This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Inflammation of the intestine may affect either the small or the large intestine or any portion of them. Different names being given according to the region affected, enteritis (small intestine), colitis (large), etc. The mucosa and the submucosa are generally involved. If there is involvement of the stomach as well, the condition is known as gastro-enteritis.
The inflammation may be caused by the presence of irritating substances within the gut, as indigestible materials or poisons of various kinds. It may also be due to the presence of certain organic bodies resulting from imperfect digestion and fermentation.
Among the commonest causes of enteritis are bacteria, such as the typhoid, cholera, and colon organisms. The intestinal parasites, particularly the Entamoeba histolytica, can occasion extensive inflammation.
Catarrhal Enteritis may occur in any portion of the small intestine. There is usually a slight congestion with some swelling. The lymphoid follicles are enlarged, there is considerable mucous exudation, and occasionally small ulcerations. There is increased peristalsis on account of the inflammation and the intestinal contents are fluid, as a result of the exudation, and frequently blood stained. Shreds of epithelium may be discharged. In the intestinal wall there is a round-cell infiltration of the mucosa, the lymphoid tissue is increased, and there is an abnormal number of goblet cells.
Follicular Enteritis is frequently a sequel to the catarrhal form. In it there is marked involvement of the solitary lymphoid follicles. They are much swollen, project from the mucous membrane, and sometimes undergo suppuration with the formation of ulcers. Is probably due to infection.
Suppurative Enteritis is characterized by the exudation of pus cells, with round-cell infiltration and focal abscesses in the mucosa and submucosa. May follow a follicular enteritis and show numerous ulcerations of the follicles.
Ulcerative Enteritis may be due to suppuration of the lymphoid follicles in catarrhal or follicular enteritis or to specific infection, as in typhoid, dysentery, tuberculosis, and syphilis.
Pseudomembranous Enteritis is characterized by the formation of a thick, grayish, soft and pulpy covering to the mucosa. Is most common in the large intestine on the edge of the valvulae conniventes. When the membrane sloughs off, there is left exposed an ulcer. The intestinal wall is thickened by edema, hyperemia, and round-cell infiltration. This form is generally seen in dysentery.
Chronic Enteritis may follow the acute form or it may depend upon the persistence of the cause of irritation. It generally involves the small intestine and upper part of the large. The mucosa is thickened, even to the extent of polypoid formations, the lymph-follicles enlarged, and extensive connective-tissue hyperplasia is present. Ulcerations and stellate cicatrices of healed ulcers may be found, particularly in the large intestine. In between the elevated areas of mucosa there are depressed bands of fibrous tissue. The surface of the intestine is covered by a tenacious mucus and the color of the tissue may be very dark on account of the venous congestion. Round-cell infiltration is marked. Instead of hypertrophy there may be an atrophy of the glandular tissue, on account of the contraction of the fibrous tissue. These areas will be marked by the presence of dark almost black pigment. There is generally an atrophy of the muscularis as well.
All forms of enteritis are generally accompanied by diarrhea as a consequence of the increased secretions and peristalsis. There is interference with digestion and nutrition and the general health of the individual suffers. Poisonous substances may form within the intestine.