Endometriosis is diagnosed through a combination of imaging and, in many cases, surgery. No single blood test can confirm it, and the disease often looks different from person to person, which is a major reason people wait between 4 and 11 years on average from symptom onset to diagnosis. Understanding how each diagnostic method works, what it can and can’t detect, and what the experience feels like as a patient can help you push for answers faster.
What Endometriosis Looks Like
Endometriosis tissue grows outside the uterus and takes on a surprisingly wide range of appearances, which is one reason it gets missed. Lesions can show up as pink or red spots (considered active, early-stage disease), dark blue-black patches sometimes described as “powder burns” or “mulberry-like” (a sign of more advanced disease that has bled into itself repeatedly), or white scarred areas. Some lesions look like tiny clear or brown blisters. Others appear as adhesive strands, yellowish patches, deep nodules, or even small pockets in the tissue lining the pelvis.
A classic endometriosis lesion has a ring of white scar tissue surrounding it. But many lesions lack that hallmark. The sheer variety of appearances means that a surgeon or radiologist needs specific training in recognizing all the forms the disease can take, not just the textbook black spots.
Transvaginal Ultrasound
A transvaginal ultrasound is typically the first imaging tool used. A probe is inserted into the vagina to get close-up views of the uterus, ovaries, and surrounding structures. Standard ultrasound picks up ovarian cysts caused by endometriosis (endometriomas) and signs of adenomyosis, a related condition where tissue grows into the uterine wall. But with specialized technique, it can do much more.
The International Deep Endometriosis Analysis group developed a four-step ultrasound protocol that goes well beyond a routine scan. It includes evaluating the uterus and ovaries for cysts, intentionally searching for deep endometriosis in the front and back compartments of the pelvis, performing dynamic maneuvers (like the “sliding sign,” where the sonographer gently presses to see whether pelvic organs glide freely or are stuck together by adhesions), and using probe pressure to locate tender nodules and check ovarian mobility.
For deep endometriosis affecting the bowel, transvaginal ultrasound performed by experienced operators detects about 85 to 89% of lesions, with specificity around 96 to 97%, meaning false positives are rare. Its main limitation is detecting disease in harder-to-reach locations like the vaginal walls (around 55% sensitivity) or the ligaments behind the uterus (around 67 to 74% sensitivity). Overall pelvic sensitivity sits around 78%.
MRI for Deeper Disease
MRI provides a broader view of the pelvis and is particularly useful for mapping deep infiltrating endometriosis before surgery. It picks up about 91% of pelvic endometriosis overall and is stronger than ultrasound at detecting disease in the ligaments behind the uterus (94% sensitivity) and the vaginal walls (73% sensitivity). For bowel involvement, MRI and ultrasound perform similarly, both catching around 85 to 86% of lesions.
On MRI, endometriosis appears as dark areas on certain scan sequences, reflecting the fibrosis (scar tissue) that forms around misplaced endometrial tissue. Ovarian endometriomas show a characteristic pattern: they light up bright on one type of image due to blood products inside, then darken on another type, a phenomenon called “shading” that reflects chronic repeated bleeding with high concentrations of iron and protein within the cyst.
Preparation for a pelvic MRI is straightforward. You’ll fast for about four hours beforehand and change into a hospital gown. Some facilities use a small amount of gel inserted vaginally or rectally to improve image quality, but this isn’t always required. The scan itself typically takes 30 to 45 minutes.
Laparoscopy: The Surgical Approach
Laparoscopy has long been considered the gold standard for confirming endometriosis because it allows a surgeon to directly see and biopsy lesions. It’s a minimally invasive procedure done under general anesthesia, using a small camera inserted through a 5-millimeter incision at the navel.
A thorough diagnostic laparoscopy follows a systematic survey of the entire abdomen, not just the pelvis. The surgeon first checks the upper abdomen: the liver edge, gallbladder area, and diaphragm, since endometriosis can appear in unexpected locations. Next comes the lateral abdomen, looking for adhesions along the sides. Then the pelvic survey begins, typically moving in a counterclockwise pattern through the round ligaments, the space between the bladder and uterus, the ovaries and fallopian tubes, the pelvic sidewalls, and the area behind the uterus.
In many cases, the surgeon will also open the tissue layer covering the pelvic sidewall (the retroperitoneum) to inspect underneath, carefully identifying the ureters and blood vessels before peeling away the tissue to look for hidden lesions. This step is important because endometriosis can grow beneath the surface where it’s invisible from above. When lesions are found, they can often be removed during the same procedure rather than requiring a second surgery.
Recovery After Diagnostic Laparoscopy
A diagnostic laparoscopy is usually a same-day procedure. You go home within hours of waking up. The day after surgery, short walks of 10 to 15 minutes are encouraged, and by mid-week most people can walk for 30 to 60 minutes. You can shower and remove dressings after 24 hours. Swimming is fine as soon as it feels comfortable.
Most people return to work within one week, though the first 48 hours should be kept light. There are no strict lifting restrictions, but physically demanding jobs may leave you more fatigued initially. You shouldn’t drive for at least 24 hours after general anesthesia, and only when you can comfortably wear a seatbelt and perform an emergency stop.
How Imaging Compares to Surgery
Neither ultrasound nor MRI can detect superficial peritoneal endometriosis, the thin, scattered lesions that sit on the surface of the pelvic lining. These are only visible during surgery. For that reason, normal imaging does not rule out endometriosis. If your ultrasound and MRI come back clean but your symptoms strongly suggest the disease, laparoscopy remains the next step.
Where imaging excels is in mapping deep disease before surgery. Knowing the exact location and size of nodules affecting the bowel, bladder, or ureters lets surgeons plan the right team and approach. In many cases, a skilled ultrasound is enough for that mapping. MRI adds value when ultrasound findings are unclear or when disease is suspected in areas ultrasound struggles to reach.
Saliva Testing: A New Option
A saliva-based diagnostic test called Endotest became available within a clinical trial framework in France in February 2025. It works by analyzing a signature of small RNA molecules in saliva. In a study of 971 patients across 17 French centers, the test achieved 96.6% overall accuracy, with 97.3% sensitivity and 94.1% specificity. Among patients whose diagnosis was later confirmed surgically, the saliva test misclassified only 4.6% of cases, compared to 27.2% misclassification with imaging alone.
The test’s performance held steady regardless of patient age, disease stage, hormonal medication use, or how long the saliva sample spent in transit before analysis. If validated and approved more broadly, this type of test could dramatically shorten the years-long diagnostic delay that most people with endometriosis experience, offering a reliable answer without surgery or advanced imaging.
How Endometriosis Is Staged
Once endometriosis is confirmed, it’s typically classified using the revised American Society for Reproductive Medicine (rASRM) system, which assigns a point score based on the size and location of lesions and the severity of adhesions. Stage I (1 to 5 points) is minimal disease, Stage II (6 to 15) is mild, Stage III (16 to 30) is moderate, and Stage IV (31 to 54) is severe. A single finding of complete obliteration of the space behind the uterus scores 40 points on its own, automatically placing someone in Stage IV.
Staging doesn’t always correlate with pain. Someone with Stage I can have debilitating symptoms, while Stage IV may occasionally be discovered incidentally. The staging system is most useful for surgical planning and fertility discussions rather than predicting how the disease feels day to day.