Please help 18 weeks sonogram abnormal

I don't know if this is the correct place to be posting this, but I don't know where else to turn until I get the appropriate answers from my doctor. A couple days ago I posted about my sonogram for Thursday and how excited I was to find out the gender of my baby. What was supposed to be the best day of my life, turned into a complete nightmare. Going for the sonogram, The baby was in a bad position for one, them not being able to see what the baby is and two, to get all of the images for the anatomy portion of the sonogram. It started off with a strong heartbeat, which led me to believe that the baby was OK. After about 20 minutes of the sonogram technician not being able to get all of the images, she asked me to use the bathroom and walk around for about five minutes to help the baby move positions. I did exactly that and when we got back the baby had been in the same position. We both agreed that we were going to get what we need today and come back in a week or two to try and get the appropriate images again. At that point I didn't think much besides being disappointed that I didn't know what I was having. After getting home, I get a phone call from my doctors office to come into her office immediately. At that point my heart completely dropped. I left the sonogram fairly confident that everything was OK. After getting to the doctors office, She began to tell me but there was no fluid around the baby. The baby is not producing urine and had one enlarged kidney. Also from what they can see there is no bladder. The first thing I thought was, the sonogram was not complete they did not get all of the images that were required to clear me. She then told me I need to go to a specialist to confirm their findings. If this is true, why didn't they detect this at my 13 weeks sonogram? Has anybody ever been through this before? Has anybody ever heard of something like this? Any kind of feedback would be helpful at this point. I have an appointment to go to a specialist on Monday but I cannot stop thinking about this.