I also had this come up at my 20 week scan. It was a stressful time, especially because we had come back as high risk for Down's at 12 weeks, and had got the all clear for that and were hoping for smooth sailing from then on, only to be told at 20 weeks about the echogenic bowel.
As you may know, echogenic bowel can be associated with chromosomal disorders, such as Down's, Edward's and Patau's. But it is overwhelmingly likely not to be any of those; on its own, if it's the only marker, it would be very unlikely to be one of the trisomies. In my case, we knew it couldn't be, as we had had NIPT at 13 weeks which came back all clear.
The other thing is that can be caused by a congenital infection, so hopefully you will have been offered TORCH screening? And it is also associated with cystic fibrosis, so you may be offered a test to see if either you or your partner are carriers.
In my case, all of these tests came back all clear, and so the echogenic bowel remained unexplained. We ended up having lots and lots of growth scans as a result and it seems to have cleared up, and so we can only assume it was nothing, simply a result of the baby swallowing some blood. (I didn't have a bleed I'm aware of, although I did fall over on my bum about a week before the 20 week scan, which could possibly have caused an internal bleed). I'm 37 weeks now and there has been no further indication of anything wrong with the baby, and he is growing like an absolute beast (80th percentile on my last scan!)
I am someone who does a huge amount of reading and research when things like this happen, and from what I could work out, echogenic bowel on its own, as a sole marker, is rarely a sign of anything very worrying. Further, it seems it is being picked up and more and more as our ultrasound technology gets better and more sensitive. One of the later scans I had said the bowel was bright, but not as bright as bone, which it would need to be to be called echogenic, and the sonographer suggested that at one time, their equipment simply wouldn't have seen it.
So there are lots of reasons to be positive. I hope it all works out well for you. I read this, when it was happening to me, and I found it incredibly reassuring and helpful, I highly recommend it:
www.freerepublic.com/focus/f-news/1630478/posts?page=51
It's by a leading American sonographer who thinks that our advanced sonography is, in many cases like yours and mine, terrifying mothers of healthy babies for no real reason. That was certainly my experience!