Human acute pancreatitis: a light and electron microscopic study.

The histology and ultrastructure of resected pancreas from seven patients suffering from acute haemorrhagic pancreatitis were studied. Special attention was paid to necrotic acini and zymogen granules. Acinar cells in the border of necrotic and non-necrotic parenchyma contained lipid droplets, autophagic vacuoles, bundles of intermediate filaments and degenerated cell organelles, including zymogen granules, PAS-positive material derived from secretory proteins was situated in dilated acinar lumina and in the interstitium, and proved to be fibrillar in fine structure. There were thrombosed vessels and extravasated erythrocytes at the border of the parenchymal necrosis. Bundles of intermediate filaments were often the only identifiable structures in the severely necrotic acinar cells. The amount of lipid was decreased in damaged fat cells. Older fat necroses were surrounded by myofibroblasts. It was concluded that acinar and fat cells undergo concomitant necrosis in the inflamed pancreas, zymogen granules degenerate in the acinar cells at the border of necrotic and non-necrotic areas, and secretory proteins may be displaced in the interstitium outside acinar lumina. Myofibroblasts participate in the healing of autodigestive injuries.