PMC7656862_01
Multiple examples of the pathological examination of the patient. Macroscopic ischemic small intestine (a), and macroscopic ischemic sigmoid (b). Microscopic examination of subserosal artery branch with fibrinoid necrosis and nearly total obliteration of the lumen (arrow) (c), the same artery with the Verhoeff staining showing lamina elastica interna (arrow) (d). Microscopic examination of fibrinoid necrosis of another artery branch with cell dust in the artery wall, neutrophilic granulocyte infiltration, and clear narrowing of the lumen (e), and fibrin deposition (arrow) and damage of the artery wall (f). C5b-9 protein deposition in the wall of blood vessels in the submucosa and muscularis propria (arrows) (g) and subserosa (h) suggestive of an immune mediated etiology. Positive external control of C5b-9 staining in the blood vessels of a transplanted kidney with rejection (i, j).
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Based on frozen section analysis of the small intestine and sigmoid surgical specimens with macroscopic signs of extensive ischemia (Figure 1(a) and (b)), no clear evidence for a vasculitis could be found. Microscopic examination of the sectioned intestines and one adrenal gland showed however small blood vessels with thrombi in different phases varying from only fibrinoid deposits on the endothelium (existence in days) to re-endothelization (existence in weeks) (Figure 1(c)-(j)).