CA125 and Pelvic Ultrasound: How Ovarian Cancer Is Investigated

Following Ovarian Cancer Awareness Month in March, one question we hear often is how ovarian cancer is actually investigated. If you have symptoms such as persistent bloating, feeling full quickly or pelvic pain, your doctor may suggest a CA125 blood test and a pelvic ultrasound scan. Understanding what each test can and cannot tell you can make waiting for results a little easier.

What is CA125?

CA125 is a protein that can be found in the blood. Levels are often raised in women with ovarian cancer, which is why this blood test is commonly used as a first step. In the UK, a result of 35 units per millilitre or more is usually considered raised and leads to further tests.

The test itself is a simple blood sample taken from your arm. No special preparation is needed. Results usually come back within a few days, and your GP or specialist will explain what they mean for you.

What CA125 can and cannot show

A raised result does not mean you have cancer. Many harmless conditions can raise CA125 levels, including periods, pregnancy, endometriosis, fibroids, pelvic infection and some liver or bowel conditions. Because several of these affect women before the menopause, results are always interpreted carefully in that context.

Equally, a normal result does not completely rule out ovarian cancer. Some ovarian cancers, particularly at an early stage, do not raise CA125 at all. That is why your symptoms matter just as much as the number, and why an ultrasound scan is so useful alongside the blood test.

The role of pelvic ultrasound

A pelvic ultrasound uses sound waves to create images of your womb and ovaries. It is often done as a transvaginal scan, where a slim probe is gently placed in the vagina to give the clearest view. Sometimes a scan over the tummy is used as well, or instead. You can read more on our gynaecological ultrasounds page.

The scan shows the size and appearance of the ovaries and whether there is any cyst or mass. Most ovarian cysts are simple and harmless. However, certain features, such as solid areas or fluid in the abdomen, need further assessment.

How CA125 and ultrasound work together

Neither test is perfect on its own, so specialists look at them together, along with your age, symptoms and whether you have gone through the menopause. The CA125 level and scan findings can be combined into a risk score to help decide what happens next. NICE guidance on ovarian cancer sets out how GPs should use these tests when symptoms suggest ovarian cancer.

If the overall picture is reassuring, you may simply be monitored or offered a repeat scan. If there is concern, you will be referred urgently to a gynaecology specialist, and further scans, such as CT or MRI, may follow. A diagnosis of ovarian cancer can only be confirmed by examining tissue, usually after a biopsy or surgery.

Know the symptoms

Because CA125 testing is not reliable enough to screen women without symptoms, being aware of the warning signs is important. See your GP if you have persistent bloating, pelvic or tummy pain, difficulty eating or feeling full quickly, or needing to pass urine more often, particularly if these happen on most days. Target Ovarian Cancer has helpful information on symptoms and support.

Waiting for test results can be an anxious time, and it is fine to ask questions at every stage. If you have been told you have a raised CA125 or an abnormal scan and would like specialist advice, please contact our team to arrange an appointment with Mr Abu.