Segmental mediolytic arteritis involving hepatic arteries.

Segmental mediolytic arteritis is a rare, noninflammatory arteriopathy that involves the splanchnic arteries of adults with shock and the coronary arteries of neonates with hypoxemia. We report the first case (to our knowledge) of segmental mediolytic arteritis involving the hepatic arteries. The lesion begins with cytoplasmic vacuolar degeneration of the arterial smooth-muscle cells, which then progresses to coalescence of vacuoles, leading to disruption of the media, intramural hemorrhage, and periadventitial fibrin deposition. Segmental mediolysis results in arterial wall defects, which can lead to dissecting aneurysms or hemorrhage due to arterial rupture. The intima and internal elastica are spared from the lytic process, and there is minimal periadventitial inflammation. Segmental mediolytic arteritis is not a true arteritis; therefore, segmental mediolytic arteriopathy may be a preferable term. Morphological similarities exist between segmental mediolytic arteritis and arterial fibromuscular dysplasia. In our case, hepatic ischemia correlated with mediolysis involving the hepatic arterial branches. Segmental mediolytic arteritis is thought to be due to an inappropriate vasospastic response, developing in the setting of hypoperfusion and hypoxemia.