Aneurysm sac hygroma: A cause of endotension

Purpose: To describe a new pathophysiological mechanism for endotension. Case Reports: Four patients developed aneurysm sac expansion after repair o f abdominal aortic aneurysms, one with a conventional polytetrafluoroethyle ne (PTFE) graft and the others with a variety of commercially made endograf ts (2 PTFE, I Dacron). Pressures within the sacs were nonpulsatile and appr oximately half the systemic blood pressure. Attenuation on computed tomogra phy (CT) was significantly less in the sac than in the graft in 3 of the pa tients. A clear, highly viscous fluid was aspirated from all 4 sacs, suppor ting the diagnosis of aneurysm sac hygroma. Prominent local hyperfibrinolys is in the sac was combined with signs of local coagulation activation. Conclusions: A new mechanism for continued sac expansion based on aneurysm sac hygroma is proposed. Measurement of attenuation may be of diagnostic va lue. It is further proposed that local hyperfibrinolysis/coagulation may pr omote rebleeding, liquefaction, and continued expansion analogous to the ch ronic subdural hematoma.