We saw the pediatric neurologist today. He told us that they did not see anything additional on the MRI, which is excellent news as it means we are much more likely to be in the category with less dire outcomes. If you're interested, this paper provides a pretty good summary both of their own findings and the literature. So at this point it's just a waiting game - we will do another MRI post-birth, and hope that they don't find anything additional on that either (the fetal MRI can be a bit of a guessing game b/c the fetus is moving around so it's hard to get perfect images).
We have another u/s in 2.5 weeks to check on the status of the kidneys; the would consider early delivery if those progress, as fluid in the kidneys if it builds up too much can cause a dearth of amniotic fluid (which is essentially the baby's urine), and can also cause kidney damage. I am hoping that since truffle's kidney size was relatively stable between 18 and 28 weeks that it will remain that way - having to deliver him prematurely is definitely not ideal, I think that the extra cooking time is even more important for him than someone without brain abnormalities. I have a feeling that as long as the post-birth MRI comes back clear, we won't know for a long time what we're dealing with, as a lot of the issues that these kids have do not necessarily show up in the early days.
One thing from the paper that I referenced that took us by surprise was that in the group with isolated agenesis, 60/87 chose to terminate, and in the group with additional brain abnormalities, 70/88 chose termination.