Introduction:  
Ethanol ablation (EA) for symptomatic thyroid cysts has produced highly variable and often disappointing results, probably because of differences in technical approach. Since January 2015 we employ a new, highly standardized, modified, ultrasound (US)-guided EA technique.

Aim: 
To evaluate the one-year efficacy of a modified EA technique.

Patients and Methods:
EA was performed in an outpatient setting, under US guidance, after local anesthesia, and by a trans-isthmic approach. After aspiration of cyst fluid, residual debris was removed by NaCl 0.9% irrigation, followed by instillation of ethanol 96%, of about 50% of the original cyst fluid volume. After a retention time of 2 minutes, all ethanol was removed under US guidance, thereby ensuring that removal was complete, and that the cyst had collapsed completely. Then, all patients were instructed to apply local finger pressure over the treated cyst for 20 minutes. Outpatient visits were scheduled one week, 3, 6 and 12 months after EA. Only patients with a 12-month follow-up were included for analysis. Successful treatment was defined as a cyst volume reduction of at least 75%, failure was defined as a reduction < 50%.

Results:
So far, 42 patients have completed the one-year follow-up. Baseline cyst volumes ranged from 2.3 – 200 ml, with a median of 18 ml. Successful treatment was observed in 30/42 (71%) of patients, two patients had a partial response (50%-75%) and treatment failure occurred in ten patients (24%). Median cyst volumes of successfully treated patients at baseline, 3, 6, and 12 months were 18.0, 2.0, 0.9 and 0.6 ml, respectively, i.e. equivalent to a mean reduction of 92 ± 1.9% at 12 months (P < 0.001). Transient pain, and mild thyroiditis were the main complications, and occurred in a small number of patients

Conclusion:
Modified EA produced a lasting volume reduction of at least 75 % in nearly three quarters of patients, and was not associated with substantial side effects. It is recommended as a first line treatment, before considering surgery.