MRI-Based Scoring System Predicts Surgical Approach in Rectosigmoid Endometriosis

Radiologists Develop a Reliable MRI Tool to Guide Surgical Strategy in Bowel Endometriosis

Key Points

Highlights: 

• A novel MRI-based scoring system was developed to classify rectosigmoid endometriosis according to suspected depth of bowel wall invasion.
• The score shows strong potential for predicting the type of colorectal surgery required. 

Importance:

• Accurately estimating the depth of rectosigmoid endometriosis before surgery is crucial for appropriate surgical planning.
• This MRI scoring system offers a non-invasive method to anticipate whether patients will require partial-thickness discoid excision or segmental bowel resection.

What’s done here:

• The authors retrospectively evaluated 95 patients with surgically confirmed bowel endometriosis between 2018–2022.
• Each pre-treatment MRI was scored by abdominal radiologists using a four-tier system (0–3) reflecting increasing suspicion for muscularis propria invasion.
• The ability of the score to predict surgical intervention was assessed using diagnostic performance metrics.

Key results:

• Score 2 lesions (intermediate thickening; indeterminate muscularis involvement) resulted in 50% of patients undergoing partial-thickness discoid resection.
• Score 3 lesions (definite “mushroom cap sign” or clear muscularis involvement) were strongly predictive of major surgery, with 89% of patients undergoing segmental resection.
• Scores 0 and 1 (no disease or superficial involvement) were associated with no rectosigmoid surgery or only partial-thickness discoid excision.
• Diagnostic performance was high: AUC values were 92.2%, 84.5%, and 93.9% for the reference score and the two independent readers, respectively.

Strength and Limitations:

• Strengths of the study are the non-invasive and practical nature of the scoring system, its high diagnostic accuracy with strong inter-reader agreement, and its good correlation with actual surgical outcomes.
• Limitations of the study are its retrospective single-center design with a relatively small sample size, and the possibility that MRI findings may not fully reflect the true depth of invasion without histopathologic confirmation.

From the Editor-in-Chief – EndoNews

"This study represents an important advancement in the preoperative evaluation of rectosigmoid endometriosis. By proposing a clear MRI scoring system grounded in the suspected depth of bowel wall invasion, the authors address a longstanding challenge in surgical planning: anticipating when a patient will require conservative discoid excision versus segmental resection. The strong correlation between MRI scores and both surgical approach and pathologic depth of invasion—including 100% muscularis propria involvement among cases with MRI score 3—highlights the potential clinical value of this structured framework.

A key strength of the work is its high diagnostic accuracy and excellent inter-reader agreement, demonstrating that the score is both reproducible and practical. The authors’ hybrid approach—pairing qualitative features with quantitative measurements—also provides a foundation for more standardized reporting and more consistent communication between radiologists and surgeons. Their identification of MRI score 2 as the most ambiguous category accurately reflects real-world diagnostic uncertainty and underscores the need for complementary modalities such as bowel-prepared transvaginal ultrasound.

However, interpretation must be tempered by several limitations. The study’s retrospective, single-center design limits generalizability, and the relatively small cohort may not capture the full disease spectrum. Moreover, although MRI can suggest invasion depth, the possibility remains that imaging may not fully reflect the true depth of bowel wall involvement without histopathologic confirmation—an inherent limitation for any non-invasive modality. Prospective, multicenter validation across a diversity of MRI protocols will therefore be essential before the scoring system can be incorporated into routine practice or standardized lexicons.

Despite these constraints, this work lays valuable groundwork for a more unified and predictable approach to evaluating rectosigmoid endometriosis. By offering a common language and a reproducible structure for MRI interpretation, it brings the field closer to achieving more accurate preoperative counseling, better operative preparedness, and ultimately more tailored and safer surgical care for patients."

Lay Summary

Researchers in the United States have developed a new MRI-based scoring system to help predict which type of surgery may be required for patients with rectosigmoid endometriosis.

The scoring system is designed to estimate the likelihood of muscularis propria involvement, a key factor that influences whether a patient needs a conservative discoid excision or a more extensive segmental bowel resection.

In a study published in Abdominal Radiology, a team led by Dr. Wendaline M. VanBuren at the Mayo Clinic analyzed the records and preoperative MRIs of 95 surgically treated patients with bowel endometriosis (median age 36) between May 2018 and June 2022. Each MRI was assigned a score from 0 to 3, reflecting increasing suspicion for deeper bowel wall invasion.

Score 0: no evidence of rectosigmoid endometriosis (16 patients); score 1: minimal serosal tethering without muscularis involvement (14 patients); score 2: intermediate soft tissue thickening with indeterminate muscularis involvement (30 patients) and score 3: definite “mushroom cap sign” or clear muscularis involvement (35 patients).

Surgical outcomes strongly correlated with MRI scores.
Among patients with a score of 2, 50% underwent partial-thickness discoid resection, 17% underwent full-thickness discoid resection, and 33% required segmental resection. In contrast, patients with a score of 3 overwhelmingly required major surgery: 89% underwent segmental resection, confirming the score’s ability to flag deep infiltrating disease. Patients with scores of 0 or 1 either had limited discoid excision or did not require rectosigmoid surgery at all.

The scoring system demonstrated high diagnostic performance, with area under the curve (AUC) values of 92.2%, 84.5%, and 93.9% for the reference radiologist and two independent readers—indicating strong reproducibility and clinical potential. 

Overall, this new MRI scoring system offers a promising non-invasive tool to help surgeons anticipate the depth of bowel involvement and plan the most appropriate intervention for rectosigmoid endometriosis.

Research Source: https://pubmed.ncbi.nlm.nih.gov/40439718/