In Vivo Accuracy of Ultrasound for Sizing Salivary Ductal Calculi

Objectives The present study was developed to evaluate the accuracy of in vivo ultrasound sizing for parotid and submandibular salivary gland calculi, as compared with ex vivo pathology sizing with a standard plastic ruler after extraction. Study Design Retrospective chart review. Setting Ultrasound is frequently used to size salivary calculi and make treatment decisions, but the accuracy of measurements from this modality has not been validated. Subjects and Methods We evaluated and reviewed the charts and ultrasound examinations of 167 patients who underwent procedures for the treatment of sialolithiasis involving the parotid and submandibular glands. US examinations were performed between 2009 and 2016 in a tertiary-level hospital setting by the senior author. Measurements were collected from ultrasound evaluation before sialolithotomy, and pathology measurements were taken after removal. Ultrasound measurements in millimeters were compared with the measurements collected with a ruler. The differences were calculated and compared. Results A total of 167 calculi measurements were compared. Good concurrent validity between pathology and ultrasound measurements was suggested by a Pearson correlation of 0.92 (95% CI, 0.887-0.937). On Bland-Altman plot, correlation of the difference between US and pathology measurements showed a mean difference of 0.095 mm (95% CI, –0.19 to 0.38 mm) with a limit of agreement ranging from –3.59 mm (95% CI, –3.84 to –3.34 mm) to +3.78 mm (95% CI, +3.53 to +4.03 mm). Conclusions Ultrasound is an accurate, relatively precise, and minimally invasive imaging tool for salivary gland sialolithiasis. Preoperative size of calculi can be used to guide management and clinical decision making. Level of Evidence 2C.