Small intestinal mucosa in childhood in health and disease.

A great increase in the knowledge of human small intestinal mucosal pathology has resulted from the use of the peroral small intestinal biopsy technique. This paper highlights some different applications of electron microscopy to such biopsy samples in order to obtain diagnostic criteria and to further the understanding of enteric processes in childhood in health and disease. The importance of control data in childhood is emphasized and differences are described between adult and childhood mucosa. The possibilities of quantitative studies at the ultrastructural level and the link between structure and function are demonstrated by studies on microvillous appearance in relation to disaccharidase enzyme levels; the potential for experimental work is shown in studies using tracer molecules to investigate antigen permeability of the small intestine; and finally descriptive observations is highlighted in a section concerned with parasitic, bacterial and viral infections of the small intestine in childhood.