From painful cramps to fluctuating hormones, women’s bodies undergo significant changes each month. Ovarian cysts may form in response to the menstrual cycle, often going unnoticed.   Â
These cysts, or growths, develop on or inside the ovaries. So are ovarian cysts dangerous? For the large majority of women the answer is no. But a small number cause complications that need urgent care, and it is worth knowing which is which. Here is what the evidence says:
What are Ovarian Cysts?
An ovarian cyst is a small, fluid-filled sac that develops inside the ovary or on its surface. Ovarian cysts are extremely common. In one study of more than 33,000 women, close to half had an adnexal cyst on ultrasound, and roughly 63 percent of those resolved on their own. Most cause no symptoms at all and need nothing more than time.
Symptoms of Ovarian Cysts
Many ovarian cysts go undetected until they are large enough to cause symptoms, like these:
- Pelvic pain
- Dull ache or sharp pain in your back or in the area below the belly button
- Feeling of fullness in your lower belly
- Bloating
- Pain during sex
- Painful or irregular periods
- Difficulties passing stool
- Increased frequency of urination
Will an ovarian cyst cause back pain?
Yes, in some cases a cyst may cause back pain – often a dull aching sensation or sharp pain.
How can you tell if an ovarian cyst has burst?
A ruptured cyst may go undetected just like an intact one, but most women experience a sudden, sharp pain in their lower belly or back when a cyst bursts. This may be followed by vaginal spotting, bloating, and continued discomfort.
When to Seek Emergency Care
Most cysts resolve quietly. Two complications are genuine emergencies, and both are treated in an emergency department, not in an imaging clinic.
Ovarian torsion. When a cyst grows large enough, usually around 5 cm or more, the ovary can twist on the ligaments holding it and cut off its own blood supply. This is the one to know, because a delay can cost the ovary. Watch for sudden severe pain on one side of the lower abdomen or pelvis, pain that comes and goes or radiates to the back or flank, and nausea or vomiting alongside it.
A ruptured or bleeding cyst. Rupture usually causes sudden sharp pain on one side, often starting during sex or exercise. Most settle on their own. If a cyst bleeds significantly the blood collects inside the abdomen where you cannot see it, so the warning signs are feeling faint or lightheaded, a racing heart, cold clammy skin or pallor, and pain that worsens rather than eases.
Call 911 or go to the nearest emergency room if you have severe or worsening one-sided pelvic pain, if you feel faint or your heart is racing, or if you have a fever with pelvic pain. Do not wait for an appointment, and do not book a scan instead. Heavy or unusual vaginal bleeding is not typical of a ruptured cyst, but it is worth having your physician evaluate it.
Can Ovarian Cysts Be Cancerous?
Most are not. A simple cyst, meaning round and fluid-filled with a thin smooth wall, no solid parts inside and no blood flow within it, is the reassuring picture. Simple cysts under 6 cm carry less than a 1 percent risk of being cancer, and single-chamber cysts under 10 cm are usually benign at any age.
The features that make a radiologist look harder are solid components, nodules growing along the wall, thick internal walls, an irregular outline, size over 10 cm, free fluid in the abdomen, and brisk blood flow within the solid parts. A single thin internal wall is far less concerning than a solid nodule with blood flow in it. Those are not the same finding.
Age matters as much as appearance. It is the single most important independent risk factor, and a cyst found after menopause deserves follow-up regardless of how simple it looks.
How an Ovarian Cyst Is Actually Evaluated
There is a lot of confusion about which scan answers this question, so here is the real pathway.
Pelvic ultrasound comes first. Transvaginal ultrasound is the recommended first-line imaging study for a suspected or incidentally found pelvic mass. The probe sits close to the ovaries and shows size, whether the cyst is fluid-filled or solid, whether there are internal walls or growths, and how much blood flow is present. Most cysts are fully characterised at this step and need nothing further.
Blood work sits in context. CA-125 can be raised in ovarian cancer, but also by endometriosis, fibroids, infection, menstruation and pregnancy. It is not a stand-alone cancer test.
MRI comes in only when ultrasound cannot settle it. Somewhere between 18 and 31 percent of these masses stay indeterminate after ultrasound. For those, a dedicated pelvic MRI with and without contrast is the problem-solving study, scored with a standardised system called O-RADS MRI. Note the word dedicated: that is a targeted pelvic exam with specific sequences and contrast timing, which is a different study from a screening whole-body scan.
A pathologist makes the diagnosis. No scan of any kind proves a mass is or is not cancer. MRI does not show individual cells, because no scanner does. It shows how tissues behave in a magnetic field, which lets a radiologist tell fat from fluid from blood from solid tissue. Those features correlate with risk. Confirming cancer requires tissue examined under a microscope after surgery.
Where a Whole-Body MRI Fits, and Where It Does Not
We would rather be straight with you than sell you something on a false premise.
A screening whole-body MRI is not an ovarian cancer screening test, and we will not present it as one. Routine ovarian cancer screening is actually recommended against for women at average risk with no symptoms. The U.S. Preventive Services Task Force gives it a Grade D, because screening has not been shown to reduce deaths from ovarian cancer and false positives lead to surgery in women who turn out not to have cancer. Women with an inherited high-risk syndrome such as a BRCA mutation are a separate group who should be managed by a specialist team.
What a whole-body scan can genuinely do is find something incidentally, as part of a broad structural look at 13 organ systems. If it shows a lesion near an ovary, the right next step is a dedicated pelvic ultrasound to characterise it. Most such findings turn out to be ordinary benign cysts, and some resolve on repeat imaging. That is a real benefit and a real limit, stated together. You can read more in our health library entry on ovarian cysts and in our honest look at what incidental findings actually are.
If you have pelvic pain, bloating, or a change in your cycle, a screening scan is not the right first step. See your physician. If you have any of the emergency signs above, go to an emergency department. If you want a broad structural baseline and understand what screening does and does not deliver, schedule your scan or talk to our team first.
This article is for general education and is not medical advice. Talk with a qualified clinician about your own symptoms.
Frequently asked questions
Are ovarian cysts dangerous?
Usually not. Most ovarian cysts are simple fluid-filled sacs that cause no symptoms and resolve on their own within a few months. In one large study close to half of women had a cyst on ultrasound and roughly 63 percent of those resolved without treatment. The exceptions worth knowing about are torsion, where a larger cyst causes the ovary to twist and lose its blood supply, and rupture with significant internal bleeding. Both are emergencies.
How do I know if an ovarian cyst is serious?
Appearance and age both matter. A simple cyst with a thin smooth wall, no solid parts and no internal blood flow is reassuring, and simple cysts under 6 cm carry less than a 1 percent risk of cancer. Solid components, wall nodules, thick internal walls, size over 10 cm, free fluid or brisk blood flow prompt a closer look. Age is the strongest single risk factor, so a cyst found after menopause warrants follow-up even when it looks simple.
Can an MRI tell if an ovarian cyst is cancerous?
No scan can prove that. MRI does not image individual cells; it shows how tissues behave in a magnetic field, which helps a radiologist separate fat, fluid, blood and solid tissue. Those features correlate with risk but do not diagnose cancer, which requires tissue examined under a microscope after surgery. MRI also is not the first test: transvaginal ultrasound is first-line, and a dedicated pelvic MRI is reserved for masses ultrasound cannot settle.
When should I go to the emergency room for an ovarian cyst?
Go straight to an emergency department, or call 911, for sudden severe one-sided pelvic pain, pain with nausea and vomiting, feeling faint or lightheaded, a racing heart with cold clammy skin, or a fever with pelvic pain. These can indicate ovarian torsion or a cyst bleeding internally. Do not wait for an appointment and do not book a scan instead.
Does a whole-body MRI screen for ovarian cancer?
No, and we would not describe it that way. There is no evidence that whole-body MRI detects ovarian cancer earlier or improves survival, and routine ovarian cancer screening is recommended against for average-risk women without symptoms because false positives lead to unnecessary surgery. What a whole-body scan can do is find a lesion incidentally, and the correct next step then is a dedicated pelvic ultrasound.
Sources
- Ovarian Cyst
- ACR Appropriateness Criteria Clinically Suspected Adnexal Mass, No Acute Symptoms: 2023 Update
- Ovarian Cancer: Screening
- Ovarian Torsion
- Ovarian-Adnexal Reporting Data System Magnetic Resonance Imaging (O-RADS MRI) Score for Risk Stratification of Sonographically Indeterminate Adnexal Masses
