Small bowel transplantation: current status and new developments in allograft monitoring

Gut microbiota and its implications in small bowel transplantation

The gut microbiota is mainly composed of a diverse population of commensal bacterial species and plays a pivotal role in the maintenance of intestinal homeostasis, immune modulation and metabolism. The influence of the gut microbiota on solid organ transplantation has recently been recognized. In fact, several studies indicated that acute and chronic allograft rejection in small bowel transplantation (SBT) is closely associated with the alterations in microbial patterns in the gut. In this review, we focused on the recent findings regarding alterations in the microbiota following SBTand the potential roles of these alterations in the development of acute and chronic allograft rejection. We also reviewed important advances with respect to the interplays between the microbiota and host immune systems in SBT. Furthermore, we explored the potential of the gut microbiota as a microbial marker and/or therapeutic target for the predication and intervention of allograft rejection and chronic dysfunction. Given that current research on the gut microbiota has become increasingly sophisticated and comprehensive, large cohort studies employing metagenomic analysis and multivariate linkage should be designed for the characterization of host-microbe interaction and causality between microbiota alterations and clinical outcomes in SBT. The findings are expected to provide valuable insights into the role of gut microbiota in the development of allograft rejection and other transplant-related complications and introduce novel therapeutic targets and treatment approaches in clinical practice.

Treatment of intestinal failure: intestinal transplantation

Over the past 15 years, intestinal transplantation for the treatment of intestinal failure has changed from a desperate last-ditch effort into a standard therapy for which a good outcome is expected. Patient survival after intestinal transplantation has improved in the past 3-5 years and now approaches that of other solid organ allograft recipients, including liver and kidney, and is similar to survival on permanent therapy with parenteral nutrition. Complications are more common and often more severe during the initial hospitalization period after intestinal transplantation than they are after transplantation of other solid organs. After intestinal transplantation the initial hospitalization period is, therefore, usually 3-8 weeks long. Nearly all patients discharged after intestinal transplantation have good allograft function and have been weaned from total parenteral nutrition. The cost of the initial hospitalization period is one to two times the cost of permanent total parenteral nutrition for 1 year, which means that, in most cases, intestinal transplantation is cost-saving within 2 years of transplantation. In addition, quality of life after intestinal transplantation, as determined by standardized quality of life measures, is good or normal.

Calprotectin: a novel noninvasive marker for intestinal allograft monitoring

OBJECTIVE

To identify a noninvasive screening test for intestinal allograft monitoring.

SUMMARY BACKGROUND DATA

Intestinal allograft rejection is difficult to distinguish from other causes of diarrhea and can rapidly lead to severe exfoliation or death. Protocol biopsies are standard for allograft monitoring but may cause serious complications. No noninvasive test has shown clinical utility for monitoring of the intestinal allograft.

METHODS

Calprotectin levels (n = 68) were measured in this pilot study from ileostomy effluent in patients with histologic evidence of acute rejection (n = 12), viral enteritis (n = 5), and nonspecific inflammation (n = 16) and compared with those with normal allograft histology (n = 35).

RESULTS

Median stool calprotectin levels from patients with rejection were significantly higher than those from patients with viral enteritis or normal biopsies [198 mg/kg compared with 7 and 19 mg/kg, respectively (P = 0.0002)]. Receiver operator characteristics suggest the optimal cut-off level to distinguish rejection from other diagnoses is 92 mg/kg with specificity of 77% and sensitivity of 83%. Although false-positive results occurred in 26% of patients with normal biopsies and 30% with nonspecific changes, no treated episode of acute rejection was below the cutoff. In addition, in 2 patients with serial levels, elevations in the calprotectin levels preceded histologic changes by 6 to 18 days.

CONCLUSIONS

Low stool calprotectin levels correlate well with a low risk for intestinal allograft rejection. If confirmed, biopsies may be reserved in the future for confirmation of rejection, eliminating protocol biopsies, and immunosuppressive changes could potentially be made before allograft injury.