A hemorrhagic ovarian cyst is a fluid-filled sac on the ovary that has bled internally, filling with blood and clot material. These cysts are almost always benign and develop as part of the normal menstrual cycle. Most resolve on their own within two to three menstrual cycles without any treatment.
How Hemorrhagic Cysts Form
Every month, an ovary produces a small fluid-filled structure called a follicle, which releases an egg during ovulation. After the egg is released, the follicle transforms into a temporary hormone-producing structure called the corpus luteum. Sometimes, a blood vessel in the wall of this follicle or corpus luteum breaks, and blood leaks into the cyst cavity. That internal bleeding is what makes it “hemorrhagic.”
This can happen at two points in the cycle. A follicular cyst forms when the follicle doesn’t release its egg and keeps growing. A corpus luteum cyst forms after ovulation, when the empty follicle seals off and fills with fluid. Either type can bleed internally. If fertilization occurs, the corpus luteum persists for several weeks before eventually dissolving, and central hemorrhage can happen during that breakdown process as well.
What It Feels Like
Many hemorrhagic cysts cause no symptoms at all and are discovered incidentally during an ultrasound done for another reason. When symptoms do occur, the most common is a dull, one-sided pelvic pain, typically on the side of the affected ovary. Some people describe it as a deep ache or pressure in the lower abdomen.
If the cyst ruptures, the pain shifts dramatically. It becomes sudden, sharp, and can be severe. Ruptured cysts can also cause bleeding into the pelvic cavity, which may lead to lightheadedness or more widespread abdominal pain. For uncomplicated ruptures, pain typically resolves within a few days with over-the-counter pain relief. Severe or ongoing symptoms after rupture, especially heavy bleeding, can require more urgent care.
How It Looks on Ultrasound
Hemorrhagic cysts have a distinctive appearance on ultrasound that helps distinguish them from other ovarian masses. The most common pattern is a “fishnet” or fine reticular (net-like) look, created by thin strands of fibrin (a clotting protein) stretching across the interior of the cyst. These internal strands are not blood vessels, and color Doppler imaging confirms no blood flow inside the cyst. The cyst wall itself is typically thin.
This appearance changes over time as the blood inside breaks down and is reabsorbed. An early hemorrhagic cyst may look complex and worrisome, with clot material and mixed echoes. Over the following weeks, it simplifies, shrinks, and often disappears entirely. This evolution is actually one of the most useful diagnostic clues: hemorrhagic cysts change on follow-up imaging, while other masses tend to stay the same.
How It Differs From an Endometrioma
Endometriomas (sometimes called “chocolate cysts”) can look similar at first glance, but there are reliable differences. An endometrioma contains old, thickened blood and produces a uniform “ground glass” appearance on ultrasound, with low-level echoes distributed evenly throughout. Its walls are typically thicker, sometimes with small nodules. Most importantly, endometriomas do not resolve on their own. They remain stable over time and require yearly monitoring due to a small risk of malignant transformation.
A hemorrhagic cyst, by contrast, has variable internal echoes, those characteristic fibrin strands, thin walls, and a retracting clot. It shrinks and resolves within weeks. When a cyst’s identity is unclear on the initial scan, a follow-up ultrasound at 8 to 12 weeks can usually settle the question: if it’s smaller or gone, it was hemorrhagic.
Complications to Be Aware Of
The two main complications are rupture and ovarian torsion. Rupture is more common and causes acute, sharp lower abdominal pain. In most cases, the body reabsorbs the leaked fluid and the pain fades within days. Rarely, rupture causes significant blood loss that requires more aggressive intervention.
Torsion happens when the weight of a cyst causes the ovary to twist on its blood supply, cutting off circulation. This is less common but more urgent. Torsion typically causes sudden, intense pain that may come in waves, sometimes with nausea and vomiting. Larger cysts carry a slightly higher torsion risk simply because they make the ovary heavier and more mobile.
Follow-Up and Monitoring
Current guidelines from the American College of Radiology recommend that hemorrhagic cysts in premenopausal people be re-evaluated with ultrasound at 8 to 12 weeks. This window gives the cyst enough time to either resolve (confirming it was functional) or persist (suggesting it may be something else that needs further evaluation, sometimes with MRI).
Simple ovarian cysts smaller than 5 centimeters in premenopausal people generally don’t need follow-up imaging at all, since they almost always resolve within two to three menstrual cycles. For larger cysts, follow-up tracks size and complexity. In postmenopausal people, the thresholds are lower: simple cysts larger than 3 centimeters warrant monitoring, because physiologic cysts are not expected after menopause.
When Surgery Becomes Necessary
The vast majority of hemorrhagic ovarian cysts never require surgery. Watchful waiting is the standard approach, and most cysts disappear without intervention. Surgery enters the picture in specific situations: when a rupture causes hemodynamic instability (meaning blood loss severe enough to affect blood pressure and heart rate), when a cyst continues to grow rather than shrink on serial imaging, or when torsion is suspected.
In postmenopausal patients, a cyst that increases in size or becomes more complex on follow-up scans may prompt surgical removal, especially if blood markers associated with ovarian cancer are rising. During pregnancy, surgery is considered if a cyst causes persistent pain or grows rapidly. For most premenopausal people with a straightforward hemorrhagic cyst, the management plan is simply a repeat ultrasound in two to three months to confirm it has resolved.