How accurate is the transabdomen and transvaginal ultrasound for early detection of ovarian cancer?

Not very: Unfortunately, there is no good screening for ovarian cancer. Ultrasound will show a mass if there is one and may help characterize it as likely benign or malignant. This, with blood test and recognizing symptoms, might help with managment of a mass that is already there, but not in early detection. Notify your doctor if you have persistent bloating, change in bowel or bladder habits, or pain.

Quite accurate: In patients with strong family history of ovarian ca, screening with ultrasound and blood test is indicated since it's difficult to pick up early ovarian cancer. The ultrasound can differentiate between a simple cyst or a complex cyst ( mixed cystic and solid structure) which may warrant further testing and treatment. It can also evaluate the size and grow of the cyst.