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Appendicitis is defined as "Acute inflammation of the appendix. Acute appendicitis is classified as simple, gangrenous, or perforated."[1]

Indigestible food delivered from the small intestine to the large intestine flows into the appendix and is forced out by contraction of the muscular walls of the appendix. The appendix has no known function in humans, but it is thought that, in our evolutionary ancestors, the appendix was important for digesting some tough food like tree bark. If the opening where the appendix attaches to the large intestine becomes blocked, this can lead to appendicitis, accompanied by acute pain, fever, nausea, vomiting and loss of appetite. This is a common condition, with a lifetime occurrence of about 7%.

Because the appendix has no clear role, and because it can be removed surgically without any ill effects, appendectomy is a very common operation, but it is not without risks, particularly if the appendix is perforated.

The rates of unnecessary appendectomy and of perforation have not improved over time[2][3] in spite of increased use of laboratory tests[3] and diagnostic imaging[4].


An Alvarado score (also called MANTRELS score) of less than 3[5] or 5[6][7] makes appendicitis very unlikely - at least if the pretest is low[8]:
Two points each:

  • Abdominal pain that migrates to the right iliac fossa
  • Leukocytosis (more than 10000 white blood cells per microliter)

One point each:

  • Anorexia (loss of appetite) or ketones in the urine
  • Nausea or vomiting
  • Pain on pressure in the right iliac fossa
  • Rebound tenderness
  • Fever of 37.3 °C (99.1 °F) or more
  • Left shift or an increase in the number of immature leukocytes in the peripheral blood

X-ray computed tomography

Spiral x-ray computed tomography with oral and intravenous contrast has accuracy of:[9]

Spiral x-ray computed tomography with oral and intravenous contrast may be equally effective when using amounts of radiation.[10]

Spiral x-ray computed tomography without radiocontrast has accuracy of:[11]


While surgery is definitive, antibiotics may successfully treat some patients.[12]

"Amoxicillin plus clavulanic acid was not non-inferior to emergency appendicectomy for treatment of acute appendicitis" according to a randomized controlled trial.[13] However, peritonitis within 30 days was significantly more frequent in the antibiotic group (8% versus 2%). The recurrence rate of appendicitis within one year in the antibiotic group was 26%.



Appendiceal abscess or phlegmon occurs in 4% of cases.[14] It is controversial whether these patients require an appendectomy.[14]


  1. National Library of Medicine.
  2. Flum DR et al. (2001). "Has misdiagnosis of appendicitis decreased over time? A population-based analysis". JAMA 286: 1748–53. PMID 11594900[e]
  3. 3.0 3.1 Scitovsky AA (1985). "Changes in the costs of treatment of selected illnesses, 1971-1981". Med Care 23: 1345–57. PMID 4087950[e] Cite error: Invalid <ref> tag; name "pmid4087950" defined multiple times with different content
  4. Perez J et al. (2003). "Liberal use of computed tomography scanning does not improve diagnostic accuracy in appendicitis". Am J Surg 185: 194–7. PMID 12620554.
  5. McKay R, Shepherd J (June 2007). "The use of the clinical scoring system by Alvarado in the decision to perform computed tomography for acute appendicitis in the ED". Am J Emerg Med 25 (5): 489–93. DOI:10.1016/j.ajem.2006.08.020. PMID 17543650. Retrieved on 2009-02-14. Research Blogging.
  6. Haldane C (2008). BestBets: The Alvarado Scoring System is an accurate diagnostic tool for appendicitis. BestBets. Retrieved on 2009-02-14.
  7. Ohle R, O'Reilly F, O'Brien KK, Fahey T, Dimitrov BD (2011). "The Alvarado score for predicting acute appendicitis: a systematic review.". BMC Med 9: 139. DOI:10.1186/1741-7015-9-139. PMID 22204638. PMC PMC3299622. Research Blogging.
  8. Ebell MH, Shinholser J (2014). "What Are the Most Clinically Useful Cutoffs for the Alvarado and Pediatric Appendicitis Scores? A Systematic Review.". Ann Emerg Med. DOI:10.1016/j.annemergmed.2014.02.025. PMID 24731432. Research Blogging.
  9. Pickhardt PJ, Lawrence EM, Pooler BD, Bruce RJ (2011). "Diagnostic performance of multidetector computed tomography for suspected acute appendicitis.". Ann Intern Med 154 (12): 789-96. DOI:10.1059/0003-4819-154-12-201106210-00006. PMID 21690593. Research Blogging.
  10. Kim K, Kim YH, Kim SY, Kim S, Lee YJ, Kim KP et al. (2012). "Low-dose abdominal CT for evaluating suspected appendicitis.". N Engl J Med 366 (17): 1596-605. DOI:10.1056/NEJMoa1110734. PMID 22533576. Research Blogging.
  11. Hlibczuk V, Dattaro JA, Jin Z, Falzon L, Brown MD (2009). "Diagnostic Accuracy of Noncontrast Computed Tomography for Appendicitis in Adults: A Systematic Review.". Ann Emerg Med. DOI:10.1016/j.annemergmed.2009.06.509. PMID 19733421. Research Blogging.
  12. Varadhan KK, Humes DJ, Neal KR, Lobo DN (2010). "Antibiotic therapy versus appendectomy for acute appendicitis: a meta-analysis.". World J Surg 34 (2): 199-209. DOI:10.1007/s00268-009-0343-5. PMID 20041249. Research Blogging.
  13. Vons C, Barry C, Maitre S, Pautrat K, Leconte M, Costaglioli B et al. (2011). "Amoxicillin plus clavulanic acid versus appendicectomy for treatment of acute uncomplicated appendicitis: an open-label, non-inferiority, randomised controlled trial.". Lancet 377 (9777): 1573-9. DOI:10.1016/S0140-6736(11)60410-8. PMID 21550483. Research Blogging.
  14. 14.0 14.1 Andersson RE, Petzold MG (2007). "Nonsurgical treatment of appendiceal abscess or phlegmon: a systematic review and meta-analysis". Ann. Surg. 246 (5): 741–8. DOI:10.1097/SLA.0b013e31811f3f9f. PMID 17968164. Research Blogging.