In ultrasound, “adnexa” refers to the structures on either side of the uterus, primarily the ovaries and fallopian tubes. If you’ve seen this term on an ultrasound report or heard it from your doctor, it’s simply the medical shorthand for this area of the pelvis. When a report says “adnexa unremarkable” or “normal adnexa,” it means nothing unusual was found in the ovaries, tubes, or surrounding tissue on that side.
What the Adnexa Includes
The word “adnexa” comes from Latin and means “accessory structures.” In gynecology, it specifically refers to the uterine adnexa: the two ovaries, the two fallopian tubes, and the ligaments that hold them in place. Each side of the pelvis has its own set, so your report may describe the “right adnexa” and “left adnexa” separately.
The ovaries sit near the entrance to each fallopian tube and are connected to the uterus by ligaments. They produce eggs and hormones like estrogen and progesterone. The fallopian tubes extend from the upper corners of the uterus toward each ovary, serving as the passageway where fertilization typically occurs. On a standard ultrasound, the ovaries are almost always visible. The fallopian tubes, however, are not normally visible because they’re too thin and blend in with surrounding tissue. Tubes only show up on ultrasound when something is wrong, such as fluid buildup (a condition called hydrosalpinx), which makes them appear swollen and sausage-shaped.
Why Your Doctor Ordered an Adnexal Ultrasound
Pelvic ultrasound to evaluate the adnexa is one of the most common imaging studies in gynecology. It’s performed in both symptomatic and asymptomatic women of reproductive and menopausal age. Common reasons include pelvic pain, abnormal bleeding, bloating or abdominal distension, and routine gynecologic screening. It’s also a key tool in early pregnancy to confirm the pregnancy is located inside the uterus rather than in a fallopian tube.
For women trying to conceive, adnexal ultrasound is used to count antral follicles, the small fluid-filled structures in the ovaries that indicate egg reserve. During this count, the sonographer measures all follicles between 2 and 10 millimeters in diameter across both ovaries. This number helps fertility specialists assess ovarian reserve and plan treatment.
Transvaginal vs. Transabdominal Approach
There are two main ways to image the adnexa. Transabdominal ultrasound uses a probe on the outside of your lower belly, requires a full bladder, and uses a lower-frequency signal (3.5 to 5 MHz) that can scan a wide area. Transvaginal ultrasound uses a narrow probe inserted into the vagina after you’ve emptied your bladder, operating at a higher frequency (up to 10 MHz) that produces much sharper images of nearby structures.
For adnexal evaluation, transvaginal ultrasound is significantly more accurate. Studies comparing the two approaches found that transvaginal imaging has a higher detection rate for adnexal masses, ectopic gestational sacs, and subtle changes in blood flow. It can also identify findings earlier in pregnancy. Transabdominal ultrasound is still useful for getting a broader view of the pelvis, especially when a mass is large, but for detailed adnexal assessment, the transvaginal approach is the standard.
What Normal Adnexa Look Like
A normal adnexal ultrasound shows two ovaries with smooth borders and a size appropriate for your age. Ovarian volume changes significantly throughout life. It rises from about 0.7 mL at age 2 to a peak of roughly 7.7 mL around age 20, then gradually declines to about 2.8 mL around menopause. In reproductive-age women, you’ll often see small follicles within the ovaries, which is completely normal and reflects the monthly cycle of egg development.
During the first half of a menstrual cycle, one follicle typically grows larger than the rest (becoming the “dominant follicle”) before releasing an egg. After ovulation, the remaining structure, called a corpus luteum, can appear as a small cyst with thick walls. Both of these are normal, expected findings that sometimes get flagged on reports but don’t represent disease.
Common Adnexal Findings
The majority of adnexal masses found on ultrasound are functional or benign. Here are the most common types:
- Simple cysts: Fluid-filled sacs with thin walls and no internal structures. In premenopausal women, simple cysts smaller than 5 centimeters are almost always physiological (related to normal ovulation) and typically resolve on their own within three menstrual cycles, requiring no follow-up. In postmenopausal women, small simple cysts under 5 cm also carry a very low risk of malignancy.
- Endometriomas: Cysts filled with old blood, sometimes called “chocolate cysts,” associated with endometriosis. They have a characteristic ground-glass appearance on ultrasound.
- Dermoid cysts: Also called mature teratomas, these benign growths can contain fat, hair, and even teeth. They often have a distinctive mixed appearance with bright echoes from the fat and calcium inside.
- Hydrosalpinx: A fluid-filled, blocked fallopian tube that appears as an elongated, sausage-shaped structure. Since normal tubes aren’t visible on ultrasound, seeing a tube-like structure in the adnexa is itself a finding worth investigating.
- Ectopic pregnancy: A pregnancy implanted outside the uterus, most commonly in a fallopian tube. On ultrasound, this can appear as a ring-shaped structure in the adnexa (called the “tubal ring sign”), which has a 95% positive predictive value for ectopic pregnancy. A ring of blood flow around this structure on color Doppler further supports the diagnosis.
How Masses Are Classified
When a sonographer finds an adnexal mass, they assess several features to determine whether it looks benign or potentially malignant. A widely used system called the IOTA Simple Rules provides a structured way to do this, looking for specific benign features (B rules) and malignant features (M rules).
Features that suggest a mass is benign include: a single fluid-filled compartment with no solid parts, any solid component smaller than 7 millimeters, the presence of acoustic shadows (which suggest dense tissue like a fibroma), a smooth multilocular cyst under 10 cm, and no detectable blood flow within the mass. Features that raise concern for malignancy include: an irregular solid tumor, fluid in the abdomen (ascites), four or more finger-like projections (papillary structures) inside the cyst, an irregular multilocular solid mass 10 cm or larger, and very high blood flow.
If only benign features are present, the mass is classified as likely benign. If only malignant features are present, further workup is needed. When features from both categories are present, or neither applies, the result is considered inconclusive and additional evaluation, often with a specialist ultrasound or MRI, is the next step.
What “Adnexal” Means on Your Report
When reading your ultrasound report, you may see phrases like “left adnexal cyst,” “right adnexal mass,” or “bilateral adnexal findings.” These are location descriptors telling you which side of the pelvis something was found, not a diagnosis on their own. The report will usually go on to describe the size, shape, internal characteristics, and blood flow of whatever was seen.
A finding described as a “complex adnexal mass” means the structure has both fluid-filled and solid components, which warrants closer evaluation. A “simple adnexal cyst” is almost always benign. The size matters too: masses under 5 cm with simple features are rarely concerning, while larger or more complex masses typically get follow-up imaging or further assessment to rule out anything serious.