Ultrasonography of Incidental Thyroid Nodules: A Systematic Review and Meta-analysis of Prevalence

An increasing number of physicians use ultrasound (US) to evaluate the thyroid. Consequently, many individuals in the general population have been diagnosed with thyroid nodules. However, there has been no systematic review examining the prevalence of incidental thyroid nodules among asymptomatic adults or elucidating the associated factors.

We searched the MEDLINE and Embase databases to identify studies focused on thyroid incidentaloma observed through the US.

A total of 95,394 adults were enrolled, and 35,971 people were found to have thyroid incidentaloma through the US. The results revealed that the prevalence of incidentaloma was 30.6% (95% confidence interval: 26.3-36.3, I ² = 99%, P < 0.01). The subgroup analysis indicated that the prevalence rates of thyroid incidentaloma were 34% and 23% for females and males, respectively. The prevalence of thyroid incidentaloma was 42% and 20% for individuals aged more than 50-55 and <50-55 years, respectively. The prevalence of thyroid incidentaloma was 60% and 25% for high-frequency (>12 MHz) and low-frequency US, respectively. The majority of thyroid incidentalomas were smaller than one centimeter and had singular nodules.

According to this systematic review and meta-analysis, up to 30% of asymptomatic adults will have thyroid incidentalomas detected by the US. More thyroid incidentalomas were found in women, older people, and those with a higher-frequency US.