International grading scheme for acute rejection in small bowel transplantation: implementation and experience at the University of Miami.

In 2003, an international collection of pathologists and clinicians proposed a unified grading system for acute cellular rejection in endoscopically derived small intestine allograft biopsies. This grading system was implemented at the University of Miami over the past 2 years and the results are presented herein. A total of 1136 small bowel allograft biopsies with sufficient tissue for analysis were obtained from 123 hospitalized, clinic, and referral patients. The overall most common diagnosis assessing all time periods was grade IND (40%), and grade 1 rejection or greater was present in 19% percent of biopsies. A suspected vascular component to the acute rejection as identified by specific mucosal vascular changes was present in 6% of cases. Clinical decision making was very consistent with different grades. Our experience has confirmed that this new grading system is reliable and identifies clinical subsets of patients that can receive different therapy. We recommend that this international grading system be implemented for acute cellular rejection in bowel allografts as a means to standardize pathological assessment of alloimmune-induced graft injury, which will allow comparisons between different centers and clinical trials.