Hi I am Dr Fahim and I will answer your query . . . I have gone through your question and understood your concerns. Its nice to hear that your father is doing well after renal transplant. Testicular swelling after a year of transplant is unlikely associated with transplant operation. It appears to be hydrocele, a collection of fluid in scrotal sac. A benign conditon and completely treatable with surgery. You need to get his ultrasound scrotum done to reach at an accurate diagnosis. Hydrocele surgery involves opening the testicular layers, draining the fluid and plicating the layers to prevent further accumulation. You need to get him reviewed by general surgeon or urologist, who after diagnosis will guide you about course of action. Do rate my answer, if you like it. If there are any further Qs you are most welcome Regards