Gastric distension is the enlargement of the stomach, and can be due to a number of causes. Gastric distension is the enlargement of the stomach, and can be due to a number of causes. Physiologic (normal) gastric distension occurs when eating. Distension of the upper stomach stimulates the secretion of stomach acid, while distension of the lower stomach stimulates gastrin secretion. Distension of the stomach also stimulates the secretion of ghrelin.