Acute appendicitis

Acute appendicitis is an acute inflammation of the vermiform appendix. It is very common and keeps general surgeons busy.

Acute appendicitis
Diagnosis in short
Acute appendicitis. H&E stain.
LM	neutrophils in the muscularis propria
LM DDx	adenovirus appendicitis, negative appendectomy, Granulomatous appendicitis, Crohn's disease of the appendix, appendiceal neuroendocrine tumour, mucinous tumour of the appendix
Gross	serosal surface dull, +/-fibrinous exudate, +/-perforation
Site	vermiform appendix
Clinical history	classically periumbilical pain then right lower quadrant pain, usu. younger patients
Signs	rebound tenderness, tenderness at McBurney's point, Rovsing sign, psoas sign, obturator sign
Prevalence	common
Blood work	leukocytosis
Radiology	periappendiceal fat stranding, increased appendiceal diameter
Prognosis	good
Clin. DDx	symptomatic Meckel diverticulum, epiploic appendagitis, ectopic pregnancy, ruptured ovarian cyst, ovarian torsion, pelvic inflammatory disease

General

• Bread 'n butter of general surgery.
• Interesting factoid: appendicitis is considered protective against ulcerative colitis.

Short clinical DDx:

• GI tract:
  • Symptomatic Meckel diverticulum.
  • Epiploic appendagitis.
• Gynecologic tract:
  • Ectopic pregnancy.
  • Ruptured ovarian cyst.
  • Ovarian torsion.
    • Pelvic inflammatory disease.

Gross

Features:

• Serosal surface dull.
• May be perforated (best determined on gross).
• +/-Fibrinous exudate.

Note:

• Normal diameter of appendix (based on CT): 6.6 +/- 1.5 mm.
  • Similar numbers are found in another study.

Image:

• 

  Acute appendicitis. (WC/euthman)

Microscopic

Features:

• Neutrophils in the muscularis propria - key feature.
• +/- Vascular thrombosis (and necrosis) - known as gangrenous appendicitis.
• +/- Findings suggestive of etiology - usu. absent:
  • +/- Fecalith.
  • +/- Viral inclusions (extremely rare)
    • See adenovirus appendicitis.

Note:

• Eosinophils are very common.
  • Appendices with eosinophils but no apparent neutrophils probably represent the same process.

DDx:

• Negative appendectomy - specimen should be submitted in toto, no lymphoid hyperplasia.
• Adenovirus appendicitis - lymphoid hyperplasia.
• Mucinous tumour - usu. apparent on gross.
• Appendiceal neuroendocrine tumour.
• Granulomatous appendicitis.
• Crohn's disease of the appendix.
  • Approximately of 40% colectomies for CD (that include an appendix) have involvement of the appendix.

Images

• 

  Appendicitis - low mag. (WC/Nephron)

• 

  Appendicitis - very high mag. (WC/Nephron)

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VERMIFORM APPENDIX, APPENDECTOMY:
- ACUTE APPENDICITIS.
- ACUTE PERIAPPENDICITIS. 

VERMIFORM APPENDIX, APPENDECTOMY:
- GANGRENOUS APPENDICITIS.
- ACUTE PERIAPPENDICITIS. 

Perforated appendicitis

VERMIFORM APPENDIX, APPENDECTOMY:
- ACUTE APPENDICITIS WITH PERFORATION AND ACUTE PERIAPPENDICITIS.

This is uncommon to see definitively on histology.

Micro

Gangrenous appendicitis

The sections shows appendiceal wall with marked acute transmural inflammation and necrotic appendiceal wall with large collections of neutrophils. Several medium-sized blood vessels are thrombosed. A thick layer of neutrophils cover the serosal aspect.

See also

• Vermiform appendix.