Appendicitis

Appendicitis is an acute inflammatory condition of the vermiform appendix, most commonly caused by obstruction of its lumen. The appendix is a narrow, blind-ended pouch that extends from the cecum, making it particularly prone to obstruction. Causes include fecaliths, lymphoid hyperplasia (often after viral infections), parasites, tumors, or foreign bodies. This obstruction initiates a cascade of pathological changes.

Luminal Obstruction and Early Inflammation

After obstruction, normal mucosal secretions accumulate, increasing intraluminal pressure. This pressure compresses venous outflow before arterial supply, causing congestion and reduced perfusion. Ischemia results in damage to the epithelial lining, leading to ulceration. The weakened mucosal barrier allows gut bacteria, such as Escherichia coli and Bacteroides, to invade deeper layers of the gut.

Bacterial Invasion and Suppurative Inflammation

Bacterial invasion triggers an acute inflammatory response, with neutrophil infiltration into the mucosa and submucosa, a hallmark of suppurative appendicitis. The appendix becomes swollen and filled with pus. Inflammation may begin at the tip but typically spreads to involve the entire organ as pressure and infection increase.

Progression to Ischemia and Gangrene

Continued pressure further impairs arterial blood flow, worsening ischemia. Prolonged lack of oxygen leads to necrosis, resulting in gangrenous appendicitis. If the wall weakens significantly, perforation can appear, releasing infectious contents into the peritoneal cavity and leading to abscess formation or diffuse peritonitis.

Clinical Significance

These sequential events show how simple luminal obstruction can rapidly progress to a surgical emergency requiring prompt diagnosis and treatment.