A hemorrhagic cyst is a fluid-filled sac on the ovary that contains blood from bleeding inside the cyst wall. It’s a type of functional cyst, meaning it forms as a normal part of the menstrual cycle rather than from abnormal cell growth. Most hemorrhagic cysts are harmless, cause no symptoms, and resolve on their own within six to eight weeks.
How Hemorrhagic Cysts Form
Every month, one of your ovaries develops a small fluid-filled follicle that releases an egg during ovulation. After the egg is released, the empty follicle collapses and transforms into a structure called the corpus luteum, which produces hormones to support a potential pregnancy. During this transformation, new blood vessels grow into the follicle wall and penetrate the inner lining. Sometimes these new blood vessels bleed into the cyst cavity, filling it with blood. That’s a hemorrhagic cyst.
Hemorrhagic cysts can also form when a follicular cyst (one that didn’t release its egg) develops internal bleeding the same way. Either type is considered functional because the cyst originated from the normal machinery of ovulation, not from a tumor or abnormal tissue.
Women taking blood-thinning medications or those with clotting disorders have a higher risk of developing hemorrhagic cysts, since their bodies are less able to stop the small amount of bleeding that occurs naturally during cyst formation.
Common Symptoms
Many hemorrhagic cysts are discovered incidentally on an ultrasound done for another reason. When symptoms do occur, the most common is acute pelvic pain on one side. The pain is often sharp and can come on suddenly, typically in the second half of the menstrual cycle after ovulation has occurred. Some women also notice irregular periods.
If a hemorrhagic cyst ruptures, symptoms can intensify quickly. Rupture typically causes sudden, sharp pain in the lower abdomen or back, sometimes with vaginal spotting, bloating, or nausea and vomiting. In rare cases, the bleeding can be significant enough to cause dizziness or faintness, which signals that blood is collecting in the abdominal cavity.
One unusual feature of ruptured hemorrhagic cysts is that the pain can migrate. Blood released into the abdomen may travel upward and irritate the diaphragm, producing chest or upper abdominal pain that mimics completely unrelated conditions like gallbladder inflammation. This can initially confuse even experienced clinicians.
How It Looks on Ultrasound
Hemorrhagic cysts have a distinctive appearance on ultrasound that helps doctors identify them. The most common pattern is a fine, lace-like network of thin strands inside the cyst, often described as a “fishnet” or reticular pattern. These strands are fibrin, a protein the body produces during clotting. On color Doppler imaging (which detects blood flow), these internal strands show no blood flow, which helps confirm they’re clot material rather than solid tissue or actual dividing walls within the cyst.
This appearance matters because it allows radiologists to distinguish a hemorrhagic cyst from more concerning findings. Endometriomas (cysts caused by endometriosis) can look similar because they also contain old blood. On MRI, both types may appear bright on certain imaging sequences. The key difference is that hemorrhagic cysts are short-lived, so the blood inside them doesn’t have time to develop the concentrated, dark deposits of old iron-containing pigment that characterize endometriomas. If there’s any doubt, a follow-up ultrasound in a few weeks usually settles the question, since a hemorrhagic cyst will shrink or disappear while an endometrioma persists.
Cancer Risk Is Very Low
If you’ve seen the word “cyst” on a report and felt a wave of anxiety, this is the section you’re looking for. A large study published in JAMA Internal Medicine found that women with cysts containing low-level echoes (the ultrasound category that includes hemorrhagic cysts) had no significantly increased risk of ovarian cancer compared to women with completely normal-looking ovaries. In women under 50, zero cancers were identified in this group. In women 50 and older, the three-year cancer risk was roughly 18 per 1,000, still far lower than the risk associated with complex cysts (65 per 1,000) or solid masses (102 per 1,000).
That said, context matters. A cyst that looks hemorrhagic in a premenopausal woman is almost always benign. In a woman well past menopause who is no longer ovulating, a hemorrhagic-looking cyst is unusual because there’s no follicular activity to produce one. In that situation, doctors treat the finding with more suspicion and may recommend surgical evaluation.
Follow-Up Guidelines by Size
The Society of Radiologists in Ultrasound has published clear recommendations for managing hemorrhagic cysts found on imaging in women of reproductive age:
- 3 cm or smaller: No follow-up needed. These may not even be mentioned in the imaging report.
- Between 3 and 5 cm: Should be noted in the report but still don’t require follow-up imaging.
- Larger than 5 cm: A repeat ultrasound in 6 to 12 weeks is recommended to confirm the cyst is resolving.
For women in early postmenopause (who may still occasionally ovulate), any hemorrhagic-appearing cyst warrants a follow-up ultrasound in 6 to 12 weeks regardless of size.
Treatment and Resolution
Most hemorrhagic cysts require no treatment at all. Smaller cysts typically resolve on their own within six to eight weeks as the body reabsorbs the blood. During that time, over-the-counter pain relievers can help manage discomfort if needed.
Surgery becomes a consideration in a few scenarios: when a cyst is very large, when it doesn’t resolve on follow-up imaging, when rupture causes significant internal bleeding, or when the cyst causes the ovary to twist on its blood supply (a condition called ovarian torsion). These situations are uncommon. When surgery is needed, it’s usually performed laparoscopically through small incisions and involves removing the cyst while preserving the ovary.
Effect on Fertility
Hemorrhagic cysts do not cause infertility. Because they’re functional cysts, their presence actually signals that your ovaries are going through the normal steps of ovulation. The cyst forms as a byproduct of the very process that releases an egg each month. This is different from conditions like polycystic ovary syndrome, where many small cysts develop alongside hormonal imbalances that can interfere with regular ovulation. A hemorrhagic cyst on one side doesn’t prevent the other ovary from ovulating normally, and even the affected ovary typically returns to its usual function once the cyst resolves.
Warning Signs of Rupture
Most hemorrhagic cysts either resolve silently or cause only mild, temporary pain. Rupture that requires medical attention is uncommon but recognizable. Seek emergency care if you experience sudden sharp pelvic pain along with any of the following: severe nausea and vomiting, fever, heavy vaginal bleeding, or feeling faint or dizzy. Dizziness and faintness in particular suggest significant blood loss into the abdominal cavity, which may require intervention to stop the bleeding.