Anatomical variation and quantitative histology of the normal and enlarged carotid body.

The carotid bodies from 150 consecutive cases coming to necropsy were examined to determine the degree of anatomical variation of the organ. Single, double and bilobed variants were found. The origin of the carotid body was variable, the angle of the carotid bifurcation being the most typical, but a minority were encountered on the internal or external carotid arteries, the common carotid artery and the ascending pharyngeal artery. Carotid bodies which were enlarged had no preferred site or origin, but some showed early or pronounced nodularity. Both carotid bodies from 100 of these cases were subjected to detailed qualitative and quantitative histological study. From these measurements we were able to define hyperplasia of the organ as a differential sustentacular cell count in excess of 47 per cent., a lobular diameter over 565 micrometers, and a combined carotid body weight over 30 mg. Carotid body hyperplasia occurred in cases of myocardial hypertrophy secondary to both hypoxaemia and systemic hypertension.