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2 15 1 Cases Number of cases Fig Aneurysm diameter at first presentation (mm) Number of cases by initial abdominal aortic aneurysm (AAA) diameter. Among all AAA patients, 125 patients (48.1%) were underwent early elective operation (early surgery group; ) and 135 patients (51.9%) were not offered operative treatment (observation group; ). Almost all patients of early surgery group had 5 cm AAA, and the other side almost all patients with 5 cm AAA were not offered operation. 5cm 4cm 5cm 5cm t ANOVA Tukey Kaplan-MeierLog rank AAA cm cm p < Fig. 1 5cm 74 6cm 86 5cm cm92 5cm43 3 4cm cm cm 5cm

3 Cases 40 Death of other disease 30 Death of rupture suspected 20 Alive without elective surgery Death of rupture without operation Death of rupture with operation Alive through rupture with operation 10 Death of other disease 0 Fig. 2 <50mm 50mm 4cm observation 5cm observation Alive without elective surgery Prognosis of non-operated patients. Abdominal aortic aneurysm (AAA) rupture was occurred in 14 cases in the non-operated patients. The all ruptured AAA reached 5 cm, and no rupture had occurred to the aneurysms smaller than 5 cm in diameter. Table 1 Characteristics of the 4 patients suffered rupture in 4-cm observation group Age Diameter Interval (mo) Diameter at first 1st presentation- Final presentationat rupture (cm) presentation (cm) rupture rupture refused operation refused operation presented only one time refused operation 4cm55 5cm 43 5cm 12 5cm28 4 Fig. 2 4cm cm cm 5cm Table 1 5cm cm

4 Fig Time after first presentation (mo) Cumulative incidence of probable rupture. The cumulative incidence of probable rupture was significantly higher in 5 cm-observation group ( ) than in 4 cm-observaton group ( ) (p<0.0001). 14 Fig. 3 4cm cm p < p = cm 5cm Fig. 4 5cm 5 4cm cm p < cm cm 5cm 5cm2 5 5cm cm 67.3 p = Fig Time after first presentation (mo) Survival curves after first presentation, using Kaplan- Meier analysis. The cumulative 5-year survival rate of the early surgery group ( ) (77.8%) was significantly higher than that of the observation group (58.3%). However, the prognosis in 4 cm-observation group ( ) was almost same as in early surgery group and estimated prognosis curve of Japanese normal population based on Life Table for Japan; therefore the prognosis was significantly lower in 5 cm-observation group ( ) (p<0.0001). Dotted line: normal population based on Life Table for Japan Fig cm 5cm 5 4cm cm 5cm 2 AAA 5cm 5cm 6

5 Time after operation (mo) Fig. 5 Survival curves after elective operation, using Kaplan- Meier analysis. The operative mortality rate was 0.6% in the patients who received elective surgery. There was no statistical significance in the cumulative survival rate after operation between the early surgery group ( ) and the additional elective surgery after observation ( ) (76.8% and 75.1% in 5-year survival rate, prospectively). Dotted line: normal population based on Life Table for Japan. 5cm 5cm cm 5cm prospective 5cm 5cm 2 randomized controlled trial RCT 3, cm 5.5cm AAA 5 5cm RCT 6, 7 RCT 8 4cm 5cm 5cm 4cm 4 2 watchful waiting AAA 10cm 9 10, 11 CT computed tomography 12 PET positron emission tomography 13, 14 AAA 5cm 5cm 7

6 United Kingdom Small Aneurysm Trial Participants: Longterm outcomes of immediate repair compared with surveillance of small abdominal aortic aneurysms. N. Engl. J. Med., 346: , Lederle, F. A., Wilson, S. E., Johnson, G. R., et al.: Immediate repair compared with surveillance of small abdominal aortic aneurysms. N. Engl. J. Med., 346: , Brewster, D. C., Cronenwett, J. L., Hallett, J. W. Jr., et al.: Guidelines for the treatment of abdominal aortic aneurysms. Report of a subcommittee of the Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. J. Vasc. Surg., 37: , Pretre, R. and Turina, M. I.: Facts, at last, on management of small infrarenal aortic aneurysms. Lancet, 352: , Powell, J. T. and Greenhalgh, R. M.: Clinical practice. Small abdominal aortic aneurysms. N. Engl. J. Med., 348: , UK Small Aneurysm Trial Participants: Health service costs and quality of life for early elective surgery or ultrasonographic surveillance for small abdominal aortic aneurysms. Lancet, 352: , Sakalihasan, N., Limet, R. and Defawe, O. D.: Abdominal aortic aneurysm. Lancet, 365: , Wang, D. H. J., Makaroun, M. S., Webster, M. W., et al.: Effect of intraluminal thrombus on wall stress in patientspecific models of abdominal aortic aneurysm. J. Vasc. Surg., 36: , Fillinger, M. F., Racusin, J., Baker, R. K., et al.: Anatomic characteristics of ruptured abdominal aortic aneurysm on conventional CT scans: Implications for rupture risk. J. Vasc. Surg., 39: , Hofmann, L. K., Zou, K. H., Costello, P., et al.: Electrocardiographically gated 16-section CT of the thorax: Cardiac motion suppression. Radiology, 233: , Sakalihasan, N., Hustinx, R. and Limet, R.: Contribution of PET scanning to the evaluation of abdominal aortic aneurysm. Semin. Vasc. Surg., 17: , Defawe, O. D., Hustinx, R., Defraigne, J. O., et al.: Distribution of F-18 fluorodeoxyglucose (F-18 FDG) in abdominal aortic aneurysm: High accumulation in macrophages seen on PET imaging and immunohistology. Clin. Nucl. Med., 30: ,

7 Is It Valid to Follow up Abdominal Aortic Aneurysms Smaller Than 5 cm in Diameter? Tetsuo Watanabe, Akira Sato, Eiji Hashizume, Hitoshi Goto, Kazuyoshi Handa, Daijirou Akamatsu, Hiroko Sato, Takuya Shimizu, Yoshiyuki Nakano and Susumu Satomi Division of Advanced Surgical Science and Technology, Tohoku University Key words: Abdominal aortic aneurysm, Rupture, Prognosis, Decision making Background: We have performed elective surgery for abdominal aortic aneurysm (AAA) in accordance with our policy that 5 cm is the best threshold for repair of AAA. We conducted a retrospective study to determine whether our policy is valid in all our patients with AAA. Methods: All 260 patients who presented at Tohoku University Hospital with AAAs 4 cm between 1996 and 2003 were reviewed. We examined the size of the aneurysm at the first presentation, operation for AAA, length of survival and cause of death. We divided patients into two groups. One was the patients who received early surgery and the other is those who were observed and follow up. The latter group was further divided in two subgroups: the 4 cm-observation group in which the size of the aneurysm was smaller than 5 cm in diameter and the 5 cm-observation group in which the size of aneurysm was larger than 5 cm at first presentation. We investigated the outcome and compared the groups. Results: Among these patients, 125 patients (48.1%) underwent early elective operation (early surgery group) and 135 patients (51.9%) were not offered operative treatment (4 cmobservation group: 92, 5 cm-observation group: 43). Almost all patients in the early surgery group had an AAA of 5 cm or greater. In 52 cases in the observation group, additional elective surgery was performed during the follow-up period, and all of those 52 patients had an AAA of 5 cm or greater. Rupture of the aneurysm occurred in 14 cases in the observation group and all ruptured aneurysms had reached 5 cm. No rupture occurred in aneurysms smaller than 5 cm in diameter. The cumulative incidence of probable rupture was significantly higher in the 5 cm-observation group than in the 4 cm-observaton group (p<0.0001). The cumulative 5-year survival rate of the early surgery group (77.8%) was significantly higher than that of the observation group (58.3%). However, the outcome in the 4 cm-observation group was almost same as in the early surgery group and the estimated prognosis curve of the Japanese normal population based on Life Table for Japan; therefore the outcome was significantly poorer in the 5 cm-observation group. The operative mortality rate was 0.6% in the patients who received elective surgery and there was no statistical significance in the cumulative survival rate after operation between the early surgery group and the additional elective surgery after observation (76.8% and 75.1% in 5-year survival rate, prospectively). There was also no statistical significance in the outcome after operation between the 4 cm-observation group and the 5 cm-observation group (74.8% and 78.6% in 5- year survival rate, prospectively). Conclusion: From our present study, it is valid that AAA smaller than 5 cm in diameter should be observed and followed up. Jpn. J. Vasc. Surg., 15: 3-9,