Sensitivity of Contrast-Enhanced Abdominal/Pelvic CT for Endometriosis
Contrast-enhanced CT has no established role in the diagnosis of endometriosis and should not be used for this indication—the ACR Appropriateness Criteria explicitly state there is "no relevant literature to support the use of routine pelvic CT with IV contrast" for suspected endometriosis. 1
Why CT Is Not Recommended for Endometriosis Detection
Standard contrast-enhanced CT of the abdomen and pelvis lacks sufficient sensitivity and specificity for detecting endometriosis lesions. The imaging characteristics of endometriotic implants are nonspecific on CT and overlap extensively with other pathologies, making accurate diagnosis unreliable. 2
Key Limitations of CT for Endometriosis:
No validated sensitivity data exists for standard contrast-enhanced CT in detecting pelvic endometriosis—the ACR guidelines do not provide performance metrics because CT is not considered an appropriate modality for this indication. 1
CT is frequently performed for acute abdominal/pelvic pain but endometriosis features are often missed or misdiagnosed due to their variable and nonspecific appearance. 2
Specialized CT techniques (CT with water enema or CT colonography) show accuracy for rectosigmoid endometriosis specifically, but these protocols are not widely available and are reserved for mapping bowel involvement beyond the field of view of transvaginal ultrasound. 1
Appropriate Imaging Modalities for Endometriosis
The ACR recommends transvaginal ultrasound (TVUS) with expanded protocol or MRI pelvis as first-line imaging, not CT. 3
Performance of Recommended Modalities:
Expanded protocol TVUS demonstrates 81.1% sensitivity and 94.2% specificity for deep infiltrating endometriosis overall, with excellent performance comparable to MRI when performed by trained operators. 4, 3
MRI pelvis without IV contrast shows 90.3% sensitivity and 91% specificity for deep pelvic endometriosis, with location-specific performance of 92.4% sensitivity/94.6% specificity for intestinal endometriosis and 88% sensitivity/83.3% specificity for posterior deep infiltrating disease. 3, 5
MRI with IV contrast is specifically recommended to differentiate endometriomas from ovarian malignancies, but contrast does not improve detection of deep infiltrating endometriosis itself. 3, 5
When CT May Incidentally Detect Endometriosis
While CT is not indicated for endometriosis diagnosis, certain findings may be recognized when CT is performed for other indications:
Ovarian endometriomas may appear as hyperdense adnexal masses, either in the expected ovarian location or posterior to the uterus. 2
Ruptured endometriomas can present with hemoperitoneum on CT. 2
Rectosigmoid involvement may show enhancing soft tissue bridging from the posterior uterine surface to the anterior rectal wall. 2
Acute uterine retroflexion from deep posterior endometriosis may be visible. 2
Small bowel obstruction from endometriotic adhesions or implants may be the presenting finding. 2
Critical Clinical Pitfalls
Do not order CT for suspected endometriosis—it delays appropriate diagnosis and exposes patients to unnecessary radiation without diagnostic benefit. 1, 3
CT is reserved only for suspected life-threatening complications such as bowel obstruction, perforation, or ischemia in patients with known endometriosis. 3, 6
Negative imaging does not exclude endometriosis—all imaging modalities, including MRI and ultrasound, have poor sensitivity for superficial peritoneal disease, which can only be definitively diagnosed at laparoscopy. 3
Clinical diagnosis based on symptoms (dysmenorrhea, dyspareunia, dyschezia, dysuria, chronic pelvic pain) is sufficient to initiate empiric treatment without requiring surgical confirmation. 3