Acute Appendicitis

by Ozlem Dikme


About 7% of the population develops appendicitis in their lives. Males are affected 1.4 times higher than females, and teenagers more than adults (3:2). The incidence rises gradually from birth, peaks in the late teens, and declines in the elders. It occurs in all age groups but most frequently between the age of 10 and 30. Prevalence is higher in countries with diet habits low in fiber and high in refined carbohydrates. Low dietary fiber causes fecalith formation and obstruction of the appendicular lumen.

Case Presentation

A previously healthy 22-year-old male was brought to the emergency department (ED) with recently-started abdominal pain. He had not eaten anything since that morning due to loss of appetite. He was nauseated and vomited three times. His abdominal pain started around the umbilicus and epigastric area. His pain increased as it moved towards his right lower quadrant (RLQ). The maximum pain was felt on the right iliac fossa. He had not taken any medication. His social history revealed that he was non-drinker, non-smoker and did not use any illicit drugs. His diet mostly consisted of carbohydrates. The past and family histories were unremarkable. His blood pressure was 120/70 mmHg, pulse rate was 100/min, the temperature was 37.8°C (100°F), and respiration rate was 22/min. Physical examination showed normal bowel sounds, tenderness and voluntary guarding, particularly over the right iliac fossa. The costa-vertebral angles were not tender. Oral intake was stopped, intravenous (IV) catheter was inserted, blood and urine tests were planned, and fluid therapy was started. The urinalysis was normal. White blood cell (WBC) count was 14,500 with 89% polymorphous and 11% lymphocytes. The ultrasonography (USG) showed a non-compressible tubular structure of 9 mm in diameter at RLQ. He admitted to the surgical ward with the diagnosis of acute appendicitis.

Q: Can you name the finding in the given ultrasound?


Very superficial appendix location. It is around 1,5-2 cm deep. The window is transverse view (or short axis) of appendicitis. Although there is no measurement in this video, you can estimate the diameter of appendicitis which is in the center and looks like a target (TARGET SIGN).


Critical Bedside Actions and General Approach

The general approach to a patient with possible acute appendicitis must start with the patient stabilization. Fortunately, the most of the patients come with stable clinical presentation except pain. Some patients may present late. In this situation perforation is a possibility. Therefore diffuse abdominal infection, systemic infection, even sepsis/septic shock can be another priority for the physician. After the ABC evaluation, focused gastrointestinal and pelvic orientation follows. Depending on the patient needs, critical actions necessary in the initial ABC evaluation can be applied. However, placing IV catheters, starting fluid therapy are the priority in most of the cases. Oral intake should be stopped. Pain medication and application of antibiotics may be considered in the early phase depending on the patient situation.

The possibility of acute appendicitis must be explained, and the patient’s approval should be obtained for further steps. The evaluation should include laboratory tests and imaging. Count blood cell (CBC) and c-reactive protein (CRP) are generally not specific to diagnose, but they may be useful to confirm or exclude the differential diagnoses. USG or computed tomography is possible imaging modalities.

History and Physical Examination Hints

Abdominal pain is the most common complaint. It typically starts periumbilical or epigastric, then migrates to the RLQ. It is the most discriminating feature of the patient’s history. Its’ sensitivity and specificity are approximately 80%; the positive likelihood ratio is 3.18, the negative likelihood ratio is 0.5. Patients typically avoid moving because it worsens their pain. The classic history of anorexia, periumbilical pain followed by nausea, RLQ pain, and vomiting occurs in only 50% of cases. Nausea is present in 61-92% of patients, anorexia in 74-78%. Vomiting almost always follows the pain. Diarrhea or constipation is noted in as many as 18% of patients. In up to 50% of cases, local tenderness of Mc Burney’s point and rebound tenderness may be present. Typical physical findings are rebound tenderness, pain with percussion, guarding and rigidity. RLQ tenderness is seen in 96% of patients, but it is nonspecific. Other signs of peritoneal irritation are triggered RLQ pain with palpation of the left lower quadrant (Rovsing sign), with internal and external rotation of the flexed right hip (Obturator sign), with the extension of the right hip (Psoas sign), with cough (Dunphy sign) or with dropping from standing on toes to the heels (Markle Sign).

Differential Diagnoses

Many different specific diseases cause abdominal pain. The below list is given in alphabetical order. We advise you that look for other specific disease entity chapters to understand presentation, diagnosis and treatment differences.

  • Acute Cholecystitis or Biliary Colic
  • Acute Gastritis or Peptic Ulcer Disease
  • Colonic carcinoma
  • Diverticulitis
  • Gastroenteritis
  • Inflammatory Bowel Disease (Crohn Disease, Ulcerative Colitis)
  • Inguinal hernia
  • Intussusception
  • Meckel Diverticulum
  • Mesenteric adenitis
  • Mesenteric ischemia
  • Omental torsion
  • Pancreatitis
  • Perforated viscus
  • Rectus sheath hematoma
  • Tubo-ovarian pathologies (Ectopic pregnancy, Pelvic inflammatory disease, Abscess, Endometriosis, Ovarian cyst/torsion, Uterine leiomyomata)
  • Typhoid Fever
  • Ureterolithiasis or Urinary tract infection

Emergency Diagnostic Tests and Interpretation

Appendicitis is a clinical diagnosis. However, some laboratory tests may help emergency physicians in the decision-making process. Each test has some pros and cons. Therefore, your clinical history and exam should be the main part of your decision-making process. Relying on laboratory tests may mislead you in some cases.

Count Blood Cell (CBC) is an easily accessible and inexpensive test, but it is nonspecific. Studies consistently show that WBC count is greater than 10500/mm3 of 80-85% adult patients with acute appendicitis. Also, the neutrophil count is higher than 75% in 78% of patients. CBC shows different likelihood ratios (LR) for different WBC levels. LR of WBC of 9-11000 is 0.29. However, WBC of 11-13000 has 2.8 LR.

C-reactive protein (CRP) is useful, and it usually is higher than 1 mg/dL. However, it cannot detect the site of infection. Therefore, it is not specific to appendicitis. Studies show that sensitivity of CRP is between 93% and 96.6% for acute appendicitis. A normal CRP level has a negative predictive value of 97-100% for appendicitis in the patients with symptoms longer than 24 hours. Investigators have also studied the combinations of WBC count, CRP and neutrophil count to reliably rule out the diagnosis of acute appendicitis. Patients with a WBC count below 10000/mm3 and a CRP below 6 to 12 mg/dL are unlikely to have acute appendicitis (Negative likelihood ratio: 0.09). Patients with a WBC count above 10000/mm3 and a CRP above 8 mg/dL were likely to have acute appendicitis (positive likelihood ratio: 23.32).

Urinalysis may differentiate diagnoses such as urinary tract infections. However, the appendix has a relationship with the right ureter, and in some cases, pyuria may not refer to only urinary infections. Pyuria may occur in cases of appendicitis, but severe pyuria marks more likely urinary tract infections. Additionally, proteinuria and hematuria in urinalysis usually suggest genitourinary or hematological disorders. Women of childbearing age must have pregnancy evaluated. Ectopic pregnancy should be in your mind always.

Computed tomography (CT) has 94% sensitivity and 95% specificity and shows higher diagnostic accuracy over USG (Sensitivity: 88%, specificity: 94%) for acute appendicitis. A large, single-center study found that CT has a high rate of sensitivity and specificity (98.5% and 98%, respectively) for acute appendicitis. Though the use of IV and oral contrast may increase sensitivity, it may prolong ED stays, cause allergic reactions and vomiting. Therefore, in adults, abdominal and pelvic CT may be performed with or without contrast.

A healthy appendix usually cannot be viewed by Ultrasonography (USG). In the case of acute appendicitis, the USG typically demonstrates a non-compressible tubular structure of 7-9 mm in diameter in the RLQ. However, USG is not as accurate as CT. USG is the first choice, especially in pediatric patients, pregnant females, and slender patients. Additionally, if a gynecologic pathology is more likely than acute appendicitis in females, USG can be the initial test to detect gynecologic pathologies such as ectopic pregnancy, ovarian cysts or other female reproductive system pathologies. If the operator is an experienced ultrasonographer, it may be the first imaging method. It is also important to emphasize that USG is an operator-dependent modality.

Ultrasound images show the increased size of appendicitis (below). More than 6 mm is considered abnormal.

51.2 - abdominal - pain - appendicitis ultrasound 2 51.1 - abdominal - pain - appendicitis ultrasound

The below ultrasound video shows transverse and longitudinal views of appendicitis in the same sequence. The appendix is located 3-4 cm deep from the skin surface. This video does not include measurement. However, the reported diameter was 8 mm, the diameter reaches more than 1 cm (10 mm) in some slices (Courtesy of Ekrem Musalar, for more information about the case please click here).

Plain radiographs are not specific or cost-effective. It may visualize an appendicolith (It is highly suggestive of appendicitis but only seen in fewer than 10% of patients) or air-fluid level on RLQ location.

If USG is equivocal, magnetic resonance imaging (MRI) should be considered in pregnant patients. Its’ disadvantages are long scan times, high cost, and limited availability. Some researchers suggest MRI instead of USG in pediatric patients. MRI’s (100%) sensitivity is found higher than USG (76%) in pediatric patients with acute appendicitis.

Emergency Treatment Options

Very few patients require aggressive resuscitation during the initial evaluation (ABC phase). All patients with suspected dehydration or septicemia must receive IV access and aggressive crystalloid therapy. Additionally, parenteral antiemetics and analgesics should be administered. Prophylactic antibiotics should be given to cover gram-negative and anaerobic organisms.

One of the important global discussion is analgesic use in appendicitis. There is still disagreement between different physician groups, especially emergency physicians and surgeons in some facilities. 2011 Cochrane review reported that “The use of analgesia for acute abdominal pain does not mask clinical findings, nor does it delay diagnosis.” However, only recommended analgesics are opioids in these patients.

Pediatric, Geriatric, and Pregnant Patient Considerations

Appendicitis has relatively high misdiagnosis rates at both extremes of age. In children, the misdiagnosis rate is 25-30%. The most common misdiagnoses are gastroenteritis and respiratory tract infections. The early symptoms like loss of appetite or vomiting are non-specific. They may easily lead the physician to other diagnoses such as gastroenteritis, urinary or respiratory infections.

Ten percents of the appendectomies are performed in the elderly. Misdiagnosis rates are high in this age group too. Elders initially relate their symptoms to their comorbidities. As a result, late presentation to ED may cause diagnostic delays. Additionally, ongoing drugs’ side effects may mask their acute condition. Therefore, a late presentation or insignificance of symptoms should not dissuade the clinician from the diagnosis. The diagnostic delay relates to increased mortality and morbidity. The mortality rates range from 0.1% to 1% in children, and it rises above 20% in patients older than 70 years. Overall, the perforation rate varies from 16% to 40%. Younger children have a higher perforation rate between 50-85%. Diagnostic delays may increase perforation rates up to 55-70% in patients older than 50 years.

The appendicitis incidence in the pregnant remains unchanged compared to the general population, but the changes in the presentation may delay the diagnosis. During pregnancy, appendix replaces toward the right kidney and rises above the iliac crest at about 4.5 months of gestation. RLQ pain and tenderness may occur in the first trimester, but RUQ or flank pain may dominate later. The symptoms are similar to the first-trimester pregnancy symptoms such as nausea, vomiting, and anorexia. The physicians should consider appendicitis if these symptoms reappear later in pregnancy. However, WBC count is not reliable in pregnancy because of the physiologic leucocytosis. Imaging modalities USG or MRI can use for the diagnosis.

Decision Making

Clinical findings guide risk stratification. Risk stratification scores guide diagnostic modalities and disposition decisions such as discharge, observation or surgical consultation. The Alvarado score is a well-known classification for appendicitis (Table).

Alvarado Score In Acute Appendicitis

Anorexia or acetone (in the urine)1
Nausea or vomiting1
SignsTenderness in right lower quadrant2
Rebound pain1
Elevation of temperature (>37.3°C measured orally)1
LaboratoryLeukocytosis (>10,000/mm3)2
Shift to the left (>75% neutrophils)1
Total Score10
1-4 Appendicitis unlikely
5-6 Appendicitis possible
7-8 Appendicitis probable
9-10 Appendicitis very probable
Adopted from Alvarado A. A practical score for the early diagnosis of acute appendicitis. Ann Emerg Med. 1986;15(5):557-564. Please read the original article for further information.


Disposition Decisions

Patients with minimal physical findings and a strong alternative diagnosis or previous multiple episodes of similar pain are considered low risk. In low-risk patients, the best course of action is advising on signs of appendicitis and arranging close follow-up in 12 to 24 hours. Discharged patients should start on a liquid diet and advance to solids when their symptoms improve. Patients with non-specific abdominal pain, who require significant doses of opiates should be considered for admission. Equivocal patients mostly consist of women of childbearing age, men, and children with atypical signs. They should be considered for diagnostic testing or active observation. Men and children with classic presentations are at high risk and gain little benefit from further imaging. Emergency physician should consult the patient with general surgeon without delay. Acute appendicitis is the most common reason for emergent abdominal surgery and appendectomy remains the only curative treatment. Antibiotic treatment without appendectomy may be sufficient therapy for uncomplicated appendicitis, especially in the pediatric population.

References And Further Reading

  • Wolfe JM, Henneman PL. Acute Appendicitis, Chapter 93. In: Marx JA, Hockberger RS, Walls RM, editors. Rosen’s Emergency Medicine Concepts and Clinical Practice, 8th Philadelphia: Elsevier; 2014:1225-1232.
  • Yeh B. Evidence-based emergency medicine/rational clinical examination abstract. Does this adult patient have appendicitis? Ann Emerg Med.2008;52(3):301-303.
  • Howell JM, Eddy OL, Lukens TW, Thiessen ME, Weingart SD, Decker WW. Clinical policy: Critical issues in the evaluation and management of emergency department patients with suspected appendicitis. Ann Emerg Med. 2010;55(1):71-116.
  • Andersson RE. Meta-analysis of the clinical and laboratory diagnosis of appendicitis. Br J Surg2004;91(1):28-37.
  • Grönroos JM. Do normal leucocyte count and C-reactive protein value exclude acute appendicitis in children? Acta Paediatr.2001;90(6):649-651.
  • McGory ML, Zingmond DS, Nanayakkara D, Maggard MA, Ko CY. Negative appendectomy rate: influence of CT scans. Am Surg.2005;71(10):803-8.
  • Harswick C, Uyenishi AA, Kordick MF, Chan SB. Clinical guidelines, computed tomography scan, and negative appendectomies: a case series. Am J Emerg Med. 2006;24(1):68-72.
  • Frei SP, Bond WF, Bazuro RK, Richardson DM, Sierzega GM, Reed JF. Appendicitis outcomes with increasing computed tomographic scanning. Am J Emerg Med.2008;26(1):39-44.
  • Pickhardt PJ, Lawrence EM, Pooler BD, Bruce RJ. Diagnostic performance of multidetector computed tomography for suspected acute appendicitis. Ann Intern Med.2011;154(12):789-796.
  • Kepner AM, Bacasnot JV, Stahlman BA. Intravenous contrast alone vs intravenous and oral contrast computed tomography for the diagnosis of appendicitis in adult ED patients. Am J Emerg Med.2012;30(9):1765-1773.
  • Brenner DJ, Hall EJ. Computed tomography–an increasing source of radiation exposure. N Engl J Med.2007;357(22):2277-2284.
  • Zilbert NR, Stamell EF, Ezon I, Schlager A, Ginsburg HB, Nadler EP. Management and outcomes for children with acute appendicitis differ by hospital type: areas for improvement at public hospitals. Clin Pediatr (Phila).2009;48(5):499-504.
  • Doria AS, Moineddin R, Kellenberger CJ et al. US or CT for Diagnosis of Appendicitis in Children and Adults? A Meta-Analysis. 2006;241(1):83-94.
  • Thieme ME, Leeuwenburgh MM, Valdehueza ZD et al. Diagnostic accuracy and patient acceptance of MRI in children with suspected appendicitis. Eur Radiol.2014;24(3):630-637.
  • Manterola C, Vial M, Moraga J, Astudillo P. Analgesia in patients with acute abdominal pain. Cochrane Database Syst Rev.2011;19(1):CD005660.
  • Alvarado A. A practical score for the early diagnosis of acute appendicitis. Ann Emerg Med.1986;15(5):557-564.
  • Repplinger MD, Golden SK, Ebinger A, Svenson JE. 65 Comparison of Appendicitis Clinical Scoring Systems With Physician-Determined Likelihood of Appendicitis. Ann Emerg Med.2014;64(4):24
  • Horst JA, Trehan I, Warner BW, Cohn BG. Can Children with Uncomplicated Acute Appendicitis Be Treated With Antibiotics Instead of an Appendectomy? Ann Emerg Med.2015;66(2):119-122.
  • Manterola C, Vial M, Moraga J, Astudillo P. Analgesia in patients with acute abdominal pain. Cochrane Database of Systematic Reviews 2011, Issue 1. Art. No.: CD005660. DOI: 10.1002/14651858.CD005660.pub3

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