Lymphocytic follicles and aggregates are a determinant of mucosal damage and duration of diarrhea.

Context: Nonspecific changes (nonspecific chronic inflammation) in patients with chronic diarrhea represent the commonest diagnosis in colorectal biopsy interpretation, but these changes are of little clinical significance.

Objective: To find, within this group, histologic and immunohistologic diagnostic criteria to predict the duration and resolution of diarrhea.

Design: Detailed clinical features and histologic findings were analyzed in a cohort of 47 patients with chronic diarrhea, with near-normal histology and no clear-cut known etiologic agent. Immunohistochemistry to mast cells (CD117) and Treg cells (FOXP3) was also assessed in 39 patients.

Results: Increased number of lymphoid follicles and aggregates, increased number of mast cells, and paucity of Treg were the statistically significant key findings (P  =  .003, P  =  .008, and P  =  .04, respectively). The duration of diarrhea was correlated with the number of large lymphoid follicles and aggregates (P  =  .001, r  =  .48), number of total lymphoid follicles and aggregates (P  =  .003, r  =  .43), density of lymphoid follicles and aggregates (P  =  .009, r  =  .38), and total lymphoid follicles and aggregates per biopsy (P  =  .004, r  =  .42) and the number of mast cells (P  =  .001, r  =  .52). The number of mast cells and Treg cells showed significant difference between resolved and unresolved cases (P  =  .001 and P  =  .01 respectively).

Conclusions: Lymphocytic follicles and aggregates colitis, previously regarded as of negligible diagnostic significance, allows the prediction of the behavior of chronic diarrhea in a subset of patients with nonspecific changes on colonic biopsy. The increased number of mast cells and paucity of Treg cells further helps to identify such unresolved cases.