Enterocyte Injury and Acute Gastrointestinal Dysfunction in Critical Illness

Enterocyte Injury and Acute Gastrointestinal Dysfunction in Critical Illness: A Prospective Observational Study of Blood and Urinary Intestinal Fatty Acid-Binding Protein(Implications for Sepsis Heterogeneity）

Acute gastrointestinal injury (AGI) is a common but not fully understood organ dysfunction in critically ill patients. Current AGI grading systems rely primarily on clinical presentation and feeding tolerance, which are inherently subjective and may not accurately reflect the underlying biological severity of intestinal damage.

Intestinal fatty acid-binding protein (I-FABP) is a protein expressed almost exclusively in the cytoplasm of mature small intestinal epithelial cells. In cases of ischemia, inflammation, or mechanical injury, I-FABP is rapidly released into the bloodstream and subsequently excreted in the urine. These characteristics make I-FABP a highly specific biomarker for intestinal epithelial cell injury and intestinal ischemia.

A prospective study combining paired blood and urine I-FABP measurements, standardized AGI assessment, and careful consideration of surgical status was conducted to elucidate the role of intestinal epithelial cell injury in acute gastrointestinal dysfunction.

This study is a prospective observational cohort study conducted in an adult intensive care unit. Biological samples and clinical data will be prospectively collected according to a pre-defined protocol, without any intervention other than standard treatment.

Primary objective: To prospectively assess the association between serum and urinary I-FABP levels and the severity of acute gastrointestinal injury in critically ill patients.

Secondary objectives: To investigate the relationship between serum and urinary I-FABP levels and clinical outcomes (including severe AGI and mortality); to explore whether the intestinal epithelial cell injury patterns reflected by serum and urinary I-FABP are associated with different sepsis subphenotypes; and to evaluate the impact of gastrointestinal surgery on I-FABP levels and its modifying effect on the association between I-FABP and AGI severity.

Inclusion Criteria:

• 1、 Age ≥18 years.
• 2 、Admission to the ICU with an expected ICU stay ≥48 hours.
• 3 、Availability of paired plasma and urine samples within 24 hours of ICU admission.
• 4 、Feasible daily gastrointestinal function assessment to complete AGI grading (ESICM definition).

Exclusion Criteria:

• 1、 Pre-existing inflammatory bowel disease.
• 2 、Short bowel syndrome.
• 3、 Chronic intestinal failure requiring long-term parenteral nutrition.
• 4、 Pregnancy.
• 5 、Refusal or withdrawal of informed consent.