Plasma citrulline after small bowel transplantation: effect of time from transplantation, acute cellular rejection, and renal failure

Background Plasma citrulline concentration ( CIT ) depends on its synthesis by enterocytes and its catabolism by renal tubules. To evaluate CIT applicability as a marker of acute cellular rejection ( ACR ) after intestinal transplantation ( IT x), CIT was investigated according to time from IT x, episodes of ACR , and creatinine clearance ( C r C l). Methods Twenty‐four adult IT x recipients were prospectively studied. The results were compared with those of 19 healthy controls ( HC s) and of 29 patients with chronic renal failure ( CRF ). Results In IT x recipients, CIT was lower than in HC s during the first two postoperative weeks; it then progressively increased and reached the range observed in HC s, approximately between the 31st and the 45th postoperative day. A positive association with postoperative days ( R  = 0.63; p < 0.0001) and a negative association with C r C l ( R  = −0.57; p < 0.0001) were observed. CIT was higher in patients with CRF than in HC s (p < 0.0001). CIT sensitivity and specificity in detecting ACR after the 45th postoperative day were 38% and 83%, using CIT threshold observed in HC s, and 69% and 77%, respectively, using CIT threshold adjusted for CRF degree. Conclusions Adjusting CIT threshold for CRF degree almost doubled the sensitivity of CIT as a non‐invasive marker of ACR in IT x recipients.