Technical observations on the assessment of thyroid volume by palpation and ultrasonography

The diagnosis of increased thyroid volume, in field studies of goiter prevalence, has been based on inspection and palpation of the thyroid. Because clinical examination, compared with ultrasonography, has a low positive predictive value for the presence of a goiter, it overestimates goiter prevalence. It also has the problem of marked interobserver variability. This led to the use of ultrasonographic scanners in field studies. The problem with the latter is the cost and skill required for the complicated linear measures and their translation to lobe volume and then thyroid volume. We studied patients to determine whether this complicated assessment could be simplified.

We studied palpation in 31 patients with thyroid disease in whom individual ultrasonographic linear dimensions were also obtained in their 62 thyroid lobes to determine their relationship to thyroid lobe volume.

Palpation revealed poor discrimination of smaller thyroid sizes as determined by ultrasonography. Stepwise linear regression (backward selection) revealed that of the 3 thyroid dimensions, only the lateromedial dimension of the thyroid lobe had a significant correlation to lobe volume, accounting for 82.5% of the variability in lobe volume. The lobe volume (in milliliters) is given by the lobe lateromedial dimension (in centimeters) multiplied by 13 minus a constant of 15.

A simple linear ultrasonographic measurement of the thyroid lateromedial dimension, which can be done with little training, is as good as more complicated measures of thyroid volume estimation by ultrasonography and is an ideal method for identifying goiters in field surveys.