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Acute appendicitis

Reviewer: Jaleh Mansouri, M.D. (see Reviewers page)
Revised: 19 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● 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

● Associated with Kaposiís sarcoma of appendix (Arch Pathol Lab Med 1991;115:1157)


● 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

Exudate and hyperemia


Micro 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

Micro images

Mucosal inflammation and necrosis

Neutrophils within muscularis propria

Vitual slides

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, Meckelís diverticulitis, acute diverticulitis, infarction of greater omentum, chemotherapy induced typhilitis (typhlitis)
● Appendiceal or colonic neoplasms may sometimes present as appendicitis

End of Appendix > Appendicitis > Acute appendicitis

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