Gut Failure During Pediatric Critical Illness: Toward a Phenotype-Driven Framework for Early Recognition, Prognostication, and Prevention

Gastrointestinal dysfunction is common during critical illness, yet gut failure remains poorly defined, inconsistently diagnosed, and incompletely integrated into organ dysfunction frameworks. Current clinical approaches often recognize gut failure only after overt manifestations such as feeding intolerance, ileus, abdominal distension, gastrointestinal bleeding, or radiographic bowel injury have developed. However, these signs may represent late manifestations of distinct and potentially evolving pathophysiologic pathways. In this narrative review, we propose a phenotype-driven framework for gut failure during critical illness, with emphasis on pediatric critical care. We conceptualize gut failure as a dynamic syndrome comprising overlapping phenotypes: motility-dominant dysfunction, perfusion-ischemic injury, epithelial barrier failure, dysbiosis, absorptive-nutritional failure, treatment-modified dysfunction, and mixed evolving states. Linking these phenotypes to clinical presentation, prognosis, and management may improve early diagnosis and allow clinicians to anticipate progression before irreversible injury occurs. Pediatric patients represent a particularly vulnerable population because gut failure may affect not only short-term outcomes such as infection, mechanical ventilation, and mortality, but also nutrition delivery, growth, microbiome development, and recovery. A phenotype-based approach may shift gut failure from a late symptom-based diagnosis toward an earlier, mechanism-informed, and potentially preventable process.