Infra-renal abdominal aortic calcification volume does not predict small abdominal aortic aneurysm growth

Vascular calcification is a common finding in abdominal aortic aneurysms (AAA) however whether it predicts aneurysm expansion is controversial.

1) To establish a reproducible method of assessing AAA calcification using computed tomography (CT); 2) To investigate the association between AAA calcification and growth.

Patients were identified from a prospectively maintained small AAA surveillance database. To be included patients required at least two CT scans a minimum of 6 months apart. All patients had a maximal AAA diameter of ≤55 mm on their initial scan. Infra-renal aortic calcification volume, total infra-renal aortic volume and maximal AAA diameter were measured. Reproducibility was assessed from repeat scans performed on 31 patients. AAA growth, estimated by volume change per year, was compared between patients with baseline infra-renal aortic calcification volumes< and ≥median.

95% agreement limits (lower, upper) for intra and inter-observer error in measuring infra-renal aortic calcification volume were 0.68, 97 mm(3) and -140, 5.8 mm(3), respectively. Concordance correlation coefficients for inter and intra-observer variability in measuring infra-renal aortic calcification volume were 0.99 and 0.99, respectively. Patients with infra-renal aortic calcification volume < median (n = 44) and ≥median (n = 44) had an infra-renal aortic volume increase of 6.0 cm(3)/yr and 7.8 cm(3)/yr, respectively (p = 0.66). Mean percentage infra-renal aortic volume increase/yr was found to be 4.2 ± 6.4 and 8.9 ± 6.2 for patients with and without diabetes, respectively (p = 0.003).

Infra-renal aortic calcification volume can be assessed reproducibly from CT images. Infra-renal aortic calcification volume did not predict small AAA growth.