Kidney trouble

When I was a little girl I was told that lady should go to the toilet whenever she passed one as that was their idea of keeping your kidneys in good working order now not so long along a doctor was talking on the TV and he said this was a very bad thing because it eventually weakens the kidneys, he said now one shouldn't go to the toilet until the bladder is full. The medics always seem to change ideas on what is good and what is not...