Studies of the small bowel surface by scanning electron microscopy in infants with persistent diarrhea

We describe the ultrastructural abnormalities of the small bowel surface in 16 infants with persistent diarrhea. The age range of the patients was 2 t o 10 months, mean 4.8 months. All patients had diarrhea lasting 14 or more days. Bacterial overgrowth of the colonic microflora in the jejunal secreti on, at concentrations above 10(4) colonies/ml, was present in 11 (68.7%) pa tients. The stool culture was positive for an enteropathogenic agent in 8 ( 50.0%) patients: for EPEC O111 in 2, EPEC O119 in 1, EAEC in 1, and Shigell a flexneri in 1; mixed infections due to EPEC O111 and EAEC in 1 patient, E PEC O119 and EAEC in 1 and EPEC O55, EPEC O111, EAEC and Shigella sonnei in 1. Morphological abnormalities in the small bowel mucosa were observed in all 16 patients, varying in intensity from moderate 9 (56.3%) to severe 7 ( 43.7%). The scanning electron microscopic study of small bowel biopsies fro m these subjects showed several surface abnormalities. At low magnification (100X) most of the villi showed mild to moderate stunting, but on several occasions there was subtotal villus atrophy. At higher magnification (7,500 X) photomicrographs showed derangement of the enterocytes; on several occas ions the cell borders were not clearly defined and very often microvilli we re decreased in number and height; in some areas there was a total disappea rance of the microvilli. In half of the patients a mucus-fibrinoid pseudome mbrane was seen partially coating the enterocytes, a finding that provides additional information on the pathophysiology of persistent diarrhea.