Ultrastructural changes in the coronary and cerebral arteries in thromboatherosclerosis have been well documented. Similar detailed studies in peripheral vascular disease (PVD) have not been described. Since PVD is frequently complicated by venous thrombosis, a comparative study of the arterial and venous pathology in patients with occlusive peripheral atherosclerosis was done. Anterior tibial artery and accompanying veins from seven cases were studied by light, transmission and scanning

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... opy. Endothelial cell morphology was abnormal in all arteries. Cells contained lipid inclusions, prominent lysosomes, and cytoplasmic filaments were disorganized. Cell junctions were altered. Endothelial cells from both the vein wall and valve were morphologically normal. Basement membrane was reduplicated in both arteries and veins. In some arteries, the basement membrane was partially obscured by the atheromatous changes. Elastic lamina in veins, valves and arteries was fragmented. Smooth muscle cells of the arterial intima has significant morphologic alterations. The cells had a disorganized pattern and contained glycogen granules, lipid droplets and lysosomes in association with lipid. The filamentous pattern was disorganized and many cells appeared devoid of a basement membrane. Pinocytic vesicles were clearly evident. Smooth muscle cells comprising vein wall and valve were unremarkable. Collagen in arteries, veins and valves was haphazardly arranged with variation in fibrillar size. In some arteries, fibrous type collagen was found. Irregular, smudged collagen was present in all vessels examined. Calcification was noted in arteries only. These findings show a) a diversity of transmural alterations in arterial wall and b) ultrastructural changes in collagen in venous wall. The former is associated with thrombotic events, the latter not.