I am just going to add that the definition of aneurysm varies by age. A 50mm Aorta in an 80-year old would be considered normal, but indication for replacement in a 40-year old.
This article has a useful table:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3461294/
The article says:
According to the classic understanding, a diameter increase of 50% marks the borderline between ectasia and aneurysm—the threshold at which a dilated ascending aorta/root should be considered an aneurysm, therefore, is
This article has a useful table:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3461294/
The article says:
According to the classic understanding, a diameter increase of 50% marks the borderline between ectasia and aneurysm—the threshold at which a dilated ascending aorta/root should be considered an aneurysm, therefore, is
~40 mm in a 20-year-old
~ 45 mm in a 40-year-old
~ 50 mm in a 60-year-old
~ 55 mm in an 80-year old