Sonographic evaluation of the parotid ducts: its use in tumour localization.

The previously unreported sonographic anatomy of the intraglandular parotid ducts is described, and how this aids tumour localization is illustrated. Forty patients underwent ultrasonography and computed tomography (CT) sialography for the evaluation of parotid tumours. Ultrasound identified two extra unsuspected 5 mm tumours in the superficial lobe, which could not be seen at CT. Both techniques produced similar results for deep and mixed lobe lesions. Ultrasound had one false positive mixed lesion, which surgery subsequently found to be confined to the deep lobe. The full extent of invasion in three deep lobe tumours was revealed only by CT to be parotid invasion by nasopharyngeal carcinomas. We conclude that parotid sonography with reference to the intraglandular ducts is highly accurate in localizing parotid tumours and should probably be the first-line imaging technique. Computed tomography should only be necessary for visualization of deep lobe tumour extent and in those cases where the complete tumour boundary cannot be seen by ultrasound alone.