6 week ultrasound - what should I expect to see?

To cut a long story short, I've been in and out of hospital over the past week with lower right abdominal pain, and a possible ectopic pregnancy. I had an ultrasound at 5 weeks, but only a 'sac' of some kind was seen and the Dr couldn't confirm that this was a healthy pregnancy as it was so small (measuring smaller than 5 weeks at that point!). I am due to have another ultrasound on Thursday (I will be 6 weeks!), what should I expect to see? I presume a gestational sac, yolk sac and featal pole, but should this all be visible so early on? Please do post any pictures of your 6 week scans! Thank you...