It depends on where the heavy petting happened and what you mean by urinary disease. I will assume that you mean heavy petting on the outside of the vagina and whether or not it can cause a urinary tract infection. I believe it is possible to cause a urinary tract infection by heavy petting, especially if the person's hand has previously been on or around the anus.
If you make sure the person's hands are clean, avoid touching around the rear end, and make sure the petter is touching the clitoris, and not the urethra, you should be all right in the future.