I've never self cathed, Daisy. When I went to the hospital they cathed me once and never again in the 12 days I was there. When I asked if I was retaining a lot, they said "a little, but they don't like to cath too often, as you become dependent on it.
And dats all I know.
I empty by squeesing my bladder till empty. I have to go potty every 4 hrs though, so I must retain some...and I drink during the night too..