The Thoracic Duct

Abstract

In a search for atheromata, multiple sections of thoracic ducts from 119 autopsied individuals, varying in age from newborns to 91 years, were studied histologically with various stains, including fat stains on frozen sections of 84 different ducts. No atheromata were found. Changes in the wall of the duct apparently related to aging included increasing density, minimal intimal fibrosis, degenerative changes in the internal elastic plate, and the appearance of occasional microscopic fibrous polypoid projections into the lumen. Although fat was demonstrated with ease in the wall of the duct and did not appear to be related to the intimal fibrosis, it appeared to be passing through the wall of the vessel without exciting either inflammatory reaction or fibrosis. The findings in the thoracic duct were evaluated with respect to the conventionally accepted definitions of atherosclerosis and phlebosclerosis. It was concluded that the sclerotic changes found in the thoracic duct are more like phlebosclerosis and unlike atherosclerosis in that they bear no relationship to lipid infiltration and reaction thereto. The term "lymphatic sclerosis" was suggested for the condition. The common presence of lipid in the wall of the thoracic duct without reaction and without true atheroma formation indicates that factors beyond mere lipid infiltration of vascular walls must play an important role in the pathogenesis of atherosclerosis.