Scan Thursday

Cat
To rule out ectopic pregnancy. I think going on my dates that I'll only be 4+6 on Thursday. I've had a bad kidney infection and so they just want to rule out that it's not an ectopic pregnancy. I was admitted to hospital week last Monday where they announced my pregnancy. Just wondering what I can expect to see. And they haven't asked me to make sure I have a full bladder? (Not that that is very difficult) do I need to have a full bladder when I go? 
This is my 2nd pregnancy my first was born at only 24 weeks he is now a healthy 7 year old. I've mixed emotions. Excited but petrified also. 
When you're classed as a high risk pregnancy what does this entail please? 
Sorry for this post with a million questions in. Lol. Xx I'm from the UK too. Xx