• Clinical science
  • Physician

Acute appendicitis


Acute appendicitis refers to acute inflammation of the appendix, typically due to an obstruction of the appendiceal lumen. In both children and adults, it is the most common cause of acute abdomen requiring emergency surgical intervention. The characteristic features of acute appendicitis are periumbilical abdominal pain that migrates to the right lower quadrant (RLQ), anorexia, nausea, fever, and RLQ tenderness. In association with neutrophilic leukocytosis, these features are sufficient to make a clinical diagnosis of acute appendicitis. Imaging (e.g., abdominal CT with IV contrast, abdominal ultrasonography) may be considered if the clinical features are inconclusive. The current standard of management of acute appendicitis is emergency appendectomy (open or laparoscopic) and broad-spectrum antibiotics. Conservative management, which includes bowel rest, antibiotics, and analgesics, is indicated in patients with an inflammatory appendiceal mass (phlegmon) or an appendiceal abscess because surgical intervention is associated with a higher risk of complications in these patient groups. Interval appendectomy 6–12 weeks after resolution of the acute episode can be performed in these patients to prevent a recurrence.


  • Common cause of acute abdomen [1]
  • Lifetime risk: ∼ 8%
  • Peak incidence: 10–19 years of age [2]
  • Sex: >


Epidemiological data refers to the US, unless otherwise specified.


Caused by obstruction of the appendiceal lumen due to: [3]

  • Lymphoid tissue hyperplasia; (60% of cases): most common cause in children and young adults
  • Fecalith; and fecal stasis (35% of cases): most common cause in adult
  • Neoplasm; (uncommon): more likely in patients > 50 years of age [4]
  • Parasitic infestation (uncommon): e.g., Enterobius vermicularis, Ascaris lumbricoides, and species of the Taenia and Schistosoma genera [5]



  • Obstructed proximal appendiceal lumen (closed-loop obstruction), resulting in: [7]
    • Stasis of mucosal secretions bacterial multiplication and local inflammation → transmural spread of infection → clinical features of appendicitis
    • Increased intraluminal pressure → obstruction of veins edema of the appendiceal walls → obstruction of capillaries ischemia → gangrenous appendicitis with/without perforation
  • Inflammation can spread to serosa, leading to peritonitis


Clinical features

The location of the pain may be variable as the appendix's location varies, especially in pregnant women. [10]



  • Acute appendicitis is often a clinical diagnosis.
  • Laboratory tests
  • Imaging
    • Abdominal ultrasound ;: non-compressible and enlarged appendix (> 6–8 mm)
      • Target sign
        • Loss or absence of appendix in advanced or phlegmonous appendicitis
      • Wall thickening
      • Edema surrounding the appendix
      • Appendix not compressible
      • In perforation → intra-abdominal free fluid
    • Abdominal CT scan (∼ 98% sensitivity): periappendiceal streaking and enlarged appendix

Abnormal urine analysis does not necessarily rule out appendicitis!

Appendicitis is a clinical diagnosis. Further examination, such as blood tests and imaging, is not essential to diagnosis but may be considered if the diagnosis is uncertain!References:[7][2][6]


  • The appendix is composed of the same four histological layers of the alimentary canal.
  • See “Microscopic anatomy” in large intestine for the histological features of a healthy appendix.
  • Transmural neutrophilic infiltration is the characteristic histological feature of acute appendicitis.
  • Blood vessel thrombosis, mucosal ulceration, and/or gangrene of the appendiceal wall may also be present.

Differential diagnoses

Right-sided carcinoma of the colon may manifest as acute appendicitis! [12]


The differential diagnoses listed here are not exhaustive.


General approach


Suspected appendicitis warrants surgical intervention!

  • Surgical approach may be laparoscopic or open and is decided on a case-by-case basis


Acute management checklist


Inflammatory appendiceal mass (appendiceal phlegmon)

  • Description: an ill-defined mass of inflammatory periappendiceal tissue
  • Clinical features: manifests as a tender mass in the RLQ in a patient who is not acutely ill
  • Management: conservative (bowel rest, IV fluids, IV antibiotics, with/without interval appendectomy)

Gangrenous appendicitis

  • Description: irreversible necrosis of the appendiceal wall
  • Clinical features
    • Manifests with high-grade fever, tachycardia, severe RLQ pain and tenderness
    • Typically diagnosed intraoperatively: appendix appears mottled purple
  • Management: immediate appendectomy and IV antibiotics

Perforated appendix

Appendiceal abscess



We list the most important complications. The selection is not exhaustive.


  • Uncomplicated appendicitis with adequate management (surgical intervention) has an excellent prognosis. [8]
  • Perforation and peritonitis: ∼ 1% mortality rate [8]
  • Up to 20% of patients are found to have a normal appendix following surgery. [7]
  • The mortality rate is higher (∼ 5%) in elderly patients with complicated appendicitis. [8]


Special patient groups

Appendicitis in children [10][18]

  • The reliability of signs and symptoms in children is lower.
    • The most reliable symptoms: emesis and duration of pain
    • The most reliable signs: abdominal tenderness and pain with walking, jumping or coughing.
  • Ultrasound is the diagnostic procedure of choice.

Appendicitis in pregnancy [19][10]

  • Atypical (higher) pain localization
  • Perforated appendix is associated with a higher risk of fetal loss
  • Ultrasound is the diagnostic procedure of choice

Appendicitis in older patients [20]

  • Clinical presentation
  • Consider they usually have multiple comorbidities.
  • CT scan or MRI imaging is preferred because of atypical presentation and higher malignancy rates

Children, pregnant women, and the elderly are at a higher risk of perforation!

  • 1. Feldman M, Friedman LS, Brandt LJ. Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management. Philadelphia, PA, USA: Elsevier Saunders; 2016.
  • 2. Martin RF. Acute appendicitis in adults: Clinical manifestations and differential diagnosis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/acute-appendicitis-in-adults-clinical-manifestations-and-differential-diagnosis#H5346248. Last updated February 5, 2016. Accessed December 12, 2016.
  • 3. Tao Le, Vikas Bhushan, Deol M, Reyes G. First Aid for the USMLE Step 2 CK, Tenth Edition. New York: McGraw-Hill Education; 2018.
  • 4. Lamber LA. Appendiceal Cancer and Tumors. https://rarediseases.org/rare-diseases/appendiceal-cancer-tumors/. Updated January 1, 2018. Accessed June 5, 2019.
  • 5. Altun E, Avci V, Azatçam M. Parasitic infestation in appendicitis. A retrospective analysis of 660 patients and brief literature review. Saudi Med J. 2017; 38(3): pp. 314–318. doi: 10.15537/smj.2017.3.18061.
  • 6. Le T, Bhushan V, Chen V, King M. First Aid for the USMLE Step 2 CK. McGraw-Hill Education; 2015.
  • 7. Agabegi SS, Agabegi ED. Step-Up To Medicine. Baltimore, MD, USA: Wolters Kluwer Health; 2015.
  • 8. Craig S. Appendicitis. In: Brenner BE. Appendicitis. New York, NY: WebMD. http://emedicine.medscape.com/article/773895-treatment. Updated December 27, 2015. Accessed December 14, 2016.
  • 9. Struller F, Weinreich F-J, Horvath P, et al. Peritoneal innervation: embryology and functional anatomy. Pleura and Peritoneum. 2017; 2(4): pp. 153–161. doi: 10.1515/pp-2017-0024.
  • 10. Snyder MJ, Guthrie M, Cagle S. Acute Appendicitis: Efficient Diagnosis and Management. Am Fam Physician. 2018; 98(1): pp. 25–33. pmid: 30215950.
  • 11. McMillan JA, Feigin RD, DeAngelis C, Jones MD. Oski's Pediatrics. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.
  • 12. Deken MM, de Bie SH, de Noo ME. Acute appendicitis of coloncarcinoom?. Ned Tijdschr Geneeskd. 2016. url: https://www.ntvg.nl/artikelen/acute-appendicitis-coloncarcinoom/extended_abstract.
  • 13. Smink D, Soybel DI. Management of acute appendicitis in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/management-of-acute-appendicitis-in-adults?source=see_link#H770943. Last updated October 24, 2016. Accessed December 14, 2016.
  • 14. Rushfeldt CF, Sveinbjørnsson B, Søreide K, Vonen B. Risk of anastomotic leakage with use of NSAIDs after gastrointestinal surgery. Int J Colorectal Dis. 2011; 26(12): pp. 1501–1509. doi: 10.1007/s00384-011-1285-6.
  • 15. Bratzler DW, Dellinger EP, Olsen KM, et al. Clinical practice guidelines for antimicrobial prophylaxis in surgery. Am J Health Syst Pharm. 2013; 70(3): pp. 195–283. doi: 10.2146/ajhp120568.
  • 16. Pinto et al. CT Evaluation of Appendicitis and Its Complications: Imaging Techniques and Key Diagnostic Findings. American Journal of Roentgenology. 2005; 185(2): pp. 406–417. doi: 10.2214/ajr.185.2.01850406.
  • 17. Abdel-Halim AW. Passing the USMLE: Clinical Knowledge. Springer Science+Business Media; 2009.
  • 18. Kharbanda AB, Stevenson MD, Macias CG, et al. Interrater Reliability of Clinical Findings in Children With Possible Appendicitis. Pediatrics. 2012; 129(4): pp. 695–700. doi: 10.1542/peds.2011-2037.
  • 19. Pastore PA, Loomis DM, Sauret J. Appendicitis in Pregnancy. J Am Board Fam Med. 2006; 19(6): pp. 621–626. doi: 10.3122/jabfm.19.6.621.
  • 20. Di Saverio et al. WSES Jerusalem guidelines for diagnosis and treatment of acute appendicitis. World Journal of Emergency Surgery. 2016; 11(1). doi: 10.1186/s13017-016-0090-5.
  • Appendix. https://www.histology.leeds.ac.uk/digestive/appendix.php. Accessed June 3, 2019.
  • Gorter RR, Eker HH, Gorter-Stam MAW, et al. Diagnosis and management of acute appendicitis. EAES consensus development conference 2015. Surg Endosc. 2016; 30(11): pp. 4668–4690. doi: 10.1007/s00464-016-5245-7.
  • Quartey B. Interval appendectomy in adults: A necessary evil?. Journal of Emergencies, Trauma, and Shock. 2012; 5(3): p. 213. doi: 10.4103/0974-2700.99683.
  • Demetrashvili Z, Kenchadze G, Pipia I, Ekaladze E, Kamkamidze G. Management of Appendiceal Mass and Abscess. An 11-Year Experience. Int Surg. 2015; 100(6): pp. 1021–1025. doi: 10.9738/intsurg-d-14-00179.1.
  • Tannoury J. Treatment options of inflammatory appendiceal masses in adults. World Journal of Gastroenterology. 2013; 19(25): p. 3942. doi: 10.3748/wjg.v19.i25.3942.
  • Rushing A, Bugaev N, Jones C, et al. Management of acute appendicitis in adults. Journal of Trauma and Acute Care Surgery. 2019; 87(1): pp. 214–224. doi: 10.1097/ta.0000000000002270.
  • Solomkin JS, Mazuski JE, Bradley JS, et al. Diagnosis and management of complicated intra-abdominal infection in adults and children: guidelines by the Surgical Infection Society and the Infectious Diseases Society of America. Clin Infect Dis. 2010; 50(2): pp. 133–164. doi: 10.1086/649554.
  • Kumar V, Abbas AK, Aster JC. Robbins & Cotran Pathologic Basis of Disease. Philadelphia, PA: Elsevier Saunders; 2015.
  • Mui LM, Ng CSH, Wong SKH, et al. OPTIMUM DURATION OF PROPHYLACTIC ANTIBIOTICS IN ACUTE NON-PERFORATED APPENDICITIS. ANZ J Surg. 2005; 75(6): pp. 425–428. doi: 10.1111/j.1445-2197.2005.03397.x.
  • Craig S. Appendicitis Medication. In: Brenner BE. Appendicitis Medication. New York, NY: WebMD. https://emedicine.medscape.com/article/773895-medication#1. Updated June 23, 2018. Accessed June 11, 2019.
  • Perez K, Allen S. Complicated appendicitis and considerations for interval appendectomy. Journal of the american academy of physician assistance. 2018; 31. url: https://www.deepdyve.com/lp/wolters-kluwer-health/complicated-appendicitis-and-considerations-for-interval-appendectomy-uRzXCPbOLE?articleList=%2Fsearch%3Fquery%3Dinterval%2Bappendectomy.
  • Salminen P, Tuominen R, Paajanen H, et al. Five-Year Follow-up of Antibiotic Therapy for Uncomplicated Acute Appendicitis in the APPAC Randomized Clinical Trial. JAMA. 2018; 320(12): p. 1259. doi: 10.1001/jama.2018.13201.
  • Brown C, Kang L, Kim S. Percutaneous Drainage of Abdominal and Pelvic Abscesses in Children. Seminars in Interventional Radiology. 2012; 29(04): pp. 286–294. doi: 10.1055/s-0032-1330062.
  • Garcia EM, Camacho MA, et al. American College of Radiology ACR Appropriateness Criteria® Right Lower Quadrant Pain-Suspected Appendicitis. https://acsearch.acr.org/docs/69357/Narrative/. Updated January 1, 2018. Accessed June 11, 2019.
  • Martin RF, Kang SK. Acute Appendicitis in Adults: Diagnostic Evaluation. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/acute-appendicitis-in-adults-diagnostic-evaluation. Last updated May 30, 2018. Accessed January 13, 2019.
  • D'Souza N. Appendicitis. BMJ clinical evidence. 2011; 2011. pmid: 21477397.
  • Addis et al. The epidemiology of appendicitis and appendectomy in the United States. Am J Epidemiol. 1990; 132(5): pp. 910–925. doi: 10.1093/oxfordjournals.aje.a115734.
  • Willekens et al. The Normal Appendix on CT: Does Size Matter?. PLoS ONE. 2014; 9(5): p. e96476. doi: 10.1371/journal.pone.0096476.
  • Sharma and Knipe. Appendix. https://radiopaedia.org/articles/appendix-1?lang=us. Accessed June 4, 2019.
  • Howell set al. Clinical Policy: Critical Issues in the Evaluation and Management of Emergency Department Patients With Suspected Appendicitis. Ann Emerg Med. 2010; 55(1): pp. 71–116. doi: 10.1016/j.annemergmed.2009.10.004.
  • Herold G. Internal Medicine. Cologne, Germany: Herold G; 2014.
last updated 03/26/2020
{{uncollapseSections(['piaLs4', 'IiaYG4', 'riafG4', 'HiaKG4', 'siatG4', 'Fiagt4', '8iaOt4', 'uiapt4', 'Eia8t4', 'ch1a1g0', 'viaAt4', 'Dia1F4', '9iaNF4'])}}