An adnexal cyst is a fluid-filled sac that forms within the tissues adjacent to the uterus. The adnexa refers to the pelvic structures connected to the uterus, including the ovaries, fallopian tubes, and supporting ligaments. Cysts are common and typically benign, but they require evaluation for proper identification.
Defining Adnexal Cysts
The adnexa are situated on both sides of the uterus within the pelvic cavity. Growths, or masses, can arise from various tissues in this complex anatomical region. While an adnexal cyst most often originates from the ovary, it can also stem from the fallopian tube or surrounding supportive tissues.
A true cyst is a fluid-filled sac with thin walls, differentiating it from a solid mass. Other growths in this region, collectively called adnexal masses, include solid tumors, abscesses, or an ectopic pregnancy. Distinguishing between a simple cyst and a complex mass is important for determining the cause and necessary management.
Cyst formation typically involves fluid accumulation or the failure of a structure to resolve normally. Ovarian cysts frequently develop as a direct consequence of the normal hormonal changes of the menstrual cycle. For example, cysts arising from the fallopian tubes, such as a hydrosalpinx, occur when the tube becomes blocked and fills with fluid.
Differentiating Cyst Types
Adnexal cysts are broadly categorized into functional (or physiological) and pathological (or non-functional) groups. Functional cysts are the most common type, directly related to the monthly ovulatory cycle. These cysts generally resolve on their own without the need for medical intervention.
Functional cysts include follicular cysts, which form when the dominant follicle fails to release an egg and continues to grow. Corpus luteum cysts develop after ovulation if the remnant structure seals off and fills with fluid or blood instead of breaking down. These physiological cysts are usually small, typically under five centimeters, and have thin, smooth walls visible on imaging.
Pathological cysts do not arise from the normal menstrual cycle and require more careful monitoring. Endometriomas, often called “chocolate cysts,” are filled with old blood and are a manifestation of endometriosis within the ovary. Dermoid cysts originate from germ cells and contain various types of tissue, such as hair, fat, or bone.
Other pathological types, such as cystadenomas, arise from the surface cells of the ovary and can be large and filled with serous or mucinous fluid. Imaging helps distinguish these types: simple cysts appear thin-walled and fluid-filled, while complex masses may show solid components, thick internal walls (septations), or surface growths.
Recognizing Symptoms and Diagnosis
Many adnexal cysts are asymptomatic and are often discovered incidentally during a routine pelvic exam or imaging for an unrelated issue. When symptoms occur, they are typically related to the cyst’s size or its physical effect on surrounding organs. Common complaints include a dull ache or pressure in the pelvis, abdominal bloating, or a feeling of fullness.
Some women may also experience changes in their menstrual cycle, such as irregular or heavier periods, or pain during sexual intercourse. A sudden onset of severe, sharp pelvic pain accompanied by nausea or vomiting requires immediate medical attention. This may indicate a complication like ovarian torsion, where the ovary twists on its supporting ligaments and cuts off its blood supply, or a cyst rupture causing internal bleeding.
The primary diagnostic tool used to evaluate an adnexal cyst is a pelvic ultrasound, often performed transvaginally to provide clear images. Ultrasound assesses the cyst’s size, internal consistency (simple fluid or complex components), and shape. Features like thick septations, solid areas with blood flow, or irregular borders are concerning and may prompt a referral to a specialist.
Blood tests aid in risk assessment, particularly when malignancy is suspected or in postmenopausal women. The CA-125 blood test measures a protein that can be elevated in ovarian cancer, but it is not a definitive test. High levels of CA-125 can also be caused by benign conditions such as endometriosis, uterine fibroids, or pelvic inflammatory disease.
Treatment and Long-Term Monitoring
Treatment depends on the patient’s age, menopausal status, the cyst’s size, and its appearance on imaging. For small, simple, fluid-filled cysts in premenopausal women, the most common approach is watchful waiting. Monitoring involves repeating the pelvic ultrasound after a specified period to confirm resolution, as most functional cysts resolve spontaneously within one to three menstrual cycles.
Medical management may be recommended for women who have recurring functional cysts. Hormonal birth control pills can suppress ovulation, thereby preventing the formation of new follicular and corpus luteum cysts. This method prevents future cyst development, but does not shrink an already existing cyst.
Surgical intervention is reserved for cysts that are large, have concerning features on ultrasound, or cause persistent, severe symptoms. Cysts that are complex, show solid components, or are greater than ten centimeters typically warrant removal. Surgery is also performed immediately for acute complications like ovarian torsion or rupture.
Surgeons generally favor minimally invasive procedures, such as laparoscopy, which uses small incisions and specialized instruments to remove the cyst while preserving the ovary (cystectomy). Open surgery, or laparotomy, is sometimes necessary for very large masses, when cancer is suspected, or if the anatomy is obscured by scar tissue.