Acute appendicitis

Reviewer: Jaleh Mansouri, M.D. (see Authors page)

Revised: 15 February 2016, last major update August 2012

Copyright: (c) 2003-2016,, Inc.

PubMed Search: Acute appendicitis
Cite this page: Acute appendicitis. website. Accessed June 22nd, 2018.
Definition / general
  • Formerly called typhilitis (typhlitis) (inflammation of cecum)
  • Associated with obstruction in 50-80% of cases, usually due to a fecalith (Hum Pathol 1981;12:870)
  • Also gallstone, tumor, Enterobius vermicularis (pinworm), diffuse lymphoid hyperplasia (children)
  • However, not all cases show clear evidence of lumen obstruction
Clinical features
  • Common in US and Great Britain (Western world); rare in Asia and Africa
  • Usually teenagers or young adults who present with periumbilical to right lower quadrant pain, nausea, vomiting, abdominal tenderness, mild fever, leukocytosis (15-20,000), elevated C reactive protein, elevated sedimentation rate
  • May have right flank pain or pelvic pain with retrocecal appendix
  • Pain in left upper quadrant if malrotated colon
  • Nonclassic presentations occur in very young or very old
  • Associated with reduced bulk / high protein diet
  • Patients with clinical symptoms but histologically normal appendices often have neuronal hypertrophy (Arch Pathol Lab Med 2003;127:573), and increased levels of inflammatory mediators (Arch Pathol Lab Med 2001;125:759)
  • Normal false positive rate for appendectomy is 20% (high false positive rate in women of reproductive age, J Gastroenterol 2006;41:745)
  • Diagnosis: acute inflammation (neutrophils) within appendix
  • Treatment: excision (appendectomy)
  • Obstruction causes increased intraluminal pressure, collapse of draining veins, ischemia, mucosal injury and ulceration, bacterial overgrowth, more edema, more ischemia
  • Not associated with Helicobacter pylori infection (Arch Pathol Lab Med 2000;124:941)
Case reports
Common errors

  • Wall abscess and perforation (2% mortality, higher rate in older populatoin)
  • Rupture, peritonitis, pylephlebitis with thrombosis of portal venous drainage
  • Also liver abscess, bacteremia, formation of sinus tract (often due to Actinomyces)
Gross description
  • Fibrinopurulent exudate on serosa, prominent vessels
  • Lumen may contain blood-tinged pus
  • Variable perforation, mucosal ulceration, fecalith or other obstructing agent
Gross images

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Exudate and hyperemia


Microscopic (histologic) description
  • Mucosal ulceration
  • Minimal (if early) to dense neutrophils in muscularis propria with necrosis, congestion, perivascular neutrophilic infiltrate
  • Late: absent mucosa, necrotic wall, prominent fibrosis, granulation tissue, marked chronic inflammatory infiltrate in wall, thrombosed vessels
Microscopic (histologic) images

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Mucosal inflammation and necrosis

Neutrophils within muscularis propria

Virtual slides

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Periappendiceal abscess

Acute appendicitis

Differential diagnosis
  • Drainage of exudate (Campylobacter) into appendix with neutrophils in mucosa, but not wall
  • Mesenteric lymphadenitis due to Yersinia or viral enterocolitis
  • Systemic viral infection, acute salpingitis, ectopic pregnancy, mittelschmerz, cystic fibrosis, Meckel’s diverticulitis, acute diverticulitis, infarction of greater omentum, chemotherapy induced typhilitis (typhlitis)
  • Appendiceal or colonic neoplasms may sometimes present as appendicitis