Ultrastructure of intestinal lymphatics in Crohn's disease

The fine structure of intestinal lymphatics in four patients with Crohn's disease and in two control subjects is described. Although obstructed lacteals are considered to be of major importance in the pathogenesis of regional enteritis, no detailed electron microscopic studies of lymphatic capillaries in this disease could be found. Even though both open and closed intercellular junctions were observed in the normal intestinal lymphatics, only closed junctions were noted in the mucosal and submucosal lymphatic capillaries in patients with regional enteritis. A heavy accumulation of protein rich lymph at the abluminal surface of lymphatic capillaries was consistently seen. None of the control lymphatics showed a similar alteration. The described fine structural changes indicate a decreased permeability of the lymphatic wall. Reduced lymphatic permeability could be a contributing element in the development of submucosal edema, a major microscopic feature of Crohn's disease.