Occult microscopic endometriosis is a form of endometriosis that’s difficult for doctors to detect with standard diagnostic techniques. Symptoms include pelvic pain that worsens before or during your period.

Young woman with endometriosis.Share on Pinterest
Getty Images/Delmaine Donson

Occult microscopic endometriosis happens when tiny patches of endometrial tissue grow in areas outside the uterus. Unlike standard endometriosis, which doctors can see when they look inside your pelvis, occult microscopic endometriosis is very difficult to detect.

In medicine, “occult” means “hidden.”

This article discusses occult microscopic endometriosis, its symptoms, how doctors diagnose it, and its treatment options.

Occult microscopic endometriosis happens when tiny, microscopic patches of endometrial tissue grow outside the uterus. These patches aren’t visible during typical diagnostic procedures.

Research on microscopic endometriosis is limited. Some research has shown the presence of microscopic endometrial lesions in tissue samples.

These tiny lesions can be present in people with visible endometriosis and those with no visible symptoms of the condition.

Occult microscopic endometriosis might cause symptoms similar to typical endometriosis, but research is too limited to know for sure.

People with no symptoms of endometriosis can have tissue samples that test positive for microscopic endometriosis. This means it’s possible that symptoms like pelvic pain and severe period cramps could be unrelated to these microscopic lesions.

But in one study from 2013, women with visible endometriosis were more likely to also have occult microscopic endometriosis in the pelvic cavity than women without the condition.

A 2020 study looked at the occurrence of occult microscopic endometriosis in 142 people with chronic pelvic pain and no visible endometriosis in the peritoneum during laparoscopy. The study found that about 39% had occult microscopic endometriosis.

This could indicate that occult microscopic endometriosis causes chronic pelvic pain. This pain may be ongoing or worsen before or during your periods.

Some people may also experience other symptoms typical of endometriosis, such as:

The gold-standard diagnostic protocol for endometriosis is laparoscopy, with confirmation from tissue analysis. During a laparoscopy, your doctor uses an instrument called a laparoscope to look at your abdominal cavity, pelvis, organs, and peritoneum.

Surgeons typically take tissue samples from areas where they see endometrial lesions. If you have occult microscopic endometriosis in other areas, it’s difficult for your surgeon to determine which tissue to sample.

More thorough testing for microscopic endometriosis could include random tissue sampling of your pelvic cavity. It may also include advanced laparoscopic techniques that allow for better visualization of endometrial lesions. These techniques, which may be unavailable today, could include:

  • 5-aminolevulinic acid-induced fluorescence
  • autofluorescence imaging
  • narrow-band imaging
  • indocyanine green near-infrared imaging
  • 3D laparoscopy

Your doctor may recommend treatment if they believe occult microscopic endometriosis is causing your pain or other symptoms.

Hormone therapy

Hormone-regulating therapy can help slow the growth of endometrial lesions and prevent new ones from forming.

There are different types of hormone-regulating medications, including:

  • progestin
  • gonadotropin-releasing hormone agonists and antagonists
  • aromatase inhibitors
  • hormonal contraceptives

Surgical interventions

During a laparoscopy, surgeons can remove or destroy visible endometrial patches. This can help relieve the symptoms of endometriosis in some people.

The fact that endometriosis often comes back in the years following surgery suggests that some cells may be left behind.

Depending on the location of your endometriosis, surgical procedures could include:

  • excision or ablation during laparoscopy
  • hysterectomy
  • bowel resection
  • resection of scar tissue

Pain management

If you experience severe symptoms like pain, your doctor may prescribe medications such as ibuprofen and naproxen sodium to help ease them.

Here are some common questions about occult microscopic endometriosis:

Can you have regular endometriosis and occult microscopic endometriosis?

It’s possible to have regular endometriosis and occult microscopic endometriosis. There might be a slightly higher occurrence of occult microscopic endometriosis in people with visible endometriosis than in those without it.

Can occult microscopic endometriosis affect fertility?

There’s no evidence that occult microscopic endometriosis has any effect on fertility. But, regular, visible endometriosis can contribute to infertility.

Can occult microscopic endometriosis cause endometriosis to recur after surgery?

Researchers believe microscopic endometrial lesions are biologically active and can retain their growth potential, possibly leading to the recurrence of endometriosis after surgery.

  • Occult microscopic endometriosis means endometriosis that isn’t visible with standard diagnostic techniques like laparoscopy.
  • Research into occult microscopic endometriosis is limited, but people with and without visible endometriosis have reported cases of it.
  • Growths that are more difficult to see are also harder to test for and treat.