Ultrasound or MRI for Deep Endometriosis: ISUOG/IDEA 2024 Consensus

Clinical Significance of the 2024 Consensus

The International ISUOG/IDEA 2024 Consensus establishes a practical approach to a question that regularly arises before surgery: is transvaginal ultrasound sufficient, or is MRI needed for mapping deep endometriosis? The key takeaway: the method is chosen not based on competition but on the task, availability of expertise, and completeness of the answer. Expert TV-US is considered the initial method for pelvic deep endometriosis; MRI enhances the value of routing in complex, incomplete, or discordant cases.

What to Consider as the Goal of Imaging

The goal of the study is not only to confirm the presence of endometriosis but to describe the disease anatomy for surgical planning and informed tactical choice. The report should reflect the localization of lesions, involvement of anterior and posterior compartments, signs of adhesions, the condition of the ovaries and uterus, presence of adenomyosis, involvement of the bowel, bladder, and ureters. A negative imaging result does not exclude superficial peritoneal endometriosis, so the report should clearly distinguish between the absence of visualized deep lesions and the absence of the disease as a whole.

TV-US: First-Line Method

Transvaginal ultrasound is convenient for initial mapping, dynamic assessment of painful areas, and detecting signs of organ fixation. In expert execution, it allows evaluation of the uterus, ovaries, endometriomas, ovarian mobility, the state of the Douglas pouch, anterior compartment, vagina, rectovaginal area, uterosacral ligaments, and rectosigmoid colon. The practical advantage of TV-US is the ability to immediately correlate the image with local tenderness and perform dynamic tests, including assessing organ sliding.

When to Add MRI

MRI is advisable if expert TV-US is unavailable, technically impossible, or provides an incomplete map of lesions. MRI is also useful when there is suspicion of a multi-compartment process, complex post-surgical anatomy, extensive adhesions, high or difficult-to-visualize lesions, and when a single preoperative document is needed for a multidisciplinary team. In the consensus logic, MRI does not replace ultrasound but addresses its limitations: pelvic overview, reproducibility of the map, and clarification of extent beyond the accessible ultrasound window.

Practical Algorithm for Method Selection

1. Initial Stage: Expert TV-US following a structured protocol in a patient suspected of deep endometriosis.
2. If the map is complete: The surgeon receives a description of compartments, lesion sizes, bowel and urinary tract involvement; MRI is not mandatory just to confirm already clear data.
3. If the map is incomplete: MRI is prescribed focusing on areas that ultrasound could not reliably assess.
4. If a complex surgery is planned: Ultrasound and MRI may be used together, especially if colorectal or urological surgeon involvement is likely.
5. If imaging is negative but clinical symptoms are pronounced: The limitations of the method should be noted, and it should be remembered that superficial lesions may not be detected.

IDEA Compartmental Protocol

The IDEA approach is important as it transforms the study from a free description into a surgical map. The physician sequentially evaluates the uterus and adnexa, signs of adhesions and limited mobility, the state of the Douglas pouch, and the presence of deep lesions in the anterior and posterior compartments. For the surgeon, particularly significant are: obliteration of the Douglas pouch, ovarian fixation, involvement of uterosacral ligaments, torus, vagina, rectovaginal area, bowel, bladder, and ureters.

#Enzian: How to Code Findings

The consensus supports the use of classification systems that help standardize language among specialists. For deep endometriosis, #Enzian is practically useful: it codes anatomical compartments and lesion size class. This does not replace a detailed textual report but facilitates comparison of ultrasound, MRI, and surgical data.

What to Include in the Ultrasound or MRI Protocol

• Method of study and limitations: transvaginal access, need for transabdominal addition, technical factors.
• Uterus: position, mobility, signs of adenomyosis, relation to the posterior compartment.
• Ovaries: endometriomas, fixation, contact between ovaries and uterus, signs of adhesions.
• Douglas pouch: free, partially or completely obliterated according to dynamic assessment.
• Anterior compartment: bladder, vesicouterine space, ureters if involvement is suspected.
• Posterior compartment: torus, uterosacral ligaments, vagina, rectovaginal area, bowel.
• For bowel lesion: localization, extent descriptively, depth of wall involvement, distance to anal verge, signs of lumen narrowing if assessed.
• Final map: IDEA compartments and, if used, #Enzian code.

How to Formulate a Conclusion for the Surgeon

The optimal conclusion should answer surgical questions: where is the lesion located, which organs are fixed, is there obliteration of the Douglas pouch, are the bowel, bladder, or ureters involved, will a multidisciplinary operation be required. Formulations only like "signs of endometriosis" without an anatomical map are undesirable. If ultrasound and MRI data differ, the protocol should indicate which areas are reliably assessed by each method and where diagnostic uncertainty remains.

Conclusion for Preoperative Mapping

For most patients suspected of pelvic deep endometriosis, a rational initial strategy is expert TV-US following the IDEA protocol. MRI is added not "for everyone before surgery," but in cases of incomplete visualization, complex anatomy, probable multi-compartment involvement, or the need to clarify the map for multidisciplinary intervention. A unified language of description — IDEA plus #Enzian — makes the results of ultrasound, MRI, and surgery comparable.