Complex cyst in the ovary on CT means that the cyst does not contain simple fluid or water. There is more complexity to the fluid. On CT, a simple cyst will have water density but a more complex cyst may have a denser fluid, nodules or septations. Pelvic ultrasound is the best way to evaluate a cyst and it’s contents, but CT may be the initial test done for another reason or pelvic pain. CT may not always show how complex a cyst really is.
A complex cyst is most commonly a cyst which contains blood in it. This is a common finding in reproductive age women. This is usually benign and resolves on its own over weeks. Sometimes hemorrhagic cysts which contain blood can bleed into the pelvis and cause pelvic pain. Usually the bleeding is minor and stops on its own. I have seen cases of more severe bleeding which requires surgery.
A complex cyst that is large, has nodules or septations becomes more concerning for cancer, although benign cysts can also have this appearance. The appearance is more concerning in post menopausal women. Ovarian cancer often presents with ascites or fluid and sometimes spread to other parts of the abdomen and pelvis.
Other benign causes for cysts include endometriosis which can cause endometriomas. This is localized form of endometriosis with repeated bleeding. Functional cysts related to the ovulation can also appear large and complex. Some cysts which are congenital or you are born with can also present in the pelvis.
I usually recommend follow up for cysts which are large or complex. Usually many functional cysts will resolve in 1-2 menstrual cycles. Complex post menopausal cysts are more concerning and it may be appropriate to recommend a surgical consultation for removal.
In some cases, a pelvic MRI will be helpful to take a closer look at the cyst and it’s contents. A cyst which has thick septations or solid nodules becomes more concerning for cancer. If I see a cyst on CT, I often recommend a pelvic ultrasound. This is one of the best ways to look at a cyst and it’s contents. A gynecologist may be involved in your care, particularly if surgery is a consideration.