Vaginal ultrasound

So this is gonna sound strange but I don't know what's the best plan or action.

I have to have an empty bladder for the vaginal ultrasound checking the length of my cervix but then I'm required to do a urine sample for the appointment that's 10 mins after when they talk you through the results but sometimes there's a wait so it could be quite abit longer than 10 mins.

I just don't want the sample sat to long and giving inaccurate results as I was thinking doing a sample right before the ultrasound so that I've got my sample and an empty bladder but I'm just not sure and if I should just have the ultrasound, drink as much as I can between next appointment then try pee really silly dilemma 🙄😂