Why is it that women have a field of medicine to themselves and not men?

I was remembering that I have to make my gynecologist appointment and it got me thinking. Women, and women only, see gynecologists. Is there a male specific field of medicine that only men would go to the doctor for. My co-worker mentioned a urologist, but I looked up the definition and it says both men and women can see one (even though they do deal with men’s genitals and prostrate).