Abdominal Aorta Size

Because of a history of diverticulitis (hospitalized twice) and a recent attack of same, last August my doctor ordered a CT scan of the abdomen and pelvis.  Colon was fine but a "mild aneurysmal of the proximal abdominal aorta - 2.6 centimeters in diameter" was detected. My doctor sent me to a vascular doctor who wants me to have an ultra sound or CT scan yearly to detect any changes.  He was able to show me the results on a computer screen.
A couple months later, I had a "HealthFair USA" ultrasound screening that reported "No Aneurysm" - "largest portion of aorta 1.5 cm".
Why would there be the discrepancy?
Is there a chart of aorta sizes based on size/weight/age of person? (I'm small and colonoscopies require a pediatric scope.)
Websites indicate aneursyms under 3 centimeters isn't usually reported.
Should I restrict any weights - my gyno mentioned it.
"HealthFair USA" screening detected ASI "mild abnormality"  84 AC - Is that something the vascular doctor should know?
FYI - 64 years young, 110 pounds and very active.
Thanks in advance for your attention.

[Cleveland Clinic]

There is no evidnece based on what you provided that you have an aneurysm.  Aneurysms usually enlarge over time, this is why you doctor wants to reimage you to be 100% sure.  2-3 centimeters, depending on patient height and size are normal measurements.  Being that you are small 1.5 to 2.6 seems normal.  Remember that a lot of these measuremets have many errors in them and this is why reimaging is very useful.