Dr. Keith Roach is a physician at Weill Cornell Medical College and New York Presbyterian Hospital. He writes an educational column on infectious diseases, public health and sports medicine. DEAR DR.

DEAR DR. ROACH: I am at my wit’s end and hope that you can answer this for me. I am a 76-year-old male. Next week, I’m going to have surgery in my genital area. My urologist told me to wash with ...