Preferred Initial Imaging for Suspected Endometriosis
Transvaginal ultrasound (TVUS) is the preferred initial imaging test for a 35-year-old woman with suspected endometriosis. 1, 2
Primary Imaging Recommendation
TVUS should be performed as the first-line imaging modality because it is widely available, cost-effective, and has excellent diagnostic accuracy when performed by skilled operators using standardized protocols. 2, 3
The examination should be performed according to the IDEA (International Deep Endometriosis Analysis) consensus approach, which includes systematic evaluation of the uterus, ovaries, pouch of Douglas, and anterior/posterior pelvic compartments. 2, 3
Transabdominal ultrasound should be added to TVUS to widen the field of view and evaluate structures beyond the transvaginal reach, including the upper urinary tract and gastrointestinal tract. 1
What TVUS Can Detect
Ovarian endometriomas are reliably identified by TVUS, appearing as cysts with low-level internal echoes and echogenic peripheral foci. 4
Deep infiltrating endometriosis (DIE) involving the rectosigmoid colon, vagina, retrocervical area, and bladder can be detected with high sensitivity (84-100% for most sites except bladder). 5
Pouch of Douglas obliteration can be assessed using the real-time "sliding sign" with 89% sensitivity and 92% specificity. 5, 3
Critical Technical Requirements
Bowel preparation before the examination significantly improves detection of bowel lesions and deep endometriosis. 5
The examiner must be specifically trained in endometriosis protocols, as standard "community ultrasound" has significantly lower accuracy compared to specialized protocols. 6, 2
Bilateral kidney assessment is mandatory when deep endometriosis or endometriomas are suspected, as 5-10% of women with DIE have ureteric involvement that can cause silent hydronephrosis. 2, 3
When to Proceed to MRI
MRI pelvis (with or without IV contrast) should be ordered after an indeterminate or negative ultrasound if clinical suspicion remains high. 6
MRI is particularly indicated for complex cases with extensive adhesions, suspected ureteral involvement, or when ultrasound findings are inconclusive. 4
MRI with IV contrast is preferred because it helps differentiate endometriomas from ovarian malignancies and identifies alternative causes of pelvic pain such as fibroids or inflammatory conditions. 1, 6
What NOT to Order
CT has no role in the diagnostic workup of suspected endometriosis and should not be ordered as initial imaging. 1, 6, 7
While CT may incidentally detect endometriosis findings (such as hyperdense adnexal masses or soft tissue bridging from the uterus to the rectum), it is not the appropriate test to order when endometriosis is clinically suspected. 7
Common Pitfalls to Avoid
A negative ultrasound does NOT rule out endometriosis, particularly superficial peritoneal disease, which has poor detection rates on all imaging modalities. 1, 6, 4
Do not skip kidney evaluation when deep endometriosis is suspected, as ureteral obstruction can be asymptomatic and lead to irreversible renal damage. 2
Ensure the ultrasound is performed by an examiner trained in endometriosis protocols, as sensitivity drops dramatically with standard pelvic ultrasound techniques. 6, 2