Pelvic ultrasound for PCOD: what the scan shows and misses

The scan is often the part women remember most. Someone looks at a screen, goes quiet and says, "polycystic ovaries". Then the fear starts. So let us be calm and specific about what that phrase means.

What the scan looks at

A pelvic ultrasound uses sound waves to make a picture of your ovaries and your womb lining. Nothing is cut, no radiation is used, and it usually takes only a few minutes.

In PCOD the doctor checks two things. One is the ovaries, for many small fluid-filled sacs. The other is the womb lining, for how thick it is. Both tell a story that blood tests cannot.

What the dots are

Your ovaries store eggs inside tiny fluid-filled sacs called follicles. In a typical month one follicle grows, matures and releases an egg. In PCOD many follicles start to grow but stall, so the egg is not released on time.

On a scan, those stalled follicles show up as a ring of small dots. They are not harmful cysts. They do not turn into cancer, and they usually do not need surgery. The word "cyst" in the old name is what made so many women worry.

What the scan cannot tell you

A scan is a picture, and a picture has limits.

First, it is only one of three signs in the Rotterdam criteria. A diagnosis needs any 2 of 3: irregular or no ovulation, high androgens, and polycystic ovaries on a scan. You can have PCOD with ordinary-looking ovaries, if the other two signs are there.

Second, the reverse also happens. Small follicles on a scan with regular periods, easy conception and no symptoms is called PCOM, which means polycystic ovarian morphology. It is a scan finding only, not a hormone problem. The usual plan is a short targeted diet, and your doctor decides what it means for you.

Third, the scan does not show how your hormones are behaving or how your body handles sugar. Those need blood tests.

Teenagers and the scan

For teens, a scan alone is not used to diagnose PCOD in the first 8 years after periods start. Young ovaries often look polycystic. Irregular periods are also common in the first 2 to 3 years, as the body settles in. So a doctor reads the scan with the history and tests, and may suggest waiting and watching. Parents can take some comfort here. A scan report with the word "polycystic" on it is not a diagnosis by itself.

Why the lining matters

The scan also measures the womb lining. When periods are missed for many months, the lining can keep thickening. Over the years this can cause heavy bleeding and, rarely, serious lining changes. A doctor can give a simple treatment to protect it. An ultrasound is the first way to check how thick the lining is. If something looks unusual, your doctor may advise further steps such as a biopsy or hysteroscopy, but only if needed.

What to expect on the day

• You may be asked to drink water and hold your bladder for a tummy scan. Follow the instructions you are given.
• The sonographer or doctor moves a handheld device over your lower tummy with some gel.
• Sometimes a slim probe is used inside the vagina, which gives a closer view. If you have never had a scan like that, or you are uncomfortable, tell the doctor. Ask which type is planned and why. The choice depends on your situation.
• Wear loose, easy clothes. Bring a parent or friend if you want one in the room.
• Tell the doctor the date of your last period. It helps to read the scan.

You will usually get the report the same day or soon after. Do not read it alone and panic. Bring it to your doctor, who reads it with your history and blood tests.

Where the scan fits

Think of three pieces of evidence. The calendar tells you about ovulation. Blood tests and your skin tell you about androgens. The scan shows the ovaries. Doctors need two of the three, once other conditions such as thyroid and prolactin problems are ruled out.

This article is education, not a diagnosis. A doctor decides what your scan means for you.