Evanescent Hyperechoic Changes After Fine‐Needle Aspiration Biopsy of the Thyroid in a Series With a Low Overall Prevalence of Complications

Objectives The purpose of this study was to assess the frequency of and risk factors for fine‐needle aspiration biopsy (FNAB)‐related complications in Japanese patients with thyroid nodules evaluated by standard FNAB techniques. Methods Six hundred fifty‐three consecutive Japanese patients with 742 nodules who had undergone FNAB were enrolled. Nodule characteristics were evaluated, and thyroid volumes were measured. Fine‐needle aspiration biopsy–related complications were identified on the basis of sonographic findings and patients’ conditions after undergoing FNAB. Comparisons of patients’ backgrounds and nodule characteristics were made between those with and without complications. Results The prevalence rates for FNAB‐related complications, including acute transient thyroid swelling after FNAB and appearance of anechoic lesions, were 0.13% and 0.94%. In this study, we could not identify risk factors for FNAB‐related complications. The sudden appearance of bright hyperechoic foci within the thyroid immediately after biopsy was reported as an FNAB‐related unfamiliar appearance in 5 cases. Experimental FNA using resected porcine thyroid tissue suggested that the etiology of the hyperechoic appearance may be artificial air bubbles or reversed flow of aspirated fluid. Conclusions Fine‐needle aspiration biopsy–related complications are rare if preventive measures are performed and are not specific to Japanese patients with thyroid nodules. The sudden appearance of bright hyperechoic foci may be cause by contamination from air or fluid.