Checking for endometriosis typically involves several steps, starting with a pelvic exam and imaging, and sometimes ending with surgery. There is no single quick test that confirms the diagnosis for everyone, which is one reason the average delay from first symptoms to diagnosis still ranges from 5 to 8 years depending on the country. Here’s what each step in the process actually looks like.
The Pelvic Exam
The first thing most doctors do is a physical and pelvic exam. During this exam, your doctor presses on specific areas of your pelvis to check for focal tenderness, which is pain that flares when pressure hits a particular spot. They’re also feeling for tissue that has hardened or thickened, sometimes described as a nut-like nodularity. That texture can indicate endometriosis has deeply infiltrated tissue outside the uterus.
Your doctor will also check whether your pelvic organs move freely. Endometriosis can cause scar tissue (adhesions) that essentially glues the uterus to nearby organs, making it immobile. A uterus that feels fixed in place or tilted backward, combined with tenderness and nodularity, raises suspicion. But a normal pelvic exam doesn’t rule endometriosis out, especially in early or mild cases where there’s nothing abnormal to feel.
Transvaginal Ultrasound
Transvaginal ultrasound (TVUS) is usually the first imaging test ordered. A small probe is inserted into the vagina to get close-up images of the uterus, ovaries, and surrounding structures. It’s particularly good at spotting endometriomas, the fluid-filled cysts that form on the ovaries. For endometriomas, TVUS has a sensitivity of about 93% and a specificity of 96%, meaning it catches the vast majority and rarely gives a false alarm.
When performed by a specialist trained in endometriosis imaging, TVUS can also detect deeper disease. For deep infiltrating endometriosis, sensitivity is roughly 79% to 88%, depending on the location. A technique called the “sliding sign” helps evaluate whether the uterus and bowel glide freely against each other. When they don’t, it suggests the pouch of Douglas (the space between the uterus and rectum) is partially or fully sealed off by scar tissue. This technique alone has an accuracy of about 93% for detecting that specific problem.
The key limitation: a standard ultrasound performed by someone without specialized training in endometriosis can easily miss disease that isn’t on the ovaries. If your ultrasound comes back “normal” but your symptoms are significant, that doesn’t necessarily mean you’re clear.
MRI for Deeper Disease
Pelvic MRI is often the next step when deep infiltrating endometriosis is suspected, particularly if surgery is being planned and the surgeon needs a detailed map of where disease has spread. MRI picks up deep endometriosis with a sensitivity around 94%, making it slightly better than ultrasound for this type. On MRI, deep endometriosis lesions typically appear as dark nodules on certain image sequences, reflecting the dense fibrous and muscular tissue that surrounds the misplaced endometrial glands.
MRI is especially useful for evaluating whether endometriosis has grown into the bowel wall, the bladder, or the ligaments behind the uterus. Bowel involvement is suspected when the rectal or colon wall looks thickened or nodular on imaging. One limitation is that MRI cannot always determine exactly how deep a nodule has penetrated into the bowel wall, which sometimes only becomes clear during surgery.
Laparoscopy: The Surgical Look
For years, laparoscopy was considered the only definitive way to confirm endometriosis. It remains the gold standard when imaging is inconclusive or when a doctor needs to both diagnose and treat in the same procedure. During laparoscopy, a surgeon makes one or more small incisions in your abdomen and inserts a thin tube with a camera (a laparoscope) to visually inspect the pelvic organs and surrounding tissue.
The surgeon looks for endometriosis implants, which can appear as dark spots, red or clear lesions, or white scar tissue on the surfaces of organs and the pelvic lining. When suspicious tissue is found, a biopsy is taken and sent to a pathologist for confirmation under a microscope. This histological confirmation is what separates a visual impression from a definitive diagnosis. In some cases, the surgeon can remove or destroy endometriosis lesions during the same procedure, turning a diagnostic surgery into a treatment.
A less common option is laparotomy, which uses one larger incision across the abdomen instead of several small ones. This is generally reserved for extensive disease that can’t be managed through the smaller openings.
Preparing for Diagnostic Surgery
If you’re scheduled for a laparoscopy, preparation typically starts the day before. You’ll need to stop eating and drinking after a specific time the night before, usually around 11:30 p.m., though clear liquids like water or apple juice are often allowed up to two hours before the procedure. An empty stomach reduces anesthesia risks.
You’ll be asked to shower with an antibacterial body wash containing chlorhexidine (sold under brand names like Hibiclens) the evening before. All body piercings, jewelry, and nail polish need to be removed. If you wear acrylic nails, at least one nail on each hand must come off so the surgical team can monitor your oxygen levels through your fingernail during the procedure. If you tend toward constipation, your doctor may recommend a laxative beforehand to make sure your bowels are empty, since a full bowel can obstruct the surgeon’s view.
How Endometriosis Is Staged
When endometriosis is confirmed surgically, it’s classified into one of four stages using a point-based system. Points are assigned based on the size and location of lesions on the peritoneum and ovaries, the extent of adhesions on the ovaries and fallopian tubes, and whether the space behind the uterus is partially or completely sealed off. The points are totaled:
- Stage 1 (Minimal): 1 to 5 points
- Stage 2 (Mild): 6 to 15 points
- Stage 3 (Moderate): 16 to 40 points
- Stage 4 (Severe): more than 40 points
One important thing to know: staging reflects the physical extent of the disease, not how much pain you experience. Someone with Stage 1 can have debilitating symptoms, while someone with Stage 4 may have relatively mild pain. The staging is most useful for surgical planning and fertility assessments, not for predicting your day-to-day experience.
A Saliva Test on the Horizon
One of the biggest developments in endometriosis diagnosis is a saliva-based test that measures small molecules called microRNAs. In a multicenter clinical study of 971 symptomatic women across 17 hospitals in France, published in NEJM Evidence, the test demonstrated 97.3% sensitivity, 94.1% specificity, and an overall accuracy of 96.6%. Those numbers rival surgical diagnosis, and the test requires nothing more than a saliva sample.
This test is not yet widely available, but it represents a potential shift away from the years-long diagnostic journey many patients currently face. If validated in broader populations and approved by regulatory agencies in more countries, it could dramatically shorten the gap between first symptoms and a confirmed diagnosis.
Why Diagnosis Takes So Long
The average delay from the onset of symptoms to a confirmed endometriosis diagnosis is between 5 and 8 years, and research shows this timeline has not improved much over the past two decades. Several factors contribute. Symptoms like painful periods, pelvic pain, and pain during sex overlap with many other conditions. Mild or superficial endometriosis doesn’t always show up on imaging. And because a definitive diagnosis has traditionally required surgery, many doctors and patients reasonably try to manage symptoms with medication first, pushing back the timeline for a formal diagnosis.
If you’re in the process of being evaluated, knowing the full range of diagnostic tools available, from specialized ultrasound to MRI to laparoscopy, can help you have a more informed conversation with your doctor about which next step makes sense for your situation.