Pilot study of the potential of 3D ultrasound to measure tonsillar volume and hypertrophy

Obstructive sleep apnea (OSA), results in approximately 4-5 million outpatient visits per year in the United States. In pediatric patients, OSA is primarily caused by adenotonsillar hypertrophy, and therefore, adenotonsillectomy remains an effective surgical treatment. We investigate whether 3D ultrasound (3DUS) imaging can accurately and objectively assess tonsillar hypertrophy for the potential identification and stratification of candidates for adenotonsillectomy.

A prospective study was performed evaluating pediatric patients (N = 17) between the ages of 4-14 years who were undergoing adenotonsillectomy for OSA symptoms. On the day of surgery, tonsillar ultrasound was performed by a single attending radiologist. Tonsillectomy was performed and each tonsils' principal axes and physical volume by water submergence were measured. The findings were compared using paired T-test, Pearson correlation coefficient and Bland-Altman analysis.

The average tonsillar physical measurements of length, width and height were 1.54 ± 0.28, 2.0 ± 0.31 cm and 2.72 ± 0.41 cm, and 1.73 ± 0.17, 1.61 ± 0.21 mm and 2.98 ± 0.28 mm from physical and 3DUS estimations, respectively (P < 0.001 for all measurements). The average tonsillar volume was 3.84 ± 1.23 ml and 4.30 ± 1.15 ml from physical and 3DUS measurements, respectively (p = 0.04). The Bland-Altman mean difference ± 95% limit of agreement between length, width, height, and volume results from the two measurements were -0.186 ± 2.01 cm, -0.393 ± 6.33 cm, 0.25 ± 7.71 cm, and 0.45 ± 2.32 ml, respectively.

While 3DUS is feasible, it may not be an accurate estimate of tonsillar volume for assessing hypertrophy. A larger study will be required to establish the accuracy of 3DUS measurements of tonsillar volume.