Definition of Adnexal Cyst
An adnexal cyst is a fluid-filled structure located in the adnexa—the anatomical region encompassing the ovaries, fallopian tubes, and surrounding connective tissues. 1
Anatomical Location and Classification
- Adnexal cysts arise from structures within the adnexa, which includes the ovaries, fallopian tubes, broad ligament, and adjacent peritoneal tissues 2, 3
- These cysts can be categorized morphologically as simple (unilocular with smooth walls and no solid components) or complex (containing septations, solid components, or papillary projections) 1
Types of Adnexal Cysts
Functional/Physiologic Cysts
- Most simple cysts in premenopausal women are functional in nature and resolve spontaneously 1
- Hemorrhagic cysts demonstrate characteristic spiderweb-appearing or retracting clot with peripheral vascularity on ultrasound 1
Nonfunctional Benign Cysts
The American College of Radiology identifies specific benign cyst types with characteristic imaging features 1:
- Endometriomas: Display low-level internal echoes, mural echogenic foci, or nonvascular solid attenuating components 1
- Teratomas (dermoid cysts): Show echogenic attenuating component or small horizontal interfaces on ultrasound 1
- Hydrosalpinges: Appear as tubular cystic masses with or without folds 1
- Peritoneal inclusion cysts: Cystic masses conforming to underlying pelvic spaces, located adjacent to or surrounding a functioning ovary 1
- Paraovarian/paratubal cysts: Account for approximately 6% of surgically managed adnexal masses in pregnancy 1
Pregnancy-Specific Cysts
- Hyperreactio luteinalis presents as bilateral ovarian enlargement with multiple theca lutein cysts, typically in the third trimester, and spontaneously regresses after delivery 1
Clinical Significance
- Simple cysts have an exceptionally low malignancy risk (<0.4% in premenopausal women and 0.3-0.4% in postmenopausal women) 1, 4
- Approximately three-quarters of incidentally identified adnexal masses in pregnancy are simple cysts <5 cm 1
- Among adnexal masses requiring surgical management, dermoid cysts are most common (32%), followed by cystadenomas (19%), endometriomas (15%), and functional cysts (12%) 1
Diagnostic Characteristics
- A simple cyst is defined as an anechoic, unilocular fluid collection with smooth thin walls and no solid or vascular components 1, 5
- Transvaginal ultrasound is the essential initial imaging modality for characterizing adnexal cysts 1, 4
- Color or power Doppler should be included to differentiate true solid components from debris and to assess vascularity 1, 4