No single test diagnoses an ovarian cyst. A pelvic or transvaginal ultrasound can find it and describe what it looks like. A second scan six to twelve weeks later usually confirms what that appearance means, because most ovarian cysts are identified by how they change, not by a single image.
Most ovarian cysts are found when nobody is looking for them
If nobody was investigating you for an ovarian cyst when one turned up, you are in the majority. Ovarian cysts are most often picked up on imaging ordered for something else: an abdominal scan for pain that turned out to be digestive, a study of the kidneys, a routine pregnancy scan, or a fertility baseline scan.
The scale of this is documented. In a study published in the journal Radiology in January 2018, researchers reviewed abdominal and pelvic CT (computed tomography) examinations from 42,111 women. They found that incidental adnexal cysts (cysts in the region of the ovary and fallopian tube) were reported in 6.6% of women over the age of 15. Every cyst described as simple in appearance turned out to be benign, with a 95% confidence interval of 99.6 to 100%.
That figure describes what happens across a large population followed over years. It is not a promise anyone can make to you on the day of your scan, and this page will highlight that difference throughout.
A widely cited review in the Cleveland Clinic Journal of Medicine in August 2013 outlined three ways a clinician can respond to an incidentally found ovarian cyst: reassure, reassess, or refer. That framing is worth carrying with you, because everything below is about how your doctor decides which of the three applies to you.
Being found by accident is not a sign that your ovarian cyst was missed, neglected, or left to grow. It is simply the most common way ovarian cysts come to light.
The tests used to diagnose an ovarian cyst
None of these tests diagnoses an ovarian cyst on its own. Each test answers a narrow question, and the diagnosis is assembled from the answers. Most women have only the first two or three. The final column is the one worth reading, because it usually goes unsaid in the appointment.
Test
What It Involves
What It Can Show
What It Cannot Tell You
Pelvic examination
A first, quick assessment by hand.
Tenderness or a swelling large enough to feel.
Whether a cyst is present at all. Most are far too small to feel.
Pelvic ultrasound, abdominal approach
Looking at the ovaries through the lower abdomen.
Whether a cyst is present, roughly how large it is, and whether it is fluid-filled.
Fine detail. Bowel gas and body habitus can obscure the view.
Transvaginal ultrasound
A closer view using a slim probe placed in the vagina.
The clearest available picture of the ovary, cyst wall, contents and blood flow.
Whether the cyst is harmless. It describes appearance but does not confirm its nature in every case.
Pregnancy test
Establishing whether you are pregnant.
A result that can change what the finding means entirely.
Anything about the cyst itself.
Blood tests, including tumour markers
Contributing to a risk assessment.
A result interpreted alongside the scan, your age and menopausal status.
Whether you have an ovarian cyst or whether any cyst found is cancer.
MRI (magnetic resonance imaging)
Characterising tissue when the ultrasound is inconclusive.
What a cyst is likely to be made of when ultrasound could not settle it.
A definitive answer in every case. It narrows the possibilities.
CT (computed tomography)
Usually ordered to investigate something else altogether.
That a cyst exists, often as an unexpected finding.
Enough detail to characterise an ovarian cyst properly. Ultrasound generally does this better.
Diagnostic laparoscopy (keyhole surgery)
Looking directly at the cyst and sometimes removing tissue for examination.
The cyst itself and tissue that a pathologist can examine if a sample is removed.
Nothing further without considering the risks. It is surgery, not a routine diagnostic step.
Ultrasound: the first and usually the only scan needed for an ovarian cyst
Two approaches exist, and they are not competing options so much as different distances from the ovary. An abdominal ultrasound passes sound waves through the lower abdomen. It is quick, needs no preparation beyond a comfortably full bladder, and suits a cyst large enough to sit above the pelvis. A transvaginal ultrasound places a slim probe in the vagina, much closer to the ovary, which is why it produces a more detailed picture of the two.
Because the resolution is better, a transvaginal scan is usually what a gynaecologist wants when the question is specifically about an ovary. It is offered rather than imposed. You can decline it, ask for a chaperone, ask for the abdominal approach instead, and ask the sonographer to stop at any point. None of that marks you out as a difficult patient, and none of it is unusual.
It is worth saying plainly what the scan feels like, because very few pages will. The probe is narrower than a speculum; it is covered and lubricated, and most women describe pressure rather than pain. It does not require sedation, it does not affect fertility, and it does not affect the hymen in the way that is often assumed. If you are anxious, say so before you undress rather than after, because the room is easier to adjust to then.
What an ovarian cyst scan can and cannot tell you
The scan is genuinely good at some questions and genuinely unable to answer others. Knowing which is which is the difference between leaving the appointment frustrated and leaving it informed.
Your Question
Can the Scan Answer It?
What Gives You the Answer
Is there an ovarian cyst?
Yes, in most cases.
The scan itself. This is where it is best seen.
How big is it?
Yes.
The measurement on the report. What that measurement means is a separate question.
Is it simple or complex?
Usually, yes.
The described appearance, which sorts cysts into broad groups rather than providing a definitive diagnosis.
Is it causing my pain?
No, not by itself.
Whether the pain follows the cyst over time. A cyst on a scan is not proof that it is the source of the pain.
Will it go away?
No, not from a single scan.
A repeat scan. This is the most common way to assess whether the cyst resolves.
Is it cancer?
No, not definitively.
Appearance, a structured risk score and specialist assessment where indicated.
The flat version of that table is this: no ultrasound can confirm that an ovarian cyst is harmless on the day it is found. It can show features that make a harmless cyst overwhelmingly likely, but that's not the same claim, and it's why follow-up exists at all. Where your question is what the pain itself is likely to be, that is covered separately in our guide to one-sided pelvic pain.
Your report will use specific words for what was seen, and those words carry meaning that is not obvious from the page. We cover reading an ovarian cyst ultrasound report in its own guide rather than decoding it here. A report describing something other than a single ovarian cyst is a separate topic again, covered in our polycystic ovaries story.
Size matters, but it is one factor among several rather than a verdict, and thresholds differ before and after menopause. Ovarian cyst size has its own guide. Where the worry is cancer, that sits with the risk score and the guide to whether an ovarian cyst can turn into cancer.
Blood tests in ovarian cyst diagnosis: what they are and are not for
No blood test can find an ovarian cyst. That is worth stating, because much published material implies otherwise by listing blood tests alongside imaging as though they did the same job.
The most useful blood test on the pathway is also the least discussed. A pregnancy test is often done early, and it is not a formality. Pregnancy changes what a cyst on the ovary is likely to be, because a corpus luteum cyst (the cyst that forms after an egg is released and which supports an early pregnancy) is an expected finding rather than a problem. It also changes what is safe to do next. If you are asked for one, that is the reason.
Tumour markers, of which CA-125 is the one most women are offered, contribute to risk assessment rather than diagnosis. The number is read alongside the scan appearance, your age and your menopausal status, and it is not interpreted alone. Our CA-125 guide explains what the result means in practice, including why it can rise for reasons unrelated to cancer.
When an MRI or CT scan is used for an ovarian cyst
Most women with an ovarian cyst never need either. The honest way to describe them is as a sequence rather than a choice you make: ultrasound answers the question in the great majority of cases, and second-line imaging exists for the minority where it does not.
An MRI is the usual next step when an ultrasound has been performed and remains inconclusive. It better characterises tissue composition, which is often missing when the ultrasound description sits between categories. It involves no radiation.
A CT scan sits at a different point on this pathway. It is usually the scan that found the ovarian cyst by accident rather than one ordered to assess it, for the reasons set out earlier on this page. It is not the tool of choice for characterising an ovarian cyst, and being sent for an ultrasound after a CT has already shown a cyst is a step forward rather than a repetition.
Why diagnosing an ovarian cyst often means waiting for a second scan
This part of the pathway causes the most distress and is explained the least. The wait isn't an administrative delay while someone decides something about you. Time is part of the diagnostic test.
What the Scan Shows
What Usually Happens Next
Why
A simple cyst below the size at which follow-up is advised
Often nothing further.
Cysts of this description are almost always functional and resolve without intervention.
A simple cyst above that threshold
A repeat scan after an interval.
Resolution confirms it was functional. Persistence means it was not necessarily a functional cyst and may need further assessment.
A cyst with complex features
A repeat scan and often a risk assessment alongside it.
Appearance narrows the possibilities without settling them.
A cyst found after menopause
Closer assessment, usually sooner.
The threshold for further investigation is lower once the ovaries are no longer cycling.
A cyst found during pregnancy
Monitoring throughout the pregnancy in most cases.
Many are expected findings that resolve as the pregnancy progresses.
A cyst found on a fertility baseline scan
Reassessment before or during the treatment cycle.
The finding may change the timing of treatment rather than the diagnosis.
A functional ovarian cyst (one that forms as part of the normal menstrual cycle) is confirmed by resolution. A single image cannot confirm that, which is why a second scan is a diagnostic step rather than a holding pattern. The Royal College of Obstetricians and Gynaecologists, in its joint green-top guideline on suspected ovarian masses in premenopausal women published in November 2011, notes that simple cysts of this kind are very likely to be physiological and almost always resolve within about three menstrual cycles.
The interval varies. Six to twelve weeks is common, and some situations require longer gaps. Anyone quoting a single universal number is simplifying, because the interval is a clinical judgment based on your scan, your age, and your symptoms.
If the cyst is still there on the second scan, that is information rather than bad news. It rules out a functional explanation and shifts the assessment to appearance and risk. Waiting is not itself dangerous, with one set of exceptions, set out below.
How the risk of an ovarian cyst is scored
Radiologists and gynaecologists do not assess an ovarian cyst by impression alone. A structured risk score is applied to what the scan describes, so that the same appearance leads to the same recommendation regardless of who is reading it. Your report may or may not quote it directly.
Our guide to ovarian cyst risk scoring explains what the score contains, how its categories work, and which features move a cyst from one category to another.
Diagnosing an ovarian cyst in pregnancy or during fertility treatment
Women who are pregnant or in fertility treatment have more ovarian cysts found than other women. The counterintuitive part is that this is largely about detection rather than incidence. If you are scanned every few days during a treatment cycle, or several times during pregnancy, findings that would otherwise appear and resolve unseen get seen.
In pregnancy, the diagnostic question shifts. A cyst on the ovary in early pregnancy is often a corpus luteum cyst doing exactly what it is supposed to do, and the usual approach is monitoring rather than investigation. Some tests used outside pregnancy are interpreted differently or not used at all. Ovarian cysts in pregnancy are covered in more depth in their own guide.
On a fertility baseline scan, a cyst found at the start of a cycle is common and is usually assessed by how it behaves over the following days. What that means for the treatment cycle itself is covered in our guide to cysts from fertility treatment. Serial ovarian scanning is routine in a fertility unit, and follicular monitoring explains how it's done.
When an ovarian cyst needs urgent assessment rather than a scheduled scan
Seek urgent medical care the same day if you have:
Sudden, severe pain on one side of the lower abdomen
Pain with vomiting, or pain severe enough to stop you standing straight
Fever alongside abdominal pain
Feeling faint, fainting, or a racing heartbeat
Abdominal swelling that comes on rapidly
The decision you are actually making is whether to wait for a booked appointment or go now. Go now if any of the above applies. A scheduled follow-up scan is for a cyst that behaves predictably, and these symptoms mean it is not.
Two complications account for most of these presentations. One is ovarian torsion, where the ovary twists and its blood supply is affected. The other is rupture, where a cyst bleeds or leaks. Both are assessed urgently rather than at the next available slot, and both are covered in detail in the guides to ovarian torsion and ruptured ovarian cysts. Do not wait to see whether the pain settles overnight, and do not travel a long distance to a particular clinic when a nearer emergency department can assess you sooner.
What to ask about your ovarian cyst scan report
Appointments are short, and reports are technical. These five questions cover most of what women say they wish they had asked.
Was the cyst described as simple, or were other features noted?
Which ovary is it on, and has anything changed since a previous scan?
Are you recommending a repeat scan, and when?
What would change the plan before that scan is due?
Can I have a copy of the report? You are entitled to ask for one, and it is worth having before any second opinion.
Speak to someone about your scan report
If you have a scan report and are not sure what it is telling you, a consultation to go through it is a reasonable use of an appointment. For most women a general gynaecologist is the right person to see. If you are trying to conceive, a fertility specialist at Cloudnine Fertility can review the report and advise what it means for your timing.
FAQs
Your questions, clearly answered
Find clear, trusted answers to the most common questions about IVF—designed to guide and support you every step of the way.
How are ovarian cysts diagnosed?
There is no single test. A pelvic or transvaginal ultrasound can find the ovarian cyst and describe its size and appearance. A repeat scan usually confirms what it is, because many ovarian cysts are identified by how they change rather than by one image.
Which test is best for detecting an ovarian cyst?
For most women, a transvaginal ultrasound gives the clearest view of the ovaries and is the most reliable way to detect an ovarian cyst. An abdominal ultrasound is used instead when a transvaginal scan is unsuitable or declined, or when the cyst is large.
Can a blood test diagnose an ovarian cyst?
No. Blood tests support the assessment rather than making the diagnosis. A pregnancy test can change what the finding means, and tumour markers such as CA-125 contribute to risk scoring rather than showing whether a cyst is present.
Can an ultrasound tell if an ovarian cyst is cancerous?
Not on its own. The scan describes features that raise or lower concern, and those features feed a structured risk score. Appearance alone does not confirm that an ovarian cyst is benign, which is why some are rescanned and a few referred.
Why do I need a second scan for my ovarian cyst?
Because many ovarian cysts are diagnosed by what they do over time rather than by one image. A cyst that has resolved by the second scan was functional, meaning it formed as part of the normal menstrual cycle. The interval is a clinical judgement.
How long does it take to diagnose an ovarian cyst?
The cyst itself is usually identified in a single scan appointment. Determining what type of ovarian cyst it is can take a few weeks to a few months, because the answer depends on whether it changes.
Do I need a transvaginal scan to diagnose an ovarian cyst?
A transvaginal scan usually gives the clearest view of the ovaries, but it is offered rather than imposed, and you can decline it. An abdominal ultrasound is the alternative. Tell the sonographer if you would prefer that, or ask for a chaperone.
Can an ovarian cyst be missed on a scan?
Yes, this happens. Small ovarian cysts can be missed, bowel gas can obscure the view on an abdominal scan, and some are only visible at certain points in the cycle. It is one reason a repeat scan is arranged when symptoms continue.
