Objective: To determine whether plasma amino acids may be used as markers of intestinal acute cellular rejection (ACR) using a model of segmental allogenic small bowel transplantation (SBT) in pigs.Summary Background Data: To date, there is no noninvasive or relatively non invasive biomarker for the diagnosis of ACR which remains a major barrier to improving the clinical results of SBT. As the small intestine is one of the main organ involved in metabolism of amino acids, our working hypothesis was that ACR could be associated with significant changes of plasma amino acids levels.Material and methods: Sixteen female pigs were divided into 2 groups: group 1 (n=8), controls, segmental autotransplantation; group 2 (n=8), allotransplantation, nonimmunosuppressed recipients. Intestinal specimens for histological studies were obtained at the end of cold flushing (T0), and on postoperative day 8 (T1). Plasma amino acids levels were measured on samples harvested at T0 and T1. Results: In group 1, intestinal histology revealed no significant changes between T0 and T1 specimens. In contrast, in group 2, graft histology revealed moderate to severe rejection on T1 specimens in all cases. Four plasma amino acids were significantly correlated with the occurrence of acute intestinal rejection: phenylalanine, aspartate, citrulline, and taurine. The threshold of each plasma amino acid variation that best discriminated absence from presence of acute intestinal rejection was determined for each marker with its sensitivity and specificity. A score was determined. An ACR was found in 100% of cases when this score was equal or over 2. Conclusion: Our study suggests for the first time that four plasma amino acid levels may be used in combination as markers of intestinal rejection