Parenteral versus enteral nutrition: morphological changes in human adult intestinal mucosa

In animal experiments total parenteral nutrition induces an atrophy of the small intestinal mucosa. In humans morphological data are few and controversial. Therefore, the aim of this study was to investigate the effect of parenteral nutrition on the intestinal mucosa of human adults. For this purpose samples of the proximal jejunum of a) patients with chronic pancreatitis receiving total parenteral nutrition as presurgical treatment, b) enterally nourished patients without (controls) and c) with chronic pancreatitis were compared using light and scanning electron microscopy. Statistical differences were assessed applying computer-assisted morphometry. The results demonstrated that the thickness of the jejunal mucosa decreased already in enterally nourished patients with chronic pancreatitis. However, after total parenteral nutrition the decrease (atrophy) was enhanced due to a strong reduction in villus height albeit the crypt length increased. In addition, scanning electron microscopy revealed distinctive changes in mucosal surface pattern, whereby finger-like villi were replaced by leaf-like villi and by long, winding bifurcating ridges. Cell shedding was absent. In conclusion, total parenteral nutrition in humans induces 1) an atrophy and 2) a remodelling of the intestinal mucosa (epithelium and lamina propria) with a decrease in the absorbing surface. These alterations involve both cell proliferation and cell shedding. The response of the mucosa to parenteral nutrition is immediate and the effect of the treatment in bringing about morphological alterations is more efficacious at the beginning than in the successive period. The basic disorder (chronic pancreatitis) of the patients nourished parenterally contributes to mucosal atrophy, but not to remodelling.