Segmental arterial mediolysis developing during treatment for severe acute pancreatitis.

We describe a case of segmental arterial mediolysis that developed during treatment for severe acute pancreatitis. The patient is a 41-year-old male who was hospitalized for severe alcoholic pancreatitis. The clinical course of acute pancreatitis was favorable. On the 10th hospital day, the patient experienced hemorrhagic shock. Contrast-enhanced computed tomography revealed newly developed aneurysms distant from the site of pancreatic inflammation, leading to a diagnosis of segmental arterial mediolysis. The aneurysm suspected of rupture was successfully embolized by catheter intervention, and the subsequent clinical course was favorable.The unruptured aneurysm resolved spontaneously under conservative management. On day 142 after onset, the patient developed headache and vomiting, and imaging revealed an intraventricular hematoma, which was suspected to be associated with segmental arterial mediolysis. To our knowledge, this is the first report describing the relationship between segmental arterial mediolysis and acute pancreatitis. This case underscores the importance of considering segmental arterial mediolysis as a potential cause of intra-abdominal hemorrhage in patients with pancreatitis. Notably, aneurysm formation and rupture occurred within a very short period; no aneurysm was detected on day 3, whereas rupture occurred on day 10. This suggests that aneurysm development in segmental arterial mediolysis may occur within 7 days. Our observation provides valuable clinical insight into the rapid progression of aneurysms in segmental arterial mediolysis and highlights the need for early recognition and prompt management in similar clinical settings.