Researches of a rectum of pigs with nonspecific gastroenteritis were conducted. For the experiment among weaners animals with clinical signs of gastroenteritis were selected. To establish histological and morphometric changes of the rectum at the microscopic level the material was obtained from slaughtered and dead animals. The mucous membrane of pigs’ rectum was investigated by the standard histologic and histochemical techniques. The conducted research of histologic preparations of a mucous membrane of a thick gut in patients with chronic postgasterocolitis of a noninfectious etiology allowed to reveal in general in comparison with normal morphological features, characteristic for this colitis, namely: the increase of amount of the imposed slime on superficial epithelial cells and in a gleam of crypts; superficial epithelial cells with a border with a proteinaceous distrofic changes; increase in superficial and cryptal epithelium of scyphoid exocrinocyte with the strengthened release of slime; increase of number of lymphocytes, eosinophil and neutrophil granulocytes among superficial epithelial cells; activation of mitotic division of undifferentiated epithelial cells of intestinal glands; increase in density of inflammatory infiltrate in own plate; increase in infiltrate quantity of lymphocytes, plasmocyte, macrophages of eosinophil and neutrophil granulocytes; decrease in an infiltrate of number of labrocyte; the hypostasis and a loss offibration of own plates which accompanied by the expansion and congestion of its vessels.