Changes in the composition of serum bile acid as a predictor of small bowel allograft rejection in rats.

Composition of bile acid was studied as a noninvasive rejection marker after small bowel transplantation (SBT). Orthotopic SBT were performed in rats, and they were divided into four groups: group 1, sham-operated rats; group 2, recipients with isografts; group 3, recipients with allografts treated with FK506; and group 4, recipients with untreated allografts. On postoperative days (POD) 5 and 7, the graft histology, intraluminal bacterial overgrowth, individual bile acids concentration of the recipient serum and bile were examined. On POD 5, early histological findings of acute rejection were observed in group 4, and the ratio of secondary bile acids of this group were significantly higher than the other groups. The bile acid changes were enhanced by bacterial overgrowth on POD 7. The ratio of secondary bile acids changed in relation to acute rejection after SBT, suggesting that they can be useful for early diagnosis of acute SBT allograft rejection.