DDs

The appendix is composed of the same four histological layers of the alimentary canal.

See “Microscopic anatomy” in “Large intestine” for the histological features of a healthy appendix.

Transmural neutrophilic infiltration is the characteristic histological feature of acute appendicitis.

Blood vessel thrombosis, mucosal ulceration, and/or gangrene of the appendiceal wall may also be present.

Ectopic pregnancy

Pseudoappendicitis

Meckel diverticulum

Diverticulitis (especially in elderly patients)

Inflammatory bowel disease

Gastroenteritis

Colon cancer

Urolithiasis and renal colic

Urinary tract infections

Psoas abscess (in patients with a positive psoas sign)

Gynecological diseases (e.g., pelvic inflammatory disease, ovarian cyst)

Uncomplicated appendicitis with adequate management (surgical intervention) has an excellent prognosis.

Perforation and peritonitis: ∼ 1% mortality rate

Up to 20% of patients are found to have a normal appendix following surgery.

The mortality rate is higher (∼ 5%) in elderly patients with complicated appendicitis.