• Clinical science

Acute appendicitis


Appendicitis refers to acute inflammation of the appendix, and is the most common cause of acute abdomen requiring emergency surgery. It typically presents with periumbilical pain, which migrates to the right lower quadrant (RLQ), associated with fever, vomiting, anorexia, and malaise. While appendicitis is primarily a clinical diagnosis, raised inflammatory markers and imaging may be useful. The most crucial aspect of treatment is timely intervention (laparoscopic or conventional open appendectomy) to prevent progression to perforation and sepsis, as well as antibiotics.


Inflammation of the vermiform appendix, a vestigial structure (also referred to as the cecal appendix or vermiform process).



Epidemiological data refers to the US, unless otherwise specified.




  • Early: mucosal hyperemia with edema and ulceration due to obstruction of the appendix; reversible phase
  • Suppurative: transmural spread of infection within the appendix
  • Gangrenous: diffuse inflammatory changes in the entire appendiceal wall produce intramural arterial (and venous) thromboses; leading to ischemia, necrosis, and, eventually, a gangrenous appendix
  • Perforated
    • Persistently rising intraluminal pressure results in perforation of the gangrenous portion of the appendix.
    • Phlegmonous appendicitis; possibly periappendiceal abscess
    • Complete perforation with multiple abdominal quadrant sepsis and generalized peritonitis
  • Spontaneously resolving: relief of symptoms once the cause of obstruction is spontaneously expelled from the appendiceal lumen
  • Recurrent appendicitis: repeated episodes of RLQ pain; inflamed appendix histopathologically confirmed after appendectomy
  • Chronic appendicitis: persistent RLQ for at least a 3-week duration, with no other possible cause identifiable; relief of symptoms post-appendectomy and histopathological confirmation of appendicitis


Clinical features

The key symptom in appendicitis is right lower quadrant pain!References:[4][2][3]


  • 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:[4][2][3]


Physiological structure of the vermiform appendix

  • Length: ∼ 2–20 cm (average ∼ 7 cm)
  • Diameter: < 6–8 mm (average ∼ 5 mm)
  • Layers from inside to outside:
    • Lumen → single layered high columnar epitheliumlamina propria mucosa with numerous lymphoid tissue → lamina muscularis mucosa → submucosa → stratum circulare muscularis (circular muscle layer) → stratum longitudinale muscularis (longitudinal muscle layer) → serosa

Changes in appendicitis

  • Infiltration of the tissue with leukocytic granulocytes
  • Depending on the stage of pathology, possible ulceration and wall necrosis

Differential diagnoses

Colon cancer in the elderly may mimic acute appendicitis!References:[6][7]

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



Gangrenous perforation (10% of cases)


  • Periappendiceal abscess
    • Definition: abscess involving the area around the appendix as a result of a concealed perforation
    • Clinical features
      • Patients typically present after 5 days with high fever, abdominal pain, and abdominal edema (if there is involvement of the abdominal wall).
      • Normal abdominal examination may be unrevealing.
    • Diagnosis: CT scan
    • Management
      • Small abscess → bowel rest, IV antibiotic therapy followed by interval appendectomy after 6–8 weeks
      • Larger abscesspercutaneous drainage with catheter and bowel rest, IV antibiotic therapy
        • When the fistula from the catheter closes → interval appendectomy
      • Multicompartmental abscess → prompt surgical drainage


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


  • Uncomplicated appendicitis with adequate management (surgical intervention) has an excellent prognosis.
  • Perforation and peritonitis: ∼ 1% mortality
  • Up to 20% of patients are found to have a normal appendix following surgery.
  • Elderly patients (> 60 years old) have a poorer prognosis.


Special patient groups

Appendicitis in children

  • Children are rarely able to localize the origin of their pain.
  • Indirect signs: bending the right hip joint in supine position, weakened abdominal wall reflexes in the RLQ, reduced abdominal breathing

Appendicitis in pregnancy

  • Atypical (higher) pain localization: As the uterus expands during pregnancy, the appendix may be pushed up into the RUQ of the abdomen. The position of the appendix may shift in this case, and the typical RLQ pain may not be present.
  • Perforated appendix is associated with higher risk of fetal loss.
  • Ultrasound is diagnostic procedure of choice

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

Appendicitis in older patients

  • Chronic and atypical history
  • Pressure (instead of pain) in right iliac fossa
  • Low-grade fever (not always present)
  • Confusion
  • Subtle abdominal guarding
  • Reduced sensitivity to pressure point tests