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Session:: ePosters-Mon120-M8: Benign Abdominal

EP914 - Intraoperative Ultrasound for Bowel Deep Infiltrating Endometriosis: Impact of Saline Instillation on Diagnostic Accuracy

Monday, May 11, 2026
1:41 PM - 1:46 PM ET

    ePoster Presenter(s)

  • Michael A. Wright, MD

    Fellow
    University of South Florida
    University of South Florida
    Tampa, FL, United States

    Disclosure information not submitted.

    View ePoster

    • Author(s)

  • Taylor L. Garza, MD

    Resident
    University of South Florida
    University of South Florida
    Tampa, FL, United States

    Disclosure information not submitted.

  • Alexia Benson, MD

    Research Fellow
    University of South Florida
    University of South Florida
    Tampa, FL, United States

    Disclosure information not submitted.

  • EG

    Ethan Green, MD

    Resident Physician
    University of South Florida
    Tampa, Florida, United States

    Disclosure information not submitted.

  • EM

    Emad Mikhail, MD, FACOG, FACS

    Professor
    University of South Florida
    Tampa, Florida, United States

    Disclosure information not submitted.

    • Senior Author(s)

  • Robert D. Bennett, MD

    Attending Physician
    University of South Florida
    Tampa, Florida, United States

    All disclosed relationships have been reviewed and managed prior to the start of this activity. Any relevant relationships will be listed below. This individual has no financial relationships to disclose

Purpose/Background: Deep infiltrating endometriosis (DIE) is a severe form of endometriosis in which endometrial tissue invades the bowel wall, causing pain, dyschezia, and infertility. Accurate intraoperative assessment of lesions is critical, as management ranges from conservative shaving to discoid or segmental resection based on depth of invasion and lesion length. Incomplete excision risks recurrence, while unnecessary resection increases morbidity.

Preoperative imaging with transvaginal ultrasound or MRI is useful but limited by fibrosis and distorted anatomy. Intraoperative ultrasound (IOUS) offers real-time visualization of lesion depth and margins, potentially providing critical information for intraoperative decision-making, thus avoiding unnecessary bowel resection and ensuring complete excision. Invasion deeper than the serosa risks incomplete resection with shaving and warrants discoid excision or segmental resection depending on lesion length.

A prior study at our institution showed 58% concordance for depth of invasion between IOUS and pathology. This follow-up study evaluated whether intraluminal saline improves IOUS accuracy in assessing depth of invasion, and whether lesion length was accurately assessed to drive appropriate surgical treatment.

Methods/Interventions: A prospective cohort study was conducted at a tertiary referral center in women undergoing surgery for rectosigmoid DIE. IOUS was performed after rectal instillation of 100-200 mL normal saline to distend the lumen. One or two representative still images were captured and later de-identified and independently reviewed by two surgeons blinded to pathology. The reference standard was histologic depth of invasion and lesion length. Primary outcomes were reader accuracy (depth of invasion: serosa vs deeper than serosa; length: >3 cm vs < 3 cm). Secondary outcomes were inter-rater reliability and accuracy based on number of images available.

Results/Outcomes: 16 patients underwent IOUS. Mean age was 36 years (range, 22-51) and mean BMI 26 kg/m² (range, 19-37). Final pathology showed invasion to the submucosa in 9 (56%) and muscularis propria in 7 (44%) cases.

Surgeon A correctly identified depth of invasion in 14/16 cases (87.5%), and Surgeon B in 9/16 (56.3%). If only deeper estimated depth of invasion between the two surgeons was considered, as is done in the OR, depth of invasion was correctly estimated 93.8% of the time. Interobserver agreement occurred in 9/16 cases (56.3%), with joint assessment correct in 88.9%. Lesion length was accurately assessed in 62.5% of cases. Ability to accurately detect depth of invasion was enhanced for Surgeon A (71.4% vs 100%), but it remained similar for Surgeon B (57.1% vs 55.6%) when additional images were available for review.

Conclusion/Discussion: IOUS remains a valuable adjunct for guiding resection extent in bowel endometriosis. The addition of intraluminal saline improved the ability to determine depth of invasion with relation to the serosa, but increased interobserver variability. Accuracy increased when only the deeper estimated depth of invasion between surgeons was considered, as is done intraoperatively. This highlights the critical nature of multidisciplinary care. Surgeon B was more accurate when provided with two images, suggesting that multiple images may enhance interpretation, similar to the continuous, real-time assessment performed in the operating room. Further refinement of technique and training may improve the utility of IOUS for DIE.

Figure 1. Intraoperative ultrasound evaluation of endometriosis depth of invasion on the colon