Acute appendicitis

What it is

Acute appendicitis is inflammation of the vermiform appendix, typically starting from the inner lining and spreading. The appendix is funnel-shaped in infants, with less obstruction risk, and peak incidence is during adolescence, due to lymphoid follicle growth. Obstruction leads to lumen dilation and thickening, intraluminal bacterial overgrowth, then inflammation, ischemia, gangrene and potential perforation.

The stages are written twice and the two lists differ. One page names four:

1. Intact.
2. Perforated.
3. Localized mass, the phlegmon.
4. Abscess.

The Senior Clerkship student manual sets out the spectrum in five:

1. Obstruction of the appendiceal lumen.
2. Suppurative appendicitis.
3. Gangrenous appendicitis.
4. Perforated appendicitis.
5. Phlegmonous appendicitis or abscess.

The same manual adds spontaneously resolving appendicitis, recurrent appendicitis and chronic appendicitis to that spectrum.

Causes and risk

The common causes are lymphoid tissue hyperplasia (60%), most common in children and young adults, and appendiceal fecalith with fecal stasis (35%), most common in adults. Less common are neoplasms, more likely in patients > 50 years, and parasitic infections, e.g. Enterobius vermicularis and Ascaris lumbricoides.