A physician, often a gynecologist (GYN), will begin by taking a complete medical history and perform a physical examination, including a pelvic examination, to diagnose endometriosis. During the pelvic exam, the GYN may be able to detect masses on the ovaries or uterus. These may be endometrial cysts or implants, or may be related to other conditions. Physicians may also determine that a patient experiences pain when pelvic organs are moved. This can occur when there are a number of adhesions. In some cases, the uterus may become tilted back because of adhesions from the implants. Endometriosis can only be diagnosed by seeing the implants, which requires a surgical procedure, usually laparoscopy.

During this procedure, an incision is made in the abdomen and a small lighted viewing device is inserted into the pelvis. The surgeon can look for endometrial implants and possibly remove them at the same time by excising (cutting) them or burning them off with a laser or cautery (a heating device). Laparoscopy is the more common and less invasive method of diagnosis. An open abdominal surgery called a laparotomy may also diagnose endometriosis, but is less common in the United States. Surgeons can also remove lesions during a diagnostic laparotomy.

After laparoscopy, the physician can determine the stage of endometriosis. A system designed by the American Society for Reproductive Medicine (ASRM) helps classify the severity of the condition. However, the stages may not correspond to a woman’s level of pain. The stages are:

• Stage I. Minimal lesions. Isolated superficial implants.
  
  
• Stage II. Mild lesions. Several small implants and a few adhesions.
  
  
• Stage III. Moderate lesions. Superficial and deep implants with prominent adhesions.
  
  
• Stage IV. Severe lesions. Multiple superficial and deep implants, large endometriomas and prominent adhesions.

In addition, imaging tests may be used to rule out conditions that share similar symptoms. These tests can indicate severe cases of endometriosis, but do not provide a definitive diagnosis. For instance, imaging studies (e.g., ultrasound, CAT scan, MRI) of the pelvic region can identify certain endometrial implants or cysts, but not all.