Diagnosing endometriosis can be difficult, and there is often a significant delay between the onset of symptoms and diagnosis (Husby 2003; Kennedy 2005). Endometriosis may be initially suspected based on signs and symptoms and medical history (Ballard 2008; Laufer 2003), but a physical examination should also be performed (Laufer 2003). Pelvic tenderness and enlarged ovaries are suggestive of endometriosis (Kennedy 2005). In many cases, endometriosis is a diagnosis of exclusion, meaning doctors may come to the diagnosis once other causes of pelvic pain or infertility have been ruled out (Elsevier 2011).
The gold standard for diagnosing endometriosis is visual inspection via laparoscopy (Kennedy 2005; Schenken 2013; Winkel 2003). Laparoscopy is a surgical procedure that allows surgeons to look for ectopic endometrial tissue, which typically appear as black, dark-brown, or blue lesions that may resemble a powder burn (lesion sometimes seen after the skin is near the ignition of gunpowder). These lesions can be visually seen on the ovaries, peritoneum, and/or other structures within the pelvis. Laparoscopy can also help determine the extent of endometriosis (Schenken 2013; Kennedy 2005). Accuracy of this procedure depends heavily on the location of the lesions, extent of endometriosis, and experience of the person performing the procedure. There can be error when relying on laparoscopy findings alone to diagnose endometriosis (Wykes 2004; Schenken 2013; Winkel 2003). Ideally, suspicious lesions seen on laparoscopy should be sampled by performing a biopsy, thus allowing for microscopic confirmation of ectopic endometrial tissue (Schenken 2013; Kennedy 2005; Mounsey 2006). Although laparoscopy is the gold-standard technique for diagnosis, it is an invasive procedure. As a result, many doctors will first treat a woman suspected of having endometriosis with hormonal therapy before resorting to laparoscopy (Hsu 2010). Imaging studies, such as transvaginal ultrasound, can also help detect severe disease and may be useful as a test before laparoscopy (Holland 2010; Abrao 2007).
Laparoscopy also helps classify the severity of endometriosis into four stages: minimal, mild, moderate, and severe. Minimal endometriosis causes only isolated implants of ectopic endometrial tissue with no adhesions. Mild endometriosis is characterized by the presence of endometriotic implants on the peritoneum and ovaries cumulatively totaling less than 5 cm in size; no significant adhesions are present at this stage. In moderate endometriosis, multiple implants are present, including some that deeply penetrate the pelvic tissue and can cause significant adhesions (Schenken 2013; ASRM 2012). Women with severe disease have many deep implants and may have large masses called endometriomas (Schenken 2013).