The current study showed that intraoperative blood loss and RBC transfusion in aneurysmorrhaphy were significantly less in endotension cases than type II endokleak cases.
In the past, open graft replacement was the main treatment for aortic aneurysm. However, since the devices for EVAR was approved in Japan in 2006, EVAR has been generally accepted as the optional treatment for repairing abdominal aortic aneurysms, especially in elderly patients because of its low invasiveness and rapid postoperative recovery. Endoleak is a major complication of EVAR, and management of endoleaks has been a major issue for more than 20 years. Type II endoleak has leakage through retrograde collateral blood flow such as lumbar, inferior mesenteric or internal iliac arteries. Type II endoleaks are generally benign and have little adverse effect on the outcome of EVAR. However, Van Marrewijk  found that type II endoleak were significantly associated with dilatation of the aneurysm sac over time and it was widely recognized that such patients should be treated with endovascular therapy or conversion to open repair.
The incidence of endotension after EVAR is 1.5-5% [13, 14]. Endotension causes enlargement of the vessel and aneurysm diameter in spite of no apparent endoleak. The mechanism of endotension is not clear. It has been hypothesized that if the leak is small, the small hole in the stent graft may be blocked with a thrombus, resulting in an undetectable leak on imaging studies . Some investigators have suggested that endotension results from direct pressure transfer from the adjacent aortic lumen to the aneurysm . Another hypothesis was that leakage fluid accumulates progressively in the aneurysm sac due to increased permeability of covering material of the stent graft. This increased permeability has been reported primarily with polytetrafluoroethylene stent grafts and inhibits thrombus formation in the aneurysm sac . In endotension, fibrinolysis in the aneurysm sac was also observed . This hyperfibrinolysis may be a risk for bleeding.
The largest published series was from European Collaborators on Stent/graft Techniques for aortic Aneurysm Repair (EUROSTAR) registry (3595 patients), with a 9 % of type II endoleak cases diagnosed during follow-up . It was also reported that 2.4 ~ 6 % of patients were required secondary treatment due to endotension after EVAR [5, 19]. CT (computed tomography), MRI (magnetic resonance imaging), and US (ultrasound) are commonly used to diagnose endoleak types, although guidelines recommend CTA (computed tomography angiography) after 6 months . In this study, preoperative endoleak type was diagnosed by CT, CTA, and angiography performed every 1 ~ 12 months after EVAR. It has been suggested that four-dimensional flow-sensitive MRI after EVAR was useful for identifying the type of endoleak and predicting dilatation of the aneurysm one year later , however there were limitations in the number of facilities available for testing and the inability to test with stainless stent-grafts. Contrast-enhanced ultrasound may be highly accurate in detecting and classifying endoleaks.
Treatment options for type II endoleaks include transarterial chemoembolization, coil embolization, translumbar embolization, laparoscopic surgery, open graft replacement, and aneurysmorrhaphy . While transarterial chemoembolization and coil embolization are the most common treatments, often require repeated intervention. In particular, 51 % of patients treated with only coil embolization required secondary intervention . Patients receiving these secondary interventions were reported to have a higher probability of subsequent additional embolization . Recently translumbar embolization using liquid embolization agents (Onyx, glue, thrombin, polymers) is popular, however these agents are expensive and unintentional leakage has been reported to cause various complications . Laparoscopic branch ligation is less invasive than open surgery, however this procedure is technically difficult and may eventually convert to open surgery if the periaortic area is inflamed . Open graft replacement is a standard surgical treatment, however it is highly invasive because of large incision, aortic cross clamp and, graft explantation and is associated with significant mortality (often ~ 20 %) [8, 24, 25]. Aneurysmorrhaphy, a minimally invasive open surgical repair against aneurysm expansion, is recently reported in some case reports [10, 11]. This procedure is a modified technique that is not require aortic cross clamp, graft explantation, and systemic heparinization. In our institution, aneurysmorrhaphy is standard surgical treatment in patients of aneurysm enlargement after EVAR.
In type II endoleaks, the number of vessels entering the aneurysm varies. Previous studies have reported that risk factors for persistent type II endoleaks are large, patent inferior mesenteric artery, and more than two lumbar arteries on preoperative CTA . Therefore, it has been shown to be reasonable to evaluate the inflow vessels preoperatively. In our institution, aneurysmorrhaphy often caused massive bleeding in the cases of type II endoleak, but not in cases of endotension. The present study demonstrated that intraoperative blood loss is much less in endotension comparing to type II endoleak. Furthermore, intraoperative blood loss in our 18 cases have some tendency to increase in type IIb endoleak (two or more inflow vessels) than type IIa endoleak (one inflow vessel), indicating that the greater the number of inflow vessels, the greater the intraoperative blood loss. Preoperative precise prediction of blood loss helps anesthesiologists to plan an optimum strategy of intraoperative cardiohemodynamic management and leads to reduce unnecessary preoperative blood orders.
We recognize several limitations to this study. Firstly, the blood transfusion trigger was not defined because anesthesiologists were not unified in these 18 cases. Secondly, the total number of aneurysmorrhaphy was small, and this study design was a retrospective and observational.