How to Read Your Ovary Ultrasound Report and Results

An ovarian ultrasound report describes the size, shape, and internal structure of your ovaries and any masses found on or near them, then assigns a level of concern based on what the sonographer and radiologist observed. Most reports follow a predictable format: ovarian dimensions, follicle counts, a description of any cysts or masses (including their size, wall thickness, and internal contents), Doppler blood-flow findings, and a conclusion or impression that ranks the likelihood of a problem. Understanding each section can turn an intimidating page of medical jargon into something genuinely useful.

What “Normal” Ovaries Look Like on Ultrasound

The first numbers you’ll usually see are the ovarian dimensions and calculated volume. In women of reproductive age, the average ovarian volume is roughly 6 ml, with a typical range of about 5.8 to 6.4 ml. Before puberty, ovaries are much smaller, averaging around 1.7 ml.¹ After menopause, ovarian volume shrinks substantially as the follicle supply dwindles. So a volume that would be perfectly normal in a 28-year-old could be noteworthy in a 60-year-old, and vice versa. If your report lists an ovarian volume, compare it against your age and reproductive status rather than a single universal cutoff.

Your report will also reference follicles, the small fluid-filled sacs that house developing eggs. In the early part of a menstrual cycle, these are called antral follicles and typically measure 2 to 5 mm. The total antral follicle count (AFC) declines with age: women in their mid-to-late twenties tend to have the highest counts, averaging about nine per ovary, while women over 35 may show considerably fewer.¹ One study of women with proven natural fertility found that at age 30 the antral follicle count ranged anywhere from 7 to 22, while at age 40 it ranged from 2 to 7, illustrating just how much natural variation exists.² If your report notes a specific AFC, that number is most meaningful when your doctor interprets it alongside your age and the reason you had the scan.

The Corpus Luteum and Why It Can Look Alarming

If you had your ultrasound in the second half of your menstrual cycle, after ovulation, your report may describe a corpus luteum. This is a temporary structure that forms from the follicle that released an egg, and its job is to produce progesterone to support a potential pregnancy. On ultrasound, a corpus luteum frequently contains a central fluid-filled cavity, which can make it look like a cyst. Research has shown that about 78% of corpora lutea have this cavity, and nearly 90% of women show the fluid-filled type within two days of ovulation.³

This is entirely normal and resolves on its own. By about two weeks after ovulation, only about a third of corpora lutea still show the fluid-filled cavity.³ If your report mentions a “hemorrhagic cyst” or “complex cyst” on the ovary and you are in the luteal phase of your cycle, there’s a good chance this is simply a corpus luteum doing its job. Doctors often recommend a follow-up scan in six to eight weeks to confirm it has resolved.

Simple Cysts Versus Complex Cysts

The distinction between “simple” and “complex” is one of the most important things to look for in your report, because it drives almost every downstream decision about monitoring and treatment. A simple cyst is a unilocular (single-chambered), fluid-filled sac with thin walls, no solid parts, and completely clear fluid inside. A complex cyst has additional features: internal divisions called septations, thickened walls, solid components, or debris floating in the fluid.⁴

Simple cysts in premenopausal women are overwhelmingly benign, especially when they are small. Most are functional cysts, meaning they arise from the normal process of ovulation and typically disappear within one to three menstrual cycles. Complex cysts require more careful evaluation. The more solid components, irregular septations, or blood flow a mass has, the higher the concern. But “complex” does not automatically mean cancer. Many complex cysts turn out to be hemorrhagic cysts, endometriomas, or mature cystic teratomas (dermoid cysts), all of which are benign.

Common Benign Findings You Might See

Several specific types of ovarian masses show up frequently in reports, and understanding their characteristic descriptions can save you a lot of worry.

Endometriomas: These are cysts caused by endometriosis. On ultrasound they typically appear as a single-chambered mass with smooth inner walls and a distinctive “ground glass” appearance to the internal fluid, sometimes with small bright spots (echogenic foci) in the wall.⁵ The ground-glass look comes from old, thickened blood trapped inside the cyst. If your report uses this phrase, it’s a strong clue the radiologist suspects endometriosis.
Dermoid cysts (mature cystic teratomas): These are the most common true ovarian tumors and contain a mixture of tissue types like fat, hair, and sometimes even teeth. Their ultrasound appearance varies widely, from a purely cystic mass to one with a prominent solid component, because the internal mix of tissues is so diverse.⁶ A bright, highly echogenic nodule (sometimes called a “dermoid plug” or Rokitansky nodule) is a classic sign. Despite looking complicated on ultrasound, dermoids are almost always benign.
Hemorrhagic cysts: These form when a follicle or corpus luteum bleeds into itself. They often show a lacy, web-like internal pattern that can mimic a solid mass at first glance. Repeat scanning after a cycle or two usually shows the cyst shrinking or resolving as the blood is reabsorbed.

What the Doppler Section Tells You

Many ovarian ultrasound reports include a Doppler assessment, which evaluates blood flow within and around a mass. Two numbers commonly appear: the pulsatility index (PI) and the resistance index (RI). These measure how much resistance blood encounters as it flows through the vessels feeding the mass. The basic principle is that new, disorganized blood vessels in malignant tumors tend to have lower resistance to blood flow compared to the organized vessels in benign tissue.

Research confirms that both PI and RI tend to be lower in malignant masses than in benign ones, but there is considerable overlap between the two groups. No single cutoff value is both highly sensitive and highly specific. For example, using a PI cutoff of 1.0 catches all malignancies but misclassifies more than half of benign masses as suspicious, while an RI cutoff of 0.4 is very specific for malignancy but misses half of actual cancers.⁷ This is why Doppler findings are never used alone to make a diagnosis. They’re one piece of a larger puzzle that includes the mass’s size, shape, internal structure, and your clinical history.

IOTA Simple Rules and O-RADS Scores

If your report mentions “IOTA rules” or an “O-RADS” category, the radiologist is using a standardized scoring system to estimate the likelihood that a mass is benign or malignant. These systems were developed specifically to reduce vague, inconsistent reporting and help doctors make clearer management decisions.

The International Ovarian Tumor Analysis (IOTA) simple rules classify masses based on five features suggesting benignity (B-rules) and five suggesting malignancy (M-rules). If only B-rules apply, the mass is classified as likely benign; if only M-rules apply, it’s classified as likely malignant; if rules from both groups apply or neither does, the result is inconclusive and the mass needs further evaluation. Across multiple studies, the IOTA rules can be applied to roughly 89-90% of ovarian masses, and when applicable, they achieve sensitivity for detecting malignancy in the low-to-mid 90s percent range with specificity in the mid-80s to low 90s.⁸⁹

The O-RADS (Ovarian-Adnexal Reporting and Data System) uses a numbered scale from 0 to 5, similar to how BI-RADS works for breast imaging. O-RADS 0 means the scan was incomplete, O-RADS 1 means a normal ovary with no mass, and O-RADS 2 through 5 represent increasing levels of malignancy risk. Each score comes with a management recommendation, from routine follow-up at the low end to surgical referral at the high end.¹⁰ If your report lists an O-RADS score of 2, for instance, the estimated malignancy risk is very low, and the recommendation is typically a follow-up ultrasound in several weeks to months. An O-RADS 4 or 5 carries higher concern and usually triggers referral to a gynecologic oncologist for further evaluation.

One advantage of these systems is that they give you and your doctor a shared, standardized language. Instead of a narrative paragraph that different readers might interpret differently, you get a number tied to a specific risk estimate and action plan.¹¹

Acoustic Shadowing and Other Technical Terms

Your report may describe “acoustic shadowing,” which is the dark zone that appears behind a structure that absorbs or reflects the ultrasound beam strongly. Dense materials like calcifications, teeth in a dermoid, or fibrous tissue block the sound waves, creating a shadow behind them. Acoustic shadowing is predominantly found in benign lesions, so its presence is generally a reassuring sign, though interpreting it correctly takes skill and experience.¹²

Other terms you might encounter include “anechoic” (meaning completely black, like clear fluid), “echogenic” (bright, reflecting sound back strongly), and “heterogeneous” (a mix of different textures). “Septations” are internal walls dividing a cyst into compartments. “Papillary projections” are small, finger-like solid growths protruding from the inner wall of a cyst, and these raise more concern than septations alone. “Free fluid” in the pelvis (also called fluid in the cul-de-sac) is often a normal finding, especially around ovulation, but large amounts can suggest a ruptured cyst or other process.

When the Report Mentions the Fallopian Tubes

Normal fallopian tubes are usually too thin to be seen on ultrasound, so if a tube shows up in your report, something has made it visible. The most common reason is a hydrosalpinx, a fluid-filled, dilated tube. This can result from prior infection, surgery, or endometriosis. In the context of pelvic inflammatory disease, the report may describe a thickened, fluid-filled tube or a “cogwheel sign,” which represents swollen folds along the tube’s interior. If the infection has progressed, the report may describe a tubo-ovarian abscess, seen as a complex mass with mixed solid and cystic areas that blurs the normal boundaries between the ovary and tube.¹³

Transvaginal ultrasound is actually quite good at detecting these tube-related findings, with reported sensitivity in the range of 85% to 93% and specificity of 96% to 100% for pelvic inflammatory disease.¹³ If your report mentions any of these findings, your doctor will likely discuss antibiotic treatment or further imaging.

PCOS and the Follicle Count Threshold

Polycystic ovary syndrome is one of the most common reasons women undergo ovarian ultrasound, and the report’s follicle count plays a specific diagnostic role here. The classic ultrasound finding is a high number of small follicles arranged around the periphery of an enlarged ovary. Current research suggests that the optimal threshold for identifying polycystic ovaries on ultrasound is around 19 follicles per ovary, a number that balances sensitivity and specificity well for distinguishing PCOS from normal ovaries.¹⁴

This is higher than older guidelines suggested, reflecting the improvement in ultrasound technology over the past two decades. Modern high-frequency transducers can visualize smaller follicles that older machines would have missed, which means a count that would have been considered high years ago might be within normal range now. If your report lists a high follicle count, your doctor will interpret it in conjunction with your symptoms, hormone levels, and menstrual history before making a PCOS diagnosis. Ultrasound alone isn’t enough.

Ovarian Torsion Signs

If you came to the ultrasound with acute, sudden pelvic pain, your radiologist may have been looking for signs of ovarian torsion, where the ovary twists on its blood supply. The ultrasound signs of torsion can be frustratingly subtle. Common indirect findings include an enlarged ovary, free fluid in the pelvis, peripheral follicles pushed to the edges, and absent blood flow on Doppler. But these indirect signs individually don’t have strong predictive value.¹⁵

The most specific finding is the “whirlpool sign,” a swirling appearance of the twisted vascular pedicle (the stalk carrying the blood vessels to the ovary) seen when the sonographer sweeps the probe along its axis. In one study, a twisted pedicle with a whirlpool sign was identified in all 21 patients later confirmed to have torsion. When no blood flow was visible in the twisted pedicle on Doppler, all of those patients turned out to have hemorrhagic infarction of the ovary.¹⁶ If your report mentions the whirlpool sign or absent ovarian blood flow, this is typically treated as a surgical emergency.

Why Reports Can Be Hard to Understand

Even with standardized systems like O-RADS, radiology reports remain notoriously difficult for patients to interpret on their own. Research examining how patients and caregivers interact with pelvic imaging reports found that many did not feel able to interpret or understand the contents, regardless of whether the reports used a standardized format or traditional free text. The core problem is that terms like “cystic mass with irregular septations and papillary projections” carry specific clinical meaning that requires training to decode.¹⁷

This doesn’t mean you shouldn’t try to understand your report. It means you should treat your own reading as a starting point for a conversation with your doctor, not as a final interpretation. Look for the “Impression” or “Conclusion” section at the bottom of the report first, because that’s where the radiologist distills everything into a recommendation. If you see an O-RADS score, that gives you a quick benchmark. And if any finding is followed by a recommendation for MRI or referral to a specialist, take that as a prompt to schedule a follow-up appointment rather than a reason to panic.

When MRI Comes Next

If your ultrasound report calls a mass “indeterminate” or the IOTA rules return an inconclusive result, your doctor may order a pelvic MRI. MRI is particularly good at characterizing masses that ultrasound can’t fully resolve. A systematic review found that MRI with contrast provides the highest confidence for detecting ovarian cancer, though its greatest practical contribution is actually its ability to confirm that an uncertain-looking mass is benign, sparing patients unnecessary surgery.¹⁸ In one study, MRI identified all five malignancies in a cohort while correctly classifying 94% of benign masses.¹⁹

An MRI referral doesn’t mean cancer is likely. It means the ultrasound couldn’t provide enough information to make a definitive call, and MRI offers a much better look at tissue composition. Fat, blood, fluid, and solid tissue all have distinct MRI signatures that help radiologists pinpoint whether you’re dealing with a dermoid, an endometrioma, a fibroma, or something that genuinely warrants surgical exploration.

How Age and Life Stage Change What’s Normal

The appearance of normal ovaries shifts dramatically across a woman’s lifespan. In childhood, ovaries are visible on ultrasound at all ages, and small microcystic follicles are a normal finding even in young girls.²⁰ Ovarian volume increases after about age 6, and the overall size and morphology of the ovaries change noticeably around puberty. Girls who have begun breast development show different ovarian morphology and larger ovarian volumes compared to those who haven’t.²¹

After menopause, the ovaries shrink and stop producing follicles. A simple cyst found in a 30-year-old is almost certainly a functional cyst and rarely needs any workup beyond a follow-up ultrasound. The same simple cyst in a 65-year-old postmenopausal woman, while still likely benign, will be evaluated more carefully because the absence of a menstrual cycle means functional cysts shouldn’t be forming. Complex cysts in postmenopausal women generally receive more scrutiny and faster referral than the same finding in a younger woman. Context is everything when reading these reports.

2D Versus 3D Ultrasound

Some reports may note that a three-dimensional (3D) ultrasound was used, and you might wonder if this is more accurate than a standard two-dimensional (2D) scan. For follicle counting, research comparing the two methods found no significant statistical difference in antral follicle counts between 2D and 3D ultrasound. Both correlated well with the number of eggs actually retrieved during fertility treatment.²² Three-dimensional imaging can be helpful in specific situations, like getting a better spatial view of a mass’s internal architecture or measuring ovarian volume more precisely. But for routine ovarian assessment, the two techniques perform similarly, so you shouldn’t worry if your scan was done in 2D only.