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Diagnosis and investigation

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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In UK, a definite diagnosis of endometriosis is made around twelve years after the onset of symptoms due to overlapping symptoms of other gynaecological conditions (1).

  • laparoscopic visualisation is considered the gold standard investigation, unless visible lesions are seen in the posterior vaginal fornix or elsewhere (1,2,3)
  • changes suggestive of endometriosis may sometimes be seen on ultrasound scan
    • ultrasound (1):
      • transvaginal ultrasonography (TVS)
        • helpful in assessing endometriotic ovarian cysts.
        • TVS is of little value in assessing the presence of adhesions and mild peritoneal deposits
        • TVS may be useful in assessing deep infiltrating disease, where endometriosis involves the Pouch of Douglas
          • often hypoechoic linear thickening, or nodules/masses with or without regular contours can be seen on TVS
      • endoanal ultrasound
        • has been evaluated for the diagnosis of deep infiltrating endometriosis
      • if a transvaginal scan is not appropriate, consider a transabdominal ultrasound scan of the pelvis (3)

    • during a diagnostic laparoscopy, consider taking a biopsy of suspected endometriosis (3):
      • to confirm the diagnosis of endometriosis (be aware that a negative histological result does not exclude endometriosis)
      • to exclude malignancy if an endometrioma is treated but not excised
  • investigation of other possible sites is dictated by symptoms e.g. cystoscopy if bladder involvment is suspected

Do not exclude the possibility of endometriosis if the abdominal or pelvic examination, ultrasound or MRI are normal. If clinical suspicion remains or symptoms persist, consider referral for further assessment and investigation (3)

Notes (3):

  • Serum CA125
    • do not use serum CA125 to diagnose endometriosis
    • if a coincidentally reported serum CA125 level is available, be aware that:
      • a raised serum CA125 (that is, 35 IU/ml or more) may be consistent with having endometriosis
      • endometriosis may be present despite a normal serum CA125 (less than 35 IU/ml)
  • MRI
    • do not use pelvic MRI as the primary investigation to diagnose endometriosis in women with symptoms or signs suggestive of endometriosis
    • consider pelvic MRI to assess the extent of deep endometriosis involving the bowel, bladder or ureter
    • ensure that pelvic MRI scans are interpreted by a healthcare professional with specialist expertise in gynaecological imaging


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