When the diameter of the abdominal aorta should be considered as abnormal? : a new ultrasonographic index using the wrist circumference as a body build reference

Purpose: To use US to evaluate the normal values of aortic diameter (AD), stratifying the population by age, gender and body build, as measured using wrist circumference (WC). Materials and methods: Between April 2010 and February 2012, consecutive patients >= 30 years of age, without history of abdominal aortic aneurysm (AAA) were prospectively enrolled. They underwent an abdominal ultrasonography for reasons other than aorta evaluation. AD was measured at the infrarenal (AD(1)), intermediate (AD(2)), and iliac bifurcation (AD(3)) levels: a diameter >= 3 cm was considered as an aneurysm. The maximal aortic diameter (AD(max)) was measured for AAA patients. WC was measured; AD/WC ratio was calculated and presented in percentage: the range of normal values was obtained excluding AAA cases and calculated as mean +/- 1.96 x standard deviation. Pearson correlation coefficient was used. Results: We recruited 1200 patients, 15 (1.25%; age range = 64-86 years) had AAA. AD ranges of the other patients were: AD(1) = 0.74-1.84 cm, AD(2) = 0.78-1.85 cm, and AD(3) = 0.68-1.76 cm for females; AD(1) = 0.86-2.02 cm, AD(2) = 0.91-2.08 cm, and AD(3) = 0.84-1.95 cm for males. AD(2)/WC ratio of non-AAA patients range was 4-15%, with only one outlier at 18%, while AD(max)/WC ratio of AAA patients range was 15-35% (p < 0.001). ADs were significantly correlated with WC (r = 0.253, p < 0.001 for AD(1), r = 0.318, p < 0.001 for AD(2) and r = 0.280, p < 0.001 for AD(3)). Conclusion: The definition of normal AD should consider body build. An AD(2)/WC ratio of 15% may be regarded as a threshold to differentiate AAA- from non-AAA patients. Patients with AD(2)/WC values comprised between 12% and 15% may be at risk for AAA.