A 26-year-old woman came to a gynecologist for a regular check-up. She has no complaints. Per vaginum: the uterus lies in anteflexion, not enlarged, dense, mobile, painless. On the left from the uterus in the area of uterine appendages there is a mobile painless outgrowth that can be moved independently from the uterus. On the right the appendages cannot be detected. What additional investigation would be informative for diagnosis clarification?