such as vascular prosthesis implantation or endovascular aneurysm repair (EVAR); so far, no medical therapy has been established. 7-9 Surgical treatment is highly invasive, and even elective surgery is associated with a 30-day mortality rate of 5.4%. 7 Surgical treatment is therefore indicated only for cases in which the risk of rupture is higher than the operative mortality rate.The maximum axial diameter (MAD) of the aneurysm is an indicator of rupture risk in fusiform AAA; the greater the MAD, the higher the risk of rupture. 7,8,10 In Europe and the USA, comparisons of the rate of rupture and postoperative mortality rate have led to the surgical indication of MAD ≥55 mm; in Japan, the common surgical indication is ≥50 mm, which takes body size into consideration. 7,8,11 For women, the surgical indication is sometimes taken as MAD ≥45 mm because the rupture risk in women has been reported to be 3-fold higher than in men. 11 Patients with smaller AAA (MAD <50 mm), for whom surgery is not A bdominal aortic aneurysm (AAA) is a pathological condition in which the abdominal aorta has a diameter >30 mm, or 1.5-fold greater than normal at the level of the renal artery. 1 Most AAA are asymptomatic, but once rupture occurs, the condition has a mortality rate of 65-85% and is ranked as the 16th most prominent cause of death in the USA in individuals aged ≥65 years. 2,3 In Europe and the USA, the prevalence of the condition is 2% in men aged ≥65 years, with major risk factors for morbidity including male sex, age, history of smoking, and Caucasian race. 3,4 The etiology in the majority of AAA is considered to be atherosclerosis, but a causal relationship with the typical risk factors for atherosclerosis, such as hypertension, dyslipidemia, and diabetes mellitus, remains unclear. 5 Indeed, a negative correlation with diabetes mellitus has been shown, suggesting that AAA is a pathological state distinct from atherothrombosis. 4-6The only treatment option for this condition is surgery, The maximum axial diameter (MAD) of a fusiform abdominal aortic aneurysm (AAA) is an indicator of the risk of expansion or rupture. Apart from smoking and MAD itself, few expansion risk factors have been reported. In this study, we investigated expansion risk factors for AAA.
