Many patients with endometriosis undergo 5-10 ultrasound scans before receiving an accurate diagnosis. The reason? Standard ultrasound is not designed to detect endometriosis lesions. There is, however, an alternative — specialized transvaginal ultrasound with the IDEA protocol — that detects most cases without exploratory surgery.
Why can standard ultrasound miss endometriosis?
Conventional abdominal ultrasound (through the abdominal wall, with a full bladder) has major limitations when it comes to detecting endometriosis:
- Long distance — the probe is far from the pelvic organs
- Insufficient resolution for small lesions (under 5mm)
- Interference from intestinal gas and adipose tissue
- No dynamic evaluation — cannot assess organ mobility or adhesions
- Limited field of view — does not systematically explore all areas
Even standard transvaginal ultrasound (without the IDEA protocol) can miss:
- Superficial peritoneal lesions
- Bowel endometriosis
- Small bladder endometriosis
- Subtle adhesions
— Dr. Alin Constantin
What is the IDEA protocol?
IDEA (International Deep Endometriosis Analysis) is a standardized protocol for the systematic evaluation of endometriosis via transvaginal ultrasound. Published by an international group of experts in 2016, it is now widely used for the non-invasive assessment of endometriosis.
What does the IDEA protocol evaluate?
1. The uterus
- Adenomyosis
- Fibroids
- Uterine anatomy and mobility
2. The ovaries
- Ovarian endometriomas ("chocolate cysts")
- Ovarian reserve
- Ovarian adhesions
3. Sliding sign — mobility assessment
Gentle pressure is applied with the probe to check whether organs "slide" against one another. Absent sliding = adhesions = suspicion of endometriosis.
Assessed:
- Sliding sign between uterus and rectum (pouch of Douglas)
- Sliding sign between uterus and bladder
- Ovarian mobility
4. Posterior compartment
- Pouch of Douglas
- Uterosacral ligaments
- Rectovaginal septum
- Rectum and sigmoid colon (bowel endometriosis)
5. Anterior compartment
- Bladder
- Vesicouterine wall
- Ureters (if affected)
Advantages of non-invasive IDEA diagnosis
- ✓ Non-invasive — no anesthesia, no surgery
- ✓ Usually well tolerated — only mild discomfort
- ✓ Quick — 30-45 minutes
- ✓ Affordable — compared to laparoscopy
- ✓ Repeatable — can be performed anytime for monitoring
- ✓ No surgical risk — unlike exploratory surgery
- ✓ Helps surgical planning — we know exactly what to expect
What can be diagnosed by ultrasound with the IDEA protocol?
- Ovarian endometriomas: high accuracy
- Deep infiltrating endometriosis (DIE): good sensitivity in experienced hands
- Bowel endometriosis nodule: direct visualization
- Adenomyosis: standardized ultrasound criteria
- Pelvic adhesions: indirect signs via sliding sign
- Bladder endometriosis: nodule in the bladder wall
- Deep infiltrating endometriosis (DIE): good sensitivity in experienced hands
What CANNOT be diagnosed by ultrasound?
Ultrasound has its limits:
- Superficial peritoneal endometriosis — small lesions (under 5mm) on the peritoneum may be missed
- Microscopic endometriosis — requires biopsy
- Subtle adhesions — indirect signs, but no visual confirmation
For these cases, laparoscopy with histology remains the reference method for confirmation. However, IDEA ultrasound helps identify most cases that need surgical planning.
Who should perform the ultrasound?
The examiner's experience is essential. The IDEA protocol requires specific training and continuous practice. An IDEA ultrasound performed by a gynecologist without endometriosis expertise can miss lesions that a specialist would identify immediately.
What to look for in an ultrasonographer for endometriosis:
- Specific training in the IDEA protocol
- High volume of endometriosis cases (at least 100/year)
- Publications or presentations in the field
- Direct collaboration with endometriosis surgeons
- Use of modern high-resolution ultrasound equipment
— Dr. Alin Constantin
When should you schedule a specialized ultrasound?
Book a transvaginal ultrasound with the IDEA protocol if you have:
- Severe menstrual pain that does not respond to anti-inflammatories
- Chronic pelvic pain
- Deep dyspareunia (pain during intercourse)
- Difficulty conceiving
- Cyclical digestive or urinary symptoms
- A prior diagnosis of endometriosis — for follow-up or surgical planning
- Preoperative — for complete mapping of lesions
How to prepare for the ultrasound
- Schedule the ultrasound in the first half of the cycle (days 5-12), when visibility is best
- No special preparation is required
- Bring previous ultrasounds for comparison
- Make a list of your symptoms in advance
- Empty your bladder beforehand (for comfort)
Dr. Alin Constantin performs transvaginal ultrasound with the IDEA protocol at Monza Hospital, Bucharest. Non-invasive, precise diagnosis in 45 minutes.
📅 Book Pre-Consultation →Related articles
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Last updated: July 2026 • Author: Dr. Alin Constantin, VP European Endometriosis League
