Can Silver Sulfadiazine Be Used For Burning During Passing Stools?

I have recently been diagnoised with rectal cancer. I have gone throught 6 weeks of radiation and chemo therapy. I am on my 3rd day after treatment and can not get relief from a constant feeling of needing to have a bowel movement. It also burns when I urinate. I have been given a medication for the burning but does not always work. I can t remember the name but it turns your urine a bright yellow/orange. I also have silver sulfadiazine for a radiation burn. Can iI use the silver sulfadiazine on the rectum. I understand from my Oncologist that it also has a radiation burn.