Anatomic Distribution of the Carotid Bulb as Determined by Duplex Ultrasound

Ultrasound reports describe carotid plaque as being located within the bulb or bifurcation. These terms are used interchangeably; however they refer to two distinct regions. The purpose of this study was to determine the presence of a bulbous region within the common (CCA), internal (ICA) or external (ECA) carotid arteries by using ultrasound. Ultrasound images were examined from 100 carotid systems from 53 males and 47females ranging in age from 17–88 years (mean age 65 ± 15 years). An outward dilation, consistent with the expected appearance of a carotid bulb, was observed in the ICA in 49 patients. Nineteen patients had a bulb in both the ECA and ICA. In 10 patients, a bulb was present within both the ICA and CCA. In 5 patients, the CCA, ICA and ECA all contained bulbous regions. A bulb was present only within the CCA in five patients and only within the ECA in three patients. No bulb was present in nine patients. These data reveal that a bulbous region occurs in multiple segments. Defining plaque as being present within the carotid bulb is ambiguous since this applies to more than one vessel. Based on these findings, it is more appropriate to define plaque by using terms such as proximal, mid or distal. Carotid bifurcation refers to a specific anatomic region and would be acceptable as defining the location of disease. However, given carotid bulb variability, the term “carotid bulb” should be removed from common use within carotid duplex interpretations.