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Acute appendicitis

Last updated: September 24, 2021

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Acute appendicitis is the acute inflammation of the appendix, typically due to an obstruction of the appendiceal lumen. It is the most common cause of acute abdomen requiring emergency surgical intervention in both children and adults. The characteristic features of acute appendicitis are periumbilical abdominal pain that migrates to the right lower quadrant (RLQ), anorexia, nausea, fever, and RLQ tenderness. When seen alongside neutrophilic leukocytosis, these features are sufficient to make a clinical diagnosis using appendicitis scoring systems to estimate the likelihood of appendicitis. Imaging (e.g., abdominal CT with IV contrast, abdominal ultrasonography) may be considered if the clinical diagnosis is uncertain. The current standard of management of acute uncomplicated appendicitis is appendectomy within 24 hours of diagnosis (laparoscopic or open) and antibiotics. Emergency appendectomy is indicated for patients with systemic complications. Nonoperative management (NOM), 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 6–8 weeks following resolution of the acute episode may be considered in these patients to prevent a recurrence or if there is concern for an underlying appendiceal tumor.

References:[2][3]

Epidemiological data refers to the US, unless otherwise specified.

Caused by obstruction of the appendiceal lumen due to:

The location of the pain may be variable as the appendix's location varies, especially in pregnant women. [9]

The following recommendations apply to adult patients and are consistent with the 2020 World Society of Emergency Surgery (WSES) appendicitis guidelines, the 2018 American Association for the Surgery of Trauma (AAST) appendicitis guidelines, and the 2010 American College of Emergency Physicians (ACEP) clinical policy on acute appendicitis. See “Appendicitis in children” for information about pediatric patients. [10][11][12]

Initial management [10][11][13][14]

Subsequent management [10][11][13][14]

Diagnostic imaging is often performed for most patients. A selective and individualized approach is generally recommended to minimize patient exposure to radiation and expedite care. [10][11][15][16]

Low likelihood of appendicitis

  • Associated scores: AIR score ≤ 4, Alvarado score ≤ 2–4
  • Management: Additional testing for appendicitis may not be required. [10]
  • Next steps: Determine disposition. [11]
    • Consider discharge home with follow-up within 24 hours in select patients (e.g., motivated adults < 40 years old with clinical stability and no red flags for abdominal pain) [10][16][17]
    • Consider observation, reassessment (e.g., every 6–8 hours), and/or diagnostic imaging for:
      • Suspected early appendicitis
      • Unclear underlying cause of symptoms
      • Older adults (e.g., > 60 years old) [14][18]

Patients > 60 years old with RLQ pain have a higher risk of serious underlying illness and should be evaluated thoroughly (e.g., with appropriate diagnostic imaging) irrespective of their appendicitis risk score. [14][18]

Moderate likelihood of appendicitis

High likelihood of appendicitis [19]

These tools use clinical findings and laboratory values to estimate the probability of acute appendicitis and can help inform management in adults. The pediatric appendicitis score can be applied in children. [9][10][11][12][16]

Appendicitis inflammatory response score (AIR Score) [9]

  • A relatively new scoring system that emphasizes laboratory parameters and graded clinical findings to provide a more objective clinical evaluation
  • Provides a more accurate estimated likelihood of acute appendicitis than the Alvarado scoring system [22]
Appendicitis inflammatory response score [23]
Characteristics Score
Symptoms Vomiting 1
RLQ pain 1
Physical examination Rebound tenderness Mild 1
Moderate 2
Strong 3
Temperature ≥ 38.5°C (101.3°F) 1
Laboratory parameters Leukocytosis 10,000/mm3–14,999/mm3 1
≥ 15,000/mm3 2
PMN 70–84% 1
≥ 85% 2
CRP 10–49 mg/L 1
≥ 50 mg/L 2
Likelihood of appendicitis
  • ≤ 4: Low
  • 5–8: Moderate
  • ≥ 9: High

Alvarado score (MANTRELS) [9][14][16][24][25]

  • A 10-point scoring system that uses eight parameters to estimate the likelihood of appendicitis
  • Accuracy is higher in young to middle-aged adults than in children < 10 years of age and adults > 60 years of age. [10] [24]
Alvarado score (MANTRELS) [26]
Characteristics Score
Symptoms Migration of pain to RLQ 1
Anorexia 1
Nausea and/or vomiting 1
Physical examination Tenderness in RLQ 2
Rebound pain 1
Elevated temperature > 37.3°C (99.1°F) 1
Laboratory parameters Leukocytosis (> 10,000/mm3) 2
Shift to the left (≥ 75% neutrophils) 1
Likelihood of appendicitis
  • ≤ 4: Low [16]
  • 5–6: Moderate
  • ≥ 7: High [16]

Acute appendicitis is usually a clinical diagnosis based on history, physical examination, and laboratory studies. Imaging is recommended if the clinical diagnosis is uncertain.

Laboratory studies [9][10]

A normal WBC count does not rule out acute appendicitis.

Imaging [9][10][13][19][27]

Decisions regarding the optimal timing and initial imaging modality should be based on individual patient factors (e.g., demographics, likelihood of appendicitis, risk of alternate diagnoses of concern, comorbidities), available resources, and local specialist preferences and hospital policy. [10][11][15][16]

  • Options for first-line imaging in nonpregnant adults [11][12]
    • CT abdomen [10][12][27]
      • Advantages: higher accuracy and reliability, allows operative planning, better evaluation of differential diagnoses (e.g., for patients > 60 years old)
      • Limitations: exposure to ionizing radiation and risk of contrast-related adverse events
    • Ultrasound abdomen (typically performed in conjunction with an appendicitis scoring system) [11][16]
      • Advantages: can limit the exposure to radiation and contrast, potentially reduce cost and length of stay (LOS) associated with CT use
      • Limitations: lower accuracy and reliability , can increase cost and LOS if CT abdomen is still required [13]
  • First-line imaging for pregnant adults and children: ultrasound abdomen [10][11][12]

The combined use of appendicitis risk scores and an initial ultrasound abdomen can reduce the need for CT abdomen in certain patients with suspected appendicitis, however, this should be balanced with the risk of missing the diagnosis. [11][16][17][28]

Abdominal ultrasound

Many institutions prefer ultrasound as the initial imaging modality, reserving CT scans for inconclusive ultrasound findings. [11][27]

While abdominal ultrasound can confirm the diagnosis of acute appendicitis, normal ultrasound findings do not reliably rule out appendicitis. [10]

CT abdomen with IV contrast

CT abdomen is the most accurate initial imaging modality for appendicitis. [10][12][27]

  • Supportive findings [27]
  • Additional considerations
    • Consider low-dose CT scan (with IV contrast) to minimize radiation exposure. [31][32]
    • Consider CT without contrast in patients with contrast allergy. [32]

MRI abdomen and pelvis [14][27][33]

  • Indications
    • MRI without IV contrast: pregnant patients with inconclusive ultrasound findings [27][33]
    • MRI with IV contrast: nonpregnant patients with inconclusive ultrasound findings and contraindications for CT scan
  • Findings: similar to CT scan findings

A normal MRI in a pregnant patient does completely not rule out the possibility of acute appendicitis. Consider diagnostic laparoscopy if clinical suspicion remains high. [11]

Diagnostic laparoscopy

Supportive care

Empiric antibiotic therapy for acute appendicitis [13][19][36][37]

Operative management

Appendectomy [13][14][19][33][41]

Appendectomy within 24 hours of diagnosis is the current standard of care for acute uncomplicated appendicitis. [11][11][33][41][42]

Surgery for acute uncomplicated appendicitis can safely be delayed for up to 24 hours from diagnosis.

Perform an emergency appendectomy for patients with complicated appendicitis and systemic symptoms. [11]

Initial operative treatment of appendiceal abscesses or appendiceal phlegmons is associated with a high risk of complications. [44]

Interval appendectomy [14][33][45][46][47]

Typically performed after a trial of nonoperative management for appendicitis.

  • Definition: appendectomy performed 6–8 weeks following the resolution of an acute episode of appendiceal mass or appendiceal abscess to minimize surgical complications [47]
  • Indications: currently not routinely recommended [14][45]
    • Consider for persistent or recurrent symptoms of appendicitis in a patient with an appendiceal mass or appendiceal abscess treated conservatively. [14][33][43]
    • Consider in patients > 40 years of age if there is concern for an underlying appendiceal tumor. [48][49]

Nonoperative management (NOM; conservative management) is typically preferred for patients at high risk of surgical morbidity if operated on immediately. It is sometimes followed by an interval appendectomy. NOM can also be offered to select patients with early uncomplicated appendicitis in consultation with an experienced surgeon, however, this remains an area of ongoing research. [11][12][33][45]

Indications [14][19][38][45]

Contraindications [33][38]

Steps of nonoperative management [19][38]

PAIN: Pain management, Antibiotics, Intravenous fluid therapy, and NPO are part of conservative management of appendicitis.

This checklist is applicable to patients with confirmed acute appendicitis and those with a high likelihood of appendicitis according to any of the risk stratification tools for acute appendicitis.

Right-sided carcinoma of the colon may manifest with clinical features similar to those of acute appendicitis. [55]

References:[54]

The differential diagnoses listed here are not exhaustive.

Inflammatory appendiceal mass (appendiceal phlegmon) [33][43]

Appendiceal abscess [19][33][43]

Gangrenous appendicitis

Perforated appendix [33]

Pylephlebitis [57]

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

Appendicitis in children [9][58]

  • Clinical features
    • The reliability of signs and symptoms in children is lower.
    • Most reliable symptoms: emesis and duration of pain, abdominal tenderness and pain with walking, jumping, and coughing
  • Diagnostics [11]
Pediatric appendicitis score [59]
Characteristics Score
Symptoms Migration of pain to RLQ 1
Anorexia 1
Nausea/vomiting 1
Physical examination RLQ tenderness 2
RLQ pain elicited on coughing/jumping/percussion 2
Temperature ≥ 38°C (100.4°F) 1
Laboratory parameters Leukocytosis (≥ 10,000/mm3) 1
PMN ≥ 75% 1

Likelihood of appendicitis [15]

  • ≤ 3: Low
  • 4–6: Moderate
  • ≥ 7: High

The diagnosis should not be based solely on the clinical score in children. [11]

Appendicitis in pregnant individuals [9][61]

Appendicitis in patients > 60 years of age [14][18][20][52][62]

  • Clinical features
  • Diagnostics: Imaging should be considered regardless of the scores. [14]
  • Complications: Older patients are more likely to develop complications, especially perforated appendix. [14]

Individuals > 60 years of age have a higher risk of perforation! [14]

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