This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Appendicitis, Inflammation Of The Appendix, is quite common. The lumen of the appendix being so small, it is easily obstructed by foreign bodies or by edema. The blood-supply is poor, so nutrition is readily affected. Foreign bodies, 26 as inspissated feces or seeds, may set up an irritation, but inflammation is more commonly the result of the entrance of micro-organisms. Those most commonly found are streptococci, staphylococci and the colon bacillus. Anerobic forms, also, probably play an important part. Their entrance may be facilitated by lesions of the mucosa caused by foreign bodies. The organisms pass through the mucous membrane, penetrate the lymphoid tissue, and set up an acute inflammation with round-cell infiltration. Catarrhal appendicitis is characterized by slight swelling and minute erosions of the mucosa. The muscular and serous coats will show slight infiltration and the lumen will contain epithelial and pus cells. In the more severe form the appendix is much increased in size as a result of a thickening of the walls, not* of a dilatation of the lumen. The walls are hyperemic, infiltrated with pus and fibrin, and the peritoneal coat is covered with fibrin. In the necrotic or gangrenous variety the inflammatory processes are destructive. The mucosa is destroyed and the muscular and serous layers are soon attacked. The inflammation involves neighboring surfaces and a fibrinous peritonitis develops. This may be local, and by giving rise to adhesions between adjacent tissues no further extension takes place. The process may be very rapid and perforation follow before any restricting adhesions form; this is accompanied by a general and frequently fatal peritonitis.
Fig. 151. - Acute Appendicitis with Round-cell Infiltration and Hyperplasia of Connective Tissue in all of the Coats (Stengel).
In large part the round cells of the mucosa and submucosa belong to the normal lymphoid tissue of these parts.
In interstitial appendicitis there is a tendency toward excessive connective-tissue formation which generally terminates as a chronic thickening.
Appendicitis may recover spontaneously with nothing more than a slight thickening of the walls or obliteration of the lumen. Adhesions may form, and by interfering with the surrounding organs give rise to various disturbances. The appendix may rupture with local or general peritonitis or there may form a localized abscess.