Yes, ovarian cysts can have blood flow, and the pattern of that blood flow is one of the key things doctors look at on ultrasound to determine what type of cyst you have and whether it’s concerning. Most benign cysts show blood flow only around their outer edges, while blood flow inside a cyst, particularly through solid areas or along internal walls, draws more scrutiny. Understanding what these patterns mean can help you make sense of your ultrasound report.
Why Blood Flow Matters on an Ultrasound
A standard ultrasound shows the size, shape, and internal structure of a cyst, but it can’t tell doctors much about how the tissue is behaving. That’s where Doppler ultrasound comes in. Doppler measures the movement of blood through and around a cyst by detecting shifts in sound waves as they bounce off red blood cells. The result is a color overlay on the ultrasound image: areas with blood flow light up in red or blue, while areas without flow stay gray.
Doctors evaluate three things about the blood flow: whether it’s present at all, where it’s located (around the outside versus inside the cyst), and how easily blood moves through the vessels. That last measurement is captured in two numbers you might see on your report. The resistive index (RI) reflects how much the blood vessels resist flow, and the pulsatility index (PI) captures how much flow fluctuates with each heartbeat. Lower numbers mean blood is flowing more freely through vessels with less resistance, a pattern more commonly seen in cancerous growths.
Blood Flow in Common Benign Cysts
The vast majority of ovarian cysts are benign, and their blood flow patterns reflect that. In a study of cystic ovarian lesions in adolescents, 85% showed only peripheral blood flow, meaning the vessels were around the outside of the cyst rather than running through it. This included simple fluid-filled cysts, hemorrhagic cysts (those containing blood from a small bleed), and benign tumors called cystadenomas. About 15% of benign cystic lesions showed no detectable blood flow at all.
The corpus luteum cyst, which forms naturally after ovulation, has a particularly distinctive look on Doppler. It displays intense blood flow in a complete ring around its wall, a pattern radiologists call the “ring of fire.” This can look alarming on screen because the color signal is so bright and prominent, but it’s completely normal. The corpus luteum is actively producing hormones to support a potential pregnancy, so it needs a rich blood supply. This ring of fire pattern can also appear with an ovarian ectopic pregnancy, so doctors interpret it alongside other findings like pregnancy test results and the location of a gestational sac.
Other benign growths have their own typical patterns. Dermoid cysts (mature teratomas, which contain tissue like hair or fat) tend to have organized, low-resistance blood flow. Ovarian fibromas, which are solid benign tumors, often show very little peripheral vascularity. Cystadenofibromas, another benign type, typically display low to moderate blood flow.
How Endometriomas Differ From Other Cysts
Endometriomas, sometimes called “chocolate cysts,” form when endometrial tissue grows on the ovary and fills with old blood. Their blood flow pattern is unique enough that researchers have described it as a potential “hemodynamic signature.” Compared to dermoid cysts, endometriomas show higher resistance to blood flow within the cyst itself (RI of 0.57 versus 0.54 for dermoids). This happens because the chronic inflammation of endometriosis disrupts normal blood vessel organization, making the vessels stiffer and less efficient.
At the same time, the surrounding pelvic blood vessels on the affected side actually show lower resistance than expected, likely because the body dilates nearby vessels to compensate for the inflammatory process. This combination of high resistance inside the cyst with lower resistance in the surrounding area is fairly specific to endometriomas and can help distinguish them from other types of cysts that look similar on a standard grayscale ultrasound.
When Blood Flow Raises Concern
The blood flow pattern that gets the most attention is internal vascularity running through solid portions of a growth. In one study comparing benign, borderline, and malignant ovarian tumors, blood flow inside the tumor was detected in about 90% of both borderline and malignant cases, compared to only 53% of benign tumors. Cancerous growths develop their own new blood vessel networks to fuel rapid cell growth, and these newly formed vessels tend to be irregular and “leaky,” allowing blood to flow through with very little resistance.
This is where the RI and PI numbers become particularly useful. Malignant tumors averaged an RI of 0.39 and a PI of 0.58, while benign tumors averaged an RI of 0.61 and a PI of 1.05. Using a cutoff of RI below 0.6 as a flag for malignancy, one study found that 100% of malignant tumors fell below that threshold, compared to only about 11% of benign ones. A PI cutoff below 0.8 correctly identified about 91% of malignant tumors while misclassifying only about 9% of benign ones.
Advanced cancers that have spread within the ovary tend to score 3 or 4 on a standardized color score scale (where 1 is minimal and 4 is abundant flow), reflecting their dense, chaotic blood vessel networks. Tumors that have metastasized to the ovary from elsewhere in the body, such as the stomach or breast, often show a characteristic “lead vessel,” a single large blood vessel that penetrates from the outer edge deep into the center of the mass.
Absent Blood Flow and Ovarian Torsion
While most conversations about cyst vascularity focus on how much flow is present, the absence of blood flow carries its own significance. Ovarian torsion occurs when the ovary twists on its supporting ligaments, cutting off circulation. The process is progressive: venous drainage gets blocked first, causing the ovary to swell with trapped blood. As swelling increases, arterial flow gets compressed too, eventually leading to tissue death if the ovary isn’t surgically untwisted.
On Doppler, doctors compare blood flow in the affected ovary to the opposite side. But the interpretation isn’t straightforward. The ovary receives blood from two separate arterial sources, so even a partially twisted ovary can still show some flow. In the adolescent study mentioned earlier, three cases of confirmed torsion showed completely absent blood flow, but absence of flow also appeared in some ordinary cysts that weren’t twisted at all. The ovary can also spontaneously untwist before the ultrasound, making flow appear normal despite an ongoing problem. This is why doctors can’t rely on Doppler alone to rule torsion in or out; they weigh it alongside symptoms like sudden severe pelvic pain and nausea.
Reading Your Ultrasound Report
If your report mentions “peripheral vascularity” or “circumferential flow,” that’s the most common and generally reassuring pattern for a benign cyst. Terms like “avascular” or “no internal vascularity” for a simple cyst are also typical and not worrisome on their own. A “ring of fire” description points to a corpus luteum cyst, which is a normal part of the menstrual cycle.
Language that prompts closer follow-up includes “internal vascularity within solid components,” “central vascularity,” “low-resistance flow,” or specific RI and PI values that fall below the 0.6 and 0.8 thresholds. These findings don’t automatically mean cancer. More than half of benign tumors in some studies showed at least some internal blood flow. But when internal vascularity combines with other suspicious features, like irregular solid areas, thick internal walls, or fluid in the pelvis, it strengthens the case for further evaluation with additional imaging or surgical removal for biopsy.
Blood flow is one piece of a larger puzzle. Doctors combine Doppler findings with the cyst’s size, internal appearance, your symptoms, your age, and sometimes blood markers to arrive at an overall assessment. A single finding in isolation rarely tells the whole story.