION FOR TREATMENT OF HYPERTHYROIDISM IN CATS.
K Mallery, R Pollard, W Homof, E Feldman,

J Am Vet Med Assoc 2003;223:1602–1607

The purpose of this study was to evaluate the efficacy of radiofrequency heat ablation for treatment of cats with naturally occurring hyperthyroidism.

Nine hyperthyroid cats were included in the study. A solitary thyroid mass was identified via pertechnetate scintigraphy and cervical ultrasound in 4 cats (LTNI). Two thyroid nodules were found in each of the other 5 cats (131). Each cat was anesthetized and positioned in dorsal recumbency. With ultrasound guidance, an insulated 20-gauge catheter stylet was inserted into the thyroid mass and radiofrequency pulses were applied, leading to heat-induced coagulation necrosis of the tissue. In BI cats, the larger mass was ablated.

Heat ablation was performed once on each of 3 thyroid nodules and twice on I nodule in the 4 UNI cats. Three of the 4 cats were euthyroid after the procedure, and hyperthyroidism recurred in all 3 cats: 4, 7 & 19 months post-treatment (Rx), respectively. One of these 3 cats had a second ablation performed and remained euthyroid for an additional 9 months. The fourth cat had reduction in sTT4 but did not become euthyroid. In the BI cats, heat ablation was performed once in 2 cats, and each became euthyroid, for 7 & 9 months, respectively. Heat ablation was performed twice in 2 cats, and neither cat was euthyroid after the first procedure. One was euthyroid for 2 months after the second procedure, and I is euthyroid at the time this abstract was written (9 months post-Rx). The fifth cat had 3 procedures performed and was euthyroid after the second and third procedures, for 5 months each time. Homer's syndrome developed in 2/9 cats, and resolved within 2 months in both cats.

Unipolar radiofrequency heat ablation is feasible and effective as a short-term treatment for feline hyper-thyroidism, but has not been effective as a permanent treatment.