Diagnosing endometriosis

This article was medically reviewed by Andrew Horne, Professor of Gynaecology and Reproductive Sciences at Edinburgh University's MRC Centre for Reproductive Health.

There are two ways to diagnose endometriosis: a suspected (clinical) diagnosis, which is based off symptoms or imaging tests, and a surgical diagnosis, which is the definitive way to confirm endometriosis. This is done through laparoscopy, also known as keyhole surgery. There is no blood test, procedure, or imaging test that can be done to confirm endometriosis without surgery.  

However, the path to getting a diagnosis is not always simple. Many sufferers have to attend a number of GP and gynaecological appointments and undergo different tests to get an accurate diagnosis. There are a few reasons for this. First, endometriosis has a wide range of symptoms that can also be found in other gynaecological and non-gynaecological conditions. This means endometriosis can be misdiagnosed or confused for another condition. Second, endometriosis can affect people differently, so not every person will experience the same symptoms. Finally, lack of medical research and education around endometriosis can increase the delay in diagnosis. 

In your first appointment your GP will begin with asking for your symptoms. The NICE guidelines recommend that physicians (GP or gynaecologist) look for cyclical and repetitive symptoms that the patient experiences both, during and outside of their period.  

The symptoms for endometriosis that are recognised by the NHS include: 

• Irregular spotting or bleeding heavier than usual for longer times.
• Period pain becomes more severe and prevents you from engaging in day-to-day activities.  
• Pain or bleeding when urinating, passing bowels, or having sex.  
• Over-the-counter pain medications like paracetamol or ibuprofen are not enough to relieve your pain. 

You may have symptoms that are not included in this list, and you should still mention these to your physician. Your GP may suspect that you have endometriosis or a different gynaecological or non-gynaecological condition at this point. They can refer you to another GP for a second opinion or a gynaecologist to perform more specialty tests.  

Physical tests 

After hearing your symptoms, your GP can perform a physical examination. This may be an abdomen or a pelvic (vaginal) exam.  

• In an abdominal exam, the physician will touch your stomach to observe any tender or sore areas and apply pressure to different abdominal areas to feel the presence of any masses. An abdominal exam is performed before the pelvic exam.   
• In a pelvic exam, also known as vaginal exam, the physician will keep one hand on your tummy and use their fingers to examine your vaginal cavity. The physician will feel for any scars or masses in your vagina and cervix which might indicate inflammation. If the abdominal and pelvic exams are normal and the patient still expresses symptoms, the NICE guidelines recommend moving to the next stage, which is starting a treatment plan. Your GP may refer you for imaging tests to continue the investigation.

Imaging tests 

MRI, transvaginal or transrectal ultrasounds are non-invasive imaging tests that your gynaecologist can perform if they suspect endometriosis. They are visual techniques that allow the physician to map out the uterus and study the extent of the disease.

It is particularly useful when the patient has lesions that are embedded deep into the tissue (deep endometriosis) or large inflamed tissue on the ovaries (endometriomas). If the lesions are small and only on the surface of the tissue (superficial peritoneal endometriosis), it may not be possible to see it with an ultrasound.  

A gynaecologist or a specialist in ultrasounds (sonographer) will perform the exam. They will share the results with an experienced radiologist, who will write a report that communicates the findings with your gynaecologist.

• A transrectal ultrasound will show endometrial tissue near the back of the bladder, and a transvaginal ultrasound will show the ovaries, bladder, intestines and ovaries. The latter is the more common procedure, where the specialist will insert a lubricated wand-like device inside your vagina to record the shapes and structures of your uterus.   

Imaging tests cannot be used to confirm that patients have endometriosis because although the tissue can be clearly inflamed and damaged, the physician cannot be 100% sure it is endometrial tissue. Also, patients can have symptoms of endometriosis but have normal imaging results. To get a full confirmation, this requires surgery and a biopsy. However, imaging techniques are beneficial because it can help rule out other conditions and help your physician make next steps that get you closer to a correct diagnosis.  

Laparoscopic surgery 

In the NHS, the gold standard for diagnosing endometriosis is through laparoscopic surgery. It is also known as keyhole surgery since two to four small cuts are made near your belly button.

A laparoscope is inserted, which is a small rod that has a camera attached at the end. The laparoscope is connected to a television monitor which allows your physician to visualise the inside of your uterus. They can use either ablation or excision methods to remove the lesion. Ablation will just destroy the lesion at the top-most level, whereas excision will cut out the lesion with its surrounding damaged tissue and a small portion of health tissue as well. Based on the number and depth of the lesions, your surgeon will perform one of the techniques or a combination.  

Following this procedure, you may be diagnosed with one of three types of endometriosis:

• superficial peritoneal endometriosis (most common)
• endometriomas (cysts found on ovaries)
• deep endometriosis (lesions found outside of uterus).

Laparoscopic surgery can also treat your symptoms since the physician will remove the lesions causing pain. However, there is little scientific evidence to show that surgical treatment of superficial peritoneal endometriosis provides more symptom relief than treating the patient with hormone or pain therapy.   

Endometriosis stages

You may hear from your gynaecologist that you have Stage 1, 2, 3 or 4. This does not correspond with the severity of symptoms and only is used as an indicator of the number and depth of lesions present. This means that someone can have Stage 4 endometriosis and experience mild symptoms, compared to a person with Stage 1 endometriosis who experiences severe pain.   

A biopsy can be performed, where the lesions are removed by excision and sent to a histology laboratory to be studied under a microscope.  

It is recommended that gynaecologists treat patients based on their symptoms, preferences, and priorities, and not on the stage of endometriosis. However, it is important to note that laparoscopic surgery does not ‘cure’ endometriosis, and lesions may regrow leading to a return in symptoms. In this case, follow-up surgeries may be needed. 

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