Diagnosing Endometriosis

Clinical Diagnosis Framework

The American College of Radiology recommends transvaginal ultrasound (TVUS) as the initial imaging modality for suspected endometriosis, with expanded protocol TVUS plus transabdominal ultrasound or MRI pelvis being equally appropriate first-line options 1, 2, 3
The diagnosis of endometriosis is fundamentally clinical and does not require surgical confirmation before initiating empiric treatment, with imaging playing a critical role in treatment planning, reducing surgical morbidity, and preventing incomplete surgeries 1, 2

Key Clinical Features to Identify

Pain patterns, such as dysmenorrhea, dyspareunia, dyschezia, dysuria, or chronic pelvic pain, are associated with endometriosis 1, 2
Infertility is present in approximately 50% of patients with endometriosis 1, 2
Physical examination findings, such as nodularity, fixed retroverted uterus, or tender uterosacral ligaments, may be present in patients with endometriosis 1, 2

Imaging Algorithm

Expanded protocol TVUS demonstrates excellent performance for deep endometriosis detection and is comparable to MRI 2, 4, 3
MRI without IV contrast is sufficient for detecting deep endometriosis, while MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies 3, 5
Transabdominal ultrasound can be added to widen the field of view for urinary tract and bowel involvement beyond the pelvis 3, 5

Critical Pitfalls to Avoid

Do not rely on standard TVUS alone for deep endometriosis—expanded protocols or MRI are needed 1, 2, 3
Do not use CT pelvis as initial imaging—it has no role in standard endometriosis diagnosis 4, 3, 5
Do not assume negative imaging excludes endometriosis—superficial peritoneal disease is poorly detected by all imaging modalities 5

Diagnostic Delay Considerations

The current imaging-first approach reduces morbidity by enabling better surgical planning and decreasing incomplete surgeries requiring reoperation 1, 2

Diagnostic Approaches for Endometriosis

Imaging Modalities

Transvaginal ultrasound (TVUS) is recommended as the initial imaging modality for evaluating suspected endometriosis, with sensitivity of 82.5% and specificity of 84.6% 6
MRI should be considered if TVUS is inconclusive, particularly when coexisting pathologies like leiomyomas are present, as TVUS sensitivity drops to 33.3% in these cases 6
MRI has superior sensitivity (78%) and specificity (93%) for adenomyosis diagnosis when ultrasound findings are equivocal 6

Associated Risks and Considerations

Women with endometriosis are at higher risk for cardiovascular disease, including stroke (HR 1.34, 95% CI 1.10-1.62) 7
Endometriosis often coexists with adenomyosis, which requires different imaging approaches for diagnosis 6
Up to 44% of women experience symptom recurrence within one year after endometriosis treatment, requiring ongoing management 8
Endometriosis is associated with recurrent pregnancy loss and infertility, which may warrant pre-conception treatment 6

Biomarker Utility

In patients with extrauterine disease, serum CA-125 may be helpful in monitoring clinical response, but can be falsely elevated due to peritoneal inflammation/infection 9

Diagnosis and Management of Endometriosis

Laboratory Testing and Diagnosis

CA-125 has no clinical utility for diagnosis, and may be helpful for monitoring clinical response in patients with confirmed extrauterine disease, but can be falsely elevated due to peritoneal inflammation/infection, according to the American Society of Clinical Oncology 10
Identifying deep infiltrating disease that may require bowel or urologic surgery is crucial, and can be achieved through imaging, as recommended by the American College of Radiology 10

Associated Conditions and Risks

Women with endometriosis have an increased risk for stroke, with a hazard ratio of 1.34 and 95% confidence interval of 1.10-1.62, as reported by the American Heart Association [@2@]

Diagnosis and Management of Endometriosis
Laboratory Testing and Diagnosis
CA-125 has no clinical utility for diagnosis, and may be helpful for monitoring clinical response in patients with confirmed extrauterine disease, but can be falsely elevated due to peritoneal inflammation/infection, according to the American Society of Clinical Oncology 10
Identifying deep infiltrating disease that may require bowel or urologic surgery is crucial, and can be achieved through imaging, as recommended by the American College of Radiology 10

Diagnostic Criteria for Endometriosis

Clinical Diagnostic Framework

The American College of Radiology recommends that symptom patterns such as dysmenorrhea, dyspareunia, dyschezia, and dysuria establish a clinical diagnosis of endometriosis, with approximately 50% of cases presenting with infertility 11

Imaging Criteria

The American College of Radiology suggests that expanded protocol TVUS requires specialized training and evaluation of uterosacral ligaments, assessment of anterior rectosigmoid wall, dynamic sliding maneuvers, bowel preparation or enema, and evaluation of appendix and diaphragm 11, 12
The American College of Radiology recommends MRI pelvis without IV contrast for detecting deep endometriosis, with MRI diagnostic features including endometriomas, T2 dark spot sign, deep infiltrating endometriosis, and adhesions/cul-de-sac obliteration 13
The American College of Radiology reports that MRI performance by location includes 92.4% sensitivity and 94.6% specificity for intestinal endometriosis, 88% sensitivity and 83.3% specificity for deep infiltrating endometriosis, and 50% sensitivity and 97.3% specificity for bladder wall endometriosis 13
The American College of Radiology recommends moderate bladder distention and vaginal contrast to improve lesion conspicuity on MRI 11, 12

Surgical Diagnosis

The American College of Radiology states that laparoscopy with histologic confirmation is no longer required before initiating empiric treatment, and surgery is reserved for definitive treatment rather than diagnosis 11
The American College of Radiology suggests that preoperative imaging reduces morbidity and mortality by decreasing incomplete surgeries requiring reoperation, and imaging helps inform patient decision-making, surgical planning, and management 11

Diagnostic Approach for Suspected Endometriosis

Introduction to Diagnostic Challenges

The pouch of Douglas may contain a small to moderate amount of fluid in healthy women depending on their point in the menstrual cycle, as noted by the American College of Emergency Physicians 14
The pain associated with endometriosis has little relationship to the type of lesions seen at laparoscopy, though the depth of lesions does correlate with pain severity, according to the American Academy of Family Physicians 15

Diagnostic Imaging

MRI pelvis without IV contrast is the next step if TVUS is inconclusive or for surgical planning, with MRI showing 90.3% sensitivity and 91% specificity for deep pelvic endometriosis, as recommended by the American College of Radiology 16
MRI demonstrates key findings including T2 hypointense fibrosis at the torus uterinus and uterosacral ligaments, obliteration of the pouch of Douglas, and T1 hyperintense hemorrhagic foci, according to the American College of Radiology 17
MRI shows 90.3% sensitivity and 91% specificity for deep pelvic endometriosis, as reported by the American College of Radiology 17

Critical Considerations

Physiologic fluid in the pouch of Douglas is normal and does not necessarily indicate pathology, as noted by the American College of Emergency Physicians 14
CT pelvis has no role in standard endometriosis diagnosis, as stated by the American College of Radiology 16

Diagnostic Imaging for Endometriosis

Imaging Modalities and Techniques

The American College of Radiology recommends MRI pelvis without IV contrast if TVUS is inconclusive or for surgical planning, with a sensitivity of 90.3% and specificity of 91% for deep pelvic endometriosis 18
MRI performance by anatomic location shows 92.4% sensitivity and 94.6% specificity for intestinal endometriosis, and 88% sensitivity and 83.3% specificity for deep infiltrating endometriosis in posterior locations 19
Transrectal ultrasound can be useful for deep infiltrating endometriosis, with 97% sensitivity and 96% specificity for rectovaginal endometriosis, and 80% sensitivity and 97% specificity for uterosacral ligament implants 19
The American College of Radiology suggests that MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies, but IV contrast is not routinely needed for detecting deep endometriosis itself 18

Diagnostic Features and Technical Optimization

MRI diagnostic features for endometriosis include endometriomas, T2 dark spot sign, deep infiltrating endometriosis, and adhesions/cul-de-sac obliteration 19
Technical optimization for MRI includes moderate bladder distention and vaginal contrast to improve lesion conspicuity 19

Alternative Imaging Approaches

The American College of Radiology recommends using expanded protocol TVUS for suspected deep endometriosis, which includes evaluation of uterosacral ligaments, assessment of anterior rectosigmoid wall, dynamic sliding maneuvers, bowel preparation or enema, and evaluation of appendix and diaphragm 20

Diagnostic Imaging for Endometriosis

Recommended Imaging Protocols

The American College of Radiology recommends that MRI with IV contrast be used to differentiate endometriomas from ovarian malignancies, given the risk of endometriosis-associated malignancies, and technical optimization includes moderate bladder distention and vaginal contrast to improve lesion conspicuity involving these structures 21
MRI without IV contrast is sufficient for detecting deep endometriosis itself, but MRI with IV contrast is highly recommended for differentiation of endometriomas from ovarian malignancies 21
Expanded protocol TVUS requires specialized training and is not widely available in the United States, but shows significantly higher sensitivity for deep endometriosis and is comparable to MRI performance when performed by experts 21

Critical Pitfalls to Avoid

Do not use CT pelvis for initial imaging evaluation of suspected endometriosis, as there is no relevant literature supporting its use for this indication 21
Do not assume negative imaging excludes endometriosis, as all imaging modalities have poor sensitivity for superficial peritoneal disease 21
Preoperative imaging is associated with decreased morbidity and mortality by reducing incomplete surgeries that require repeat procedures, and accurate preoperative mapping of deep infiltrating disease is essential for optimal treatment planning 21

Diagnosing Endometriosis

Diagnostic Methods

Laparoscopy with histologic confirmation remains the gold standard for definitively diagnosing endometriosis, though current guidelines now support initiating empiric treatment based on clinical diagnosis alone without requiring surgical confirmation, as recommended by the American College of Obstetricians and Gynecologists 22
Only experienced surgeons familiar with the protean appearances of endometriosis should rely on visual inspection alone, otherwise, peritoneal biopsy should be used for questionable lesions, according to the American Academy of Family Physicians 23
Pain patterns, such as dysmenorrhea, deep dyspareunia, and chronic pelvic pain, can be used to support clinical diagnosis, as suggested by the American College of Obstetricians and Gynecologists 23
The depth of endometriosis lesions correlates with pain severity, but pain has little relationship to the type of lesions seen at laparoscopy, as noted by the American Academy of Family Physicians 23

Limitations of Diagnostic Methods

Serum CA-125 has limited utility, especially for minimal or mild disease, though it may help monitor clinical response in patients with confirmed extrauterine disease, as stated by the American Academy of Family Physicians 23

Imaging and Diagnostic Recommendations for Endometriosis

Ultrasound Assessment and O‑RADS Classification

Endometriomas that appear as homogeneous low‑level (ground‑glass) cysts are classified as O‑RADS 2 (benign); however, when the cyst enlarges, changes morphology, or develops a vascular component, referral to an ultrasound specialist or MRI is recommended for further evaluation【24】.

Role of Computed Tomography (CT)

Computed tomography of the pelvis is not indicated for routine diagnosis or surgical planning of endometriosis; its use is limited to situations where life‑threatening complications are suspected【25】.

Imaging Strategies for Abdominal Endometriosis Diagnosis

Diagnostic Accuracy of Current Modalities

Laparoscopy with histologic confirmation remains the gold‑standard for definitive diagnosis because all imaging techniques, including MRI and ultrasound, have limited sensitivity for superficial peritoneal endometriosis. 26
Both transvaginal ultrasound (TVUS) and pelvic MRI reliably detect ovarian endometriomas, providing comparable diagnostic performance. [26][27]
MRI demonstrates poorer diagnostic accuracy for superficial peritoneal disease compared with deep infiltrating lesions. 27

First‑Line Imaging Options

Expanded‑protocol TVUS + transabdominal ultrasound is recommended as a first‑line study when operators have completed a learning curve of ≥ 40 examinations; it evaluates uterosacral ligaments, anterior rectosigmoid wall, and other pelvic structures. This approach is not widely available in the United States. 26
Pelvic MRI without intravenous (IV) contrast is an equally appropriate first‑line alternative; its large field‑of‑view reduces the need for additional imaging studies and offers more automated acquisition than ultrasound. [26][27]

Use of Intravenous Contrast

IV contrast‑enhanced MRI is specifically advised to differentiate endometriomas from ovarian malignancies, given the risk of endometriosis‑associated cancer. 27
IV contrast does not improve detection of deep infiltrating endometriosis; a study found no diagnostic benefit for DE when contrast is added. 27
Moderate bladder distention and vaginal contrast agents can improve lesion conspicuity on MRI. 26

Specialized Imaging for Bowel Involvement

Pelvic MRI can predict the required surgical approach by quantifying lesion length, thickness, and circumferential bowel involvement. 28
Specialized CT techniques (CT with water enema or CT colonography) can identify multifocal or proximal bowel lesions beyond the TVUS field of view, although these methods are not widely accessible. 28

Pitfalls and Contraindicated Modalities

Standard CT of the pelvis has no role in routine endometriosis evaluation and should be reserved only for suspected life‑threatening complications. 28
Conventional “community” TVUS is less effective than expanded‑protocol ultrasound or MRI for mapping deep infiltrating disease; expanded protocols or MRI are required for accurate assessment. 27
A negative imaging study does not exclude endometriosis, especially superficial peritoneal disease, which remains poorly detected across all modalities. Clinical diagnosis based on characteristic symptoms (e.g., dysmenorrhea, dyspareunia, dyschezia, dysuria, chronic pelvic pain) can proceed without surgical confirmation. 26
Pre‑operative imaging is associated with reduced morbidity and mortality by decreasing the incidence of incomplete surgeries that would otherwise require re‑operation. 26

Emerging Technologies

Fluoroestradiol PET imaging, an estrogen‑analog PET tracer, has shown promise in early clinical trials for detecting endometriosis lesions, although it is currently FDA‑approved only for metastatic breast cancer. 26

Clinical Impact of Imaging

Imaging informs treatment planning, helps reduce surgical morbidity, and prevents incomplete resections by accurately identifying deep infiltrating disease that may require bowel or urologic surgery. [26][28]