Ischemic injury of the human pancreas. Its basic patterns correlated with the pancreatic microvasculature.

Based on the concept of the "primary lobule" as the microcirculatory unit of human pancreas that we previously established (Yaginuma et al., submitted to Path Res Pract), ischemic injuries of this organ were microscopically screened over many autopsy cases and were classified according to the zone of the unit involved. The primary lobule was defined as a small parenchymal region, supplied by a centrally placed arteriole and drained by flanking venules, often with an islet at the center because of its close relation with arteriole. The screening disclosed twenty out of 221 autopsy cases to be harboring some ischemic injury. In a 3-D reconstruction study performed on these pancreases to correlate the injured areas with performed architecture, three types of injuries were established as comprising different categories; 1) peripheral and 2) central necroses, both presenting as multiple small foci, the distribution of which in the former exactly coinciding with the central, and that in the latter with the peripheral zone of primary lobules, and 3) peripheral atrophy, uniformly affecting the peripheral acini. The first type tended to coexist with malignant hypertension, the second type was mostly found in shock cases and the third type exclusively in those with congestive heart failure. The pathogenesis of peripheral and central necroses was explained by a working hypothesis that correlates these categories with different impediments of microcirculation, assuming that in the former, blood flow was severely impeded by constriction of relatively proximal arteries, while in the latter, sporadic occlusion at terminal arterioles was responsible for peripheral ischemia.