ASA - Intra-Abdominal Bowel Dilation as a Predictor of Severity and Treatment Response in Complex Gastroschisis: Clinical Stratification, a Novel Ovine Model, and First-in-Human Fetal Repair

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Intra-Abdominal Bowel Dilation as a Predictor of Severity and Treatment Response in Complex Gastroschisis: Clinical Stratification, a Novel Ovine Model, and First-in-Human Fetal Repair
*Tomohiro Arai^², *Mary Elizabeth Guerra^¹, *Sourav Bose^¹, *Michael Belfort^³, *Luc Joyeux^¹, *Hui Li^¹, *Swathi Balaji^¹, *Jan Deprest^², Sundeep Keswani^¹
^¹Department of Surgery, Baylor College of Medicine, Houston, Texas; ^²KU Leuven, Leuven; ^³Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas

Objectives: Complex gastroschisis (cGS) carries ~10% infant mortality in the U.S. and near-universal mortality in many low-resource settings. Because most intestinal injury occurs prenatally, fetal intervention is an appealing strategy; however, prenatal risk stratification remains limited. Intra-abdominal bowel dilation (IABD) has been proposed as a biomarker. We hypothesized that IABD identifies fetuses with cGS, serves as a dynamic marker of fetal treatment response, and reflects underlying intestinal remodeling in human and translational systems.
Methods: We retrospectively assessed IABD as a predictor for cGS in 75 human cases. We developed a mid-gestational (75d) ovine model by exteriorizing bowel and applying a 1.5-cm constrictive ring to mimic abdominal wall tethering (n=14). IABD and motility (MRI GI-Quant) were measured before and after fetoscopic repair within 18 days. Intestinal tissue underwent whole-transcriptome analysis focused on extracellular matrix (ECM) pathways. Findings were compared with outcomes from the first human fetoscopic gastroschisis repairs performed under an FDA Phase I trial. Significance set as p<.05.
Results: In humans, IABD≥7 mm at 20-25 weeks' gestation was 100% specific for cGS (sensitivity 13%), confirming that when present, dilation definitively predicts a complex phenotype. In sheep, the constriction model reliably produced cGS (n=7 cGS, 7 fetal demise), recapitulating matted, inflamed bowel and significant dilation (IABD 23.3 vs 5.4mm, p<.001) with reduced motility (GI-Quant score 63 vs 243, p<.01) compared to sham controls. Fetoscopic repair significantly reduced IABD (5.4±1.0 vs 23.2±3.0mm, p<.0001) and improved motility (233±139 vs 63±17, p<.05), normalizing to control levels. Transcriptomic analysis demonstrated ECM dysregulation including altered collagen synthesis, matrix turnover, and mechanotransduction, providing a biologic basis for dilation and motility defects. In the Phase I human trial, two fetuses with IABD>10 mm showed decreased IABD following fetoscopic repair, accompanied by early improvements in intestinal function and overall clinical outcomes compared with historical controls, closely mirroring findings in the ovine model.
Conclusion: IABD is highly specific predictor of cGS and a dynamic indicator of response to in utero repair. Consistent results across human validation, a rigorous translational ovine model, and our initial human clinical experience. Ongoing Phase I enrollment will further define IABD as a central biomarker for fetal therapy in cGS, with the potential to meaningfully improve outcomes for infants affected by this debilitating condition.

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