Endometriosis Workup

Updated: May 10, 2021
  • Author: G Willy Davila, MD; Chief Editor: Michel E Rivlin, MD  more...
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Approach Considerations

Few laboratory tests prove to be valuable in the diagnosis of endometriosis, although some tests may be helpful in ruling out specific conditions in the differential diagnosis.

Routine radiographs are not recommended unless other disease entities requiring these studies are in the differential diagnosis.

Pelvic ultrasonography, computed tomography (CT) scanning, and magnetic resonance imaging (MRI) are only useful in the case of advanced disease with endometrial cyst formation or severe anatomic distortion. Intravenous pyelography and colonic studies are indicated if the clinical presentation suggests extragenital involvement of these organ systems.

Gross visualization of endometrial implants remains the definitive method of diagnosis. In this era of minimally invasive surgery, laparoscopy is the procedure of choice. Laparotomy can be another method of diagnosis. This is usually performed when another cause of patient pain is suspected.

Hysterosalpingography may reveal tubal occlusion or periadnexal adhesions.

Conscious pain mapping (ie, with the patient awake) has been used to locate the specific areas that cause pain. [42] Subsequently, the patient is placed under anesthesia and the deposits are ablated.


Laboratory Studies

A complete blood cell (CBC) count with differential may help differentiate pelvic infection from endometriosis as well as assess the degree of blood loss.

Urinalysis and urine culture should be sent if urinary tract infection (UTI) is in the differential diagnosis. In addition, cervical Gram stain and cultures should be considered, because sexually transmitted diseases (STDs) can also cause pelvic pain and infertility.

With a serum cancer antigen 125 (CA-125) test, serial measurements have a low sensitivity in detecting endometriosis, [49] although levels may be elevated in advanced cases, but the results are useful as prognosticators of treatment outcome. [50] However, normal posttreatment values do not mean that endometriosis is absent. Thus, the test lacks adequate sensitivity or specificity to be of clinical value.

Outpatient tests

A diagnostic test based on the detection of autoantibodies against Thomsen-Friedenreich (T) antigen (Gal beta1-3GalNAc) bearing proteins appears promising. The sensitivity and specificity of the test are 80%. This test may prove useful in the outpatient setting. [51]

Another office test is the marker CCR1. The expression of the blood-borne marker CCR1 mRNA in peripheral blood leukocytes is significantly higher in women with endometriosis compared with unaffected women. [52]



Endometriosis can be assessed by either transvaginal ultrasonography or endorectal ultrasonography. The ultrasonographic features of endometriomas vary from simple cysts to complex cysts with internal echoes to solid masses, usually devoid of vascularity. [53]

Transvaginal ultrasonography is a useful method of identifying the classic chocolate cyst of the ovary. The typical appearance is that of a cyst containing low-level homogenous internal echoes consistent with old blood.


MRI and CT Scanning

Magnetic resonance imaging (MRI) offers a superior combination of 3-dimensional (3-D) imaging with high-resolution special and temporal resolution, low observer dependency, no radiation exposure, and none of the risks associated with iodinated contrast agents.

With dynamic contrast-enhanced MRI, dynamic changes in MR signal intensity in selected tissues can be detected. Some of the newer generation contrast agents can be loaded with specific antibodies that allow for targeted imaging.

MRI is helpful in detecting rectal involvement [54] and has been shown to accurately detect rectovaginal endometriosis and cul-de-sac obliteration in more than 90% of cases when ultrasonographic gel was inserted in the vagina and rectum. [55] MRI has a higher sensitivity for detecting pelvic masses than ultrasonography but is limited in identifying diffuse pelvic endometriosis.

However, the cost-effectiveness of this MRI for endometriosis has yet to be justified for use as a routine tool.

Using computed tomography (CT) scanning, endometriomas may appear as cystic masses, but their appearance is nonspecific and this imaging modality should not be relied on for diagnosis. Complications of endometriosis, including bowel obstruction and hydronephrosis, may be seen on CT scans.


Laparoscopy and Biopsy

Laparoscopy is considered the primary diagnostic modality for endometriosis. This is an invasive procedure with an overall sensitivity of 97% and a specificity of only 77%.

Endometriosis has been described as protean in appearance. The classic lesions are blue-black or have a powder-burned appearance (see the first 2 images). However, the lesions can be red, white, or nonpigmented. Peritoneal defects and adhesions are also indicative (see the second 2 images). Bear in mind that microscopic evidence of endometriosis may be found in normal-appearing peritoneum.

Powder-burn lesions of endometriosis. Powder-burn lesions of endometriosis.
Active endometriosis with red and powder-burn lesi Active endometriosis with red and powder-burn lesions and adhesions from old scarring.
Peritoneal erosions and adhesions in the posterior Peritoneal erosions and adhesions in the posterior cul-de-sac. These are typical of more severe endometriosis.
Adhesions due to endometriosis. Adhesions due to endometriosis.

The most common sites of involvement found during laparoscopy are the following, in descending order (see the following images):

  • Ovaries

  • Posterior cul-de-sac

  • Broad ligament

  • Uterosacral ligament

  • Rectosigmoid colon

  • Bladder

  • Distal ureter

The following images are from various sites of endometriosis involvement.

Endometriosis. Red lesions on various organs. Endometriosis. Red lesions on various organs.
Endometriosis. Red lesions on the sigmoid colon an Endometriosis. Red lesions on the sigmoid colon and cul-de-sac.
Peritoneal erosions and adhesions in the posterior Peritoneal erosions and adhesions in the posterior cul-de-sac. These are typical of more severe endometriosis.
Typical appearance of minimal endometriosis on the Typical appearance of minimal endometriosis on the uterosacral ligaments. Note that some are pigmented (contain hemosiderin), whereas others are not.

In a study of low-grade ovarian endometrial adenocarcinomas, KRAS mutations were identified in 29% of endometriosis-associated tumors but only 3% in which endometriosis was not identified. This may be relevant to future targeted therapies. [56]

Histologic features

Histologic demonstration of both endometrial glands and stroma in biopsy specimens obtained from outside the uterine cavity is required to make the diagnosis of endometriosis. Occasionally, the finding of fibrosis in combination with hemosiderin-laden macrophages is sufficient for a presumptive diagnosis.