Diagnosing Endometriosis

How We Diagnose Endometriosis

Endometriosis sufferers often require multiple visits across multiple years before their condition is diagnosed. There are several reasons endometriosis is so poorly diagnosed, including:

  • Endometriosis has inconsistent symptoms between patients
  • Many of those symptoms are easy to mistake for symptoms of other conditions, such as irritable bowel syndrome
  • General Practitioners and OBGYNs are dismissive of female patient pain and patients themselves may downplay and normalize their cramps or pain with periods
  • We don’t have methods for diagnosis that are both accessible and reliable

    In this lesson we’ll focus on the last point, our methods for diagnosing endometriosis and the trade-offs of each, which we summarize below.

Summary Of Diagnostic Approaches For Endometriosis

Accuracy Of Tools For Diagnosing Endometriosis

Before we look at each form of diagnosis, we want to say a word about “accuracy.” Accuracy of a test can be broken down into two concepts: a test’s “positive predictive value” or PPV and its “negative predictive value” or NPV. We will refer to this constantly and so it’s worth committing to memory.

  • Positive predictive value (PPV): If the test says you’re positive, you actually do have the condition. For example, if a test indicates 100 people have endometriosis but we later find out that only 99 truly have it, the test has a 99% PPV.

  • Negative predictive value (NPV): If the test says you’re negative, you truly are. For example: a test says 100 patients don’t have endometriosis, but in reality 97 of those patients truly don’t have it (thus 3 patients actually do), the test as a 97% NPV.

Testing Accuracy Principals

For each of the major diagnostic modalities, we break down their level of accuracy in diagnosing endometriosis depending on where the endometriosis may reside.

Accuracy of Endometriosis Diagnostic Tests

Surgery As A Diagnostic

Patients can undergo surgery during which cameras or scopes are used by a gynecologist or reproductive endocrinologist to make a diagnosis of endometriosis. Surgery is technically considered the only way to definitively diagnose endometriosis and is considered “the gold standard,” but in current practice this is more a means for standardizing patients in research studies and many patients are presumably diagnosed and treated without a surgical diagnosis.

Strengths & Weaknesses of surgery as a diagnostic for endometriosis

During surgery, endometriosis can be diagnosed two ways:

  1. Visual inspection: The surgeons sees lesions (spots of inflammation) that are consistent with endometriosis and diagnoses the patient as having it.
  2. Biopsy: The doctors takes biopsies, small samples of cells, that are later inspected under a microscope to see if the cells in the biopsy have endometriosis.

Surgery has a number of crucial benefits but also real drawbacks. For that reason, many doctors and societies recommend against it when used solely for the purpose of diagnosis.

Benefits of Diagnostic Surgery

Surgery as a diagnostic has five major benefits: it’s accurate, allows the doctor to treat the disease in that moment, allows the doctor to double check whether the fallopian tubes are truly open or closed, and helps the doctor characterize how widespread the disease has become.

Strong Accuracy: Surgery’s chief benefit is that it’s more accurate in diagnosing endometriosis than any other method we have. When the diagnosis is made by:

  • Biopsy: The “theoretical” Positive Predictive Value (says I have it & I do) and Negative Predictive Value (says I don’t have it and I don’t) are very close to 100% because it is the most advanced tool we have for diagnosing patients. There is no more advanced test to tell us if a biopsy diagnosis is wrong.

  • Visual: When a doctor says a patient has endometriosis upon visual inspection, only 50 - 80% of the cases does the patient actually have it (when compared to a biopsy that is later evaluated under the microscope.) This means visual inspection has an approximate Positive Predictive Value (says I have it & I do) of 50 - 80%, with a greater PPV in more advanced stages of endometriosis. Said differently, in 20 - 50% of cases, if a patient was diagnosed by surgical visual inspection alone as having endometriosis, the diagnosis is incorrect.

Among patients with symptoms, when the doctor does surgery and visually determines there is no endometriosis, in 6% of cases they are wrong and a biopsy reveals the patients actually do have endometriosis. This means visual inspection has a 94% Negative Predictive Value (says I don’t have it and I really don’t).

Accuracy of diagnostic surgery for endometriosis

Ability To Treat At The Same Time: During diagnostic surgery, some clinicians can also treat (remove or destroy) the areas of endometriosis. As we’ll discuss in the next lesson, this has value for reducing pain, but may not necessarily improve pregnancy rates.

Ability To Inspect Fallopian Tubes: During diagnostic surgery, doctors can also inspect the fallopian tubes to determine whether they are open. Open tubes are a requirement for the sperm and egg to meet and for natural conception or intrauterine insemination (IUI), to work.

Surgical inspection is more accurate than other methods to look at the tubes like HSG or FemVue ultrasound. For instance, in 23% of cases an HSG says a woman’s tubes are closed when they are actually open. The implication is that for some patients who are told they must do IVF on account of their closed tubes, the option to conceive naturally, or through IUI, may still exist. For women who have been told they have a tubal blockage, visual inspection can be a valuable benefit of diagnostic surgery for endometriosis.

Accuracy of HSG in diagnosing open or closed fallopian tubes

Ability To “Stage” Endometriosis: During surgery a doctor can get a sense for how widespread the endometriosis is. This often correlates into a “staging system.” The most popular staging system is the ASRM system whereby doctors rank the endometriosis on a 1 - 4 scale (4 being the most widespread).

The ASRM staging system is useful in that it can help your doctor know what research is relevant to your case and maybe the next logical step for treatment. In this regard, being able to “stage” your case is useful.

However, ASRM staging system has poor reproducibility (50% of the time doctors disagree on the stage) and has virtually no predictive value of a patient’s likelihood to conceive.

The one staging system we believe can credibly predict outcomes post-surgery is known as the Endometrial Fertility Index (EFI). We’ll address it in the next lesson where we discuss the likelihood of success by each treatment option (like surgery or IVF).

Diagnosis And Removal Of Other Abnormalities: During surgery other abnormalities can be found and can possibly be treated, namely, in very rare circumstances, ovarian cancer.

Negatives Of Diagnostic Surgery

Surgery as a diagnostic has many drawbacks and for that reason many recommend against using it purely to make a diagnosis. Here are the reasons why:

  • Risk To Egg Supply: During surgical diagnosis if the doctor decides to treat (burn or cut) endometriosis on the ovary, this can impair a woman’s egg supply, reducing ovarian reserve and hurting her ability to conceive

  • Risk of Complications: Roughly 1% of patients suffer issues related to the surgery or anesthesia

  • Patient Inconvenience: Nearly all patients face a recovery time of 2 to 6 weeks, which can force them to miss work or the ability to handle other responsibilities

Given this, the American Society of Reproductive Medicine recommends against using surgery solely to make a diagnosis of endometriosis in patients who don’t have symptoms. However, it may be necessary if another diagnosis needs to be excluded or if your physician thinks there may be benefit of surgically treating endometriosis.

When deciding whether surgery should be used to diagnose endometriosis, you should be aware of bias from your doctor’s background. A minimally invasive surgeon or gynecologist who performs surgery frequently is more likely to recommend surgery for diagnosis. On the other hand, a reproductive endocrinologist (who belongs to ASRM, the society that recommends against surgery for diagnostic purposes) specializes in assisted reproduction and may be less likely to perform surgery and more likely to recommend other treatments like IVF. Both perspectives can be correct depending on the situation, and while potentially confusing it can often be helpful to get a second opinion before choosing a particular treatment.

Diagnosing Endometriosis Using Symptoms And Physical Exam

Because surgery is invasive, many doctors will make a “presumptive diagnosis” of endometriosis based on a patient’s symptoms. There is a long list of potential symptoms caused by endometriosis — most of which can also be caused by other conditions — making diagnosis tricky. The most common symptoms that should raise your suspicion of endometriosis include:

Symptoms of Endometriosis

In conjunction with taking account of symptoms, a doctor will also perform a physical exam. During an exam, a doctor will place a duck-billed instrument called a speculum into the vagina to better visualize the cervix and vagina. Then with one hand placed on the lower abdomen and the other in the vagina, the doctor will try to palpate the uterus, ovaries, the ligaments that support the uterus, and any masses that may be present and appreciate any areas that are tender.

Occasionally, doctors will prescribe continuous birth control pills, progesterone, or lupron upon making a diagnosis based on symptoms. These drugs starve endometriosis (if it exists) of estrogen needed to grow. If the patient’s pain symptoms go away after birth control, the doctor will feel more confident in their initial presumptive endometriosis diagnosis. Of course, this will not be an option for women trying to conceive now.

Diagnosing Endometriosis With A Physical Exam - strengths and weaknesses


The accuracy of taking a history and doing a physical exam is mediocre and varies depending upon where the endometriosis may reside. Accuracy for endometriosis on the ovary is high because on a normal ovaries doctors can barely feel it in on physical exam. If a doctor can feel it, or it’s tender, it may well be enlarged by endometriomas (endometriosis-filled sacs on the ovary).

More problematic is that doctors doing a physical have a very low Positive Predictive Value (says I have it & I do) for endometriosis in other parts of the pelvis. In over half of the instances, when a doctors diagnoses endometriosis not on the ovary using a physical exam, the patient does not in fact have it.

Accuracy of Diagnosing Using Symptoms & Physical Exam

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In this course we cover the controversial, but important, topics of diagnosing endometriosis -- the accuracy and risks of the various options, and which makes sense for whom. We take a deep look at which treatments are best for different types of women with the goals of either treating infertility or endometriosis-related symptoms.