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Appendix

Appendicitis

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.

General
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● 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
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● 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)

Pathophysiology
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● 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
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● Associated with Kaposi’s sarcoma of appendix (Arch Pathol Lab Med 1991;115:1157)

Complications
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● 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
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● 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


Fecalith

Micro description
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● 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
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Mucosal inflammation and necrosis


Neutrophils within muscularis propria

Vitual slides
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Periappendiceal abscess

   
Acute appendicitis

Differential diagnosis
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● 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

End of Appendix > Appendicitis > Acute appendicitis

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