my sister in law got an ultrasound and it said her ovary was swollen and filled with fluid. what could be causing this? they said there was no cyst there It is probable that the ovary itself is not filled with fluid, but rather she has a CYST on her ovary that is fluid-filled. Cysts are very common in reproductive-aged women. Cysts often form from the corpus luteum...the pocket from which the monthly egg is expelled. Most heal on their own, some rupture and some need medical intervention. Only her doctor will know the best course of treatment. | 