I had a girlfriend before with bloody UTI (Urinary Tract Infection) three times a year (from intimacy). I'd like to understand whether bloody UTI is caused by thinner bladder or more aggressive forms of bacteria? I was so afraid it may infect her kidney so I just left her as I couldn't take the pressure. Now looking for another woman I'd like to make sure it won't happen again.. and I'm curious of the technicalities of bloody UTI. When you (women) have UTI.. it's normally not bloody.. for you.. what causes UTI to be blood.. what you think?