@imautistic In an earlier post and this one, you mentioned fatigue and hypothyroidism, so I'm guessing they are trying to pinpoint the cause. The thyroid gland can and does change over time, so maybe they are looking for that, or maybe on further review they did not think the earlier ultrasound gave a clear enough image. That has happened to me at least twice, and the test had to be repeated. I'm not a professional, but I think there could be a correlation between the thyroid diseases and the celiac blood test results as well.

As for the weak positive on the celiac test, have the doctors said they will be doing a biopsy? Do you know which blood test(s) they did?