A bladder assessment is a good way of finding out more about how the bladder functions normally. 

Children will usually attend for a morning and will be encouraged to drink well. 

As they need a wee, they will have a bladder scan to estimate the size of the bladder.  The toilet they use will measure the amount of wee.  It will also measure the speed it comes out to give a flow graph which gives doctors and nurses useful information to suggest treatments.