What Causes Swollen Genitals Post Open Heart Surgery?

Hello, I have a question about my Dad. He had open heart surgery Feb. 5th this year. For some reason his genitals have swollen, and although he says there is no pain, it makes him very uncomfortable. His surgeon started him on Lasix with potassium about a week ago, but it has made very little difference. He has a follow up appointment in the morning, but I would appreciate any insight you have. Thank you.