A millimeter or two is pretty small and within the margin of error. Mine has been all over the map, from 3.9 cm to 4.6. Depends on your local hospital lab, the tech doing the scan and the doctor doing the interpretation. I believe one thing the local lab will not do is is give a smaller measurement from one they have previously given. I live in Maine and go to my local (small) hospital. In 2009, the ultrasound came back at 4.3cm, increasing from 3.9cm. Like you, I was upset and went to a large, well known Boston hospital and had a 3-D CT scan with contrast. It came through at 4.6cm. The chief of surgery met with me (20 minutes) and pretty much said I should entertain open AAA surgery since I wasn't a great candidate for EVAR. Well, I became really concerned because as you know, open AAA surgery is a big deal with lots of risks. I decided to get a second opinion, so I got a copy of my CT scan on a DVD from the Boston hospital and began research on the best hospitals in the country who deal with many AAA surgeries. I settled on Mayo in Rochester, MN simply because they have a well deserved reputation and do over 200 AAA surgeries annually. I made an appointment with the Mayo Vascular department for a second opinion and it turned out to be a great move. Where the Boston Vascular spent 20 minutes with me and did not actually show me my own CT scan, the Mayo Vascular intake doctors spent a full couple of hours with me actually showing me how they measure an aneurysm using the same CTscan DVD from the Boston hospital. The Mayo interpretation was that my aneurysm had not changed from the initial CT scan in 2006 of 3.9/4.0cm and that it did not measure 4.6cm. I now fly out to Mayo once a year for a consult and ultrasound scan and there has been no change. My comfort level with the folks at Mayo is high and while it costs $500/$600 annually to fly out and stay one night, to me its worth the peace of mind that comes from knowing I'm at the right place.