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Objective: Predicting which abdominal aortic aneurysms (AAA) will require surgery and which may remain stable remains a challenge. We set out to evaluate whether semi-automatic diameter measurements and finite element analysis (FEA) might predict the four-year prognosis of AAAs more precisely than standard diameter measurements. Methods: From a retrospective dataset of 97 patients with aneurysm baseline diameter of 40-50 mm, 39 AAAs remained below 55 mm in diameter for four years whilst 58 expanded beyond 54 mm within four years, or were treated surgically. Standard diameters, measured by radiologists or vascular surgeons, were recorded at baseline and at follow-up. Maximal external and luminal diameters as well as total and luminal volume were semi-automatically re-measured from 3D models based on CT images. FEA, estimating the peak wall rupture index (PWRI), was subsequently performed. Further, in 94 patients from the dataset, standard diameter growth rates between baseline and follow-up were calculated. Results: Aneurysms that would require surgery within four years were identified with 100% specificity by semi-automatic diameter, n=13 (22%), luminal diameter, n=14 (24%), PWRI, n=7 (12%), and luminal volume, n=5 (8.6%). Neither standard diameter nor total volume could reach 100% specificity. AAA diameter growth rate correlated with baseline semi-automatic diameter (r=0.39, p=9.2e-5), luminal diameter (r=0.29, p=0.005) and luminal volume (r=0.23, p=0.027) but not with PWRI (r=0.17, p=0.094), total volume (r=0.16, p=0.13), nor standard diameter (r=0.14, p=0.17). Conclusion: In AAAs with small diameters, precise, semiautomatic measurement of the maximal external and luminal diameter is able to specifically identify aneurysms requiring surgery within four years.