Sudan S et al. (2007) Calprotectin: a novel noninvasive marker for intestinal allograft monitoring. Ann Surg 246: 311–315

Intestinal failure can be treated successfully by intestinal transplantation if subsequent rejection is avoided. Additional immunosuppression can control mild rejection and prevent complete loss of the graft, which is fatal in more than 50% of patients. Such treatment must be started immediately but diagnosis is difficult. One of the first clinical signs of rejection is diarrhea, but this can also be caused by infectious enteritis or a reaction against drugs or food. As no noninvasive test is currently available, patients presenting with diarrhea must undergo an endoscopic biopsy through a temporary ileostomy, a procedure that can cause serious complications.

It has been proposed that calprotectin levels in stool samples can indicate shedding of intestinal epithelial cells. This intracellular protein is released mainly as a result of cell disruption or death; therefore, Sudan et al. investigated whether calprotectin levels in the succus entericus from intestinal transplant recipients correlated with the onset of early acute rejection.

Calprotectin levels were measured in four groups of patients: 12 with histologic evidence of acute rejection; 5 with viral enteritis; 16 with nonspecific inflammation and 35 with normal allograft histology. Calprotectin levels were significantly higher in patients experiencing rejection and, in two patients, elevated calprotectin levels appeared 6–18 days before histologically detectable signs of rejection. The authors suggest that stool calprotectin levels could be used as the basis of a screening test to enable some patients to avoid unnecessary invasive endoscopy.