Analysis of Expansion Patterns in 4-4.9 cm Abdominal Aortic Aneurysms

Our objective was to analyze the growth pattern of 4-4.9 cm infrarenal abdominal aortic aneurysms (AAAs). We used an observational, longitudinal, prospective study design. We followed 4-4.9 cm AAAs with 6-monthly abdominal computed tomographic (CT) scans (January 1988-August 2004). AAA growth was defined as an increase in aortic diameter ≥2 mm in each surveillance period. We established the aortic expansion pattern in AAA with three or more CT scans as continuous, discontinuous. The latter includes at least one period of nongrowth ( 0.05). The eccentric thrombus was associated with a greater incidence of continuous growth ( p = 0.05), with no influence of aortic calcification ( p > 0.1). The expansion of 4-4.9 cm AAA is mostly irregular and unpredictable. We have not found any modifiable risk factors which influence their growth pattern. The eccentric distribution of the thrombus is associated with continuous expansion.