• Clinical science

Acute appendicitis

Summary

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.

Definition

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

Epidemiology

  • Common cause of acute abdomen
  • Lifetime risk: ∼ 8%
  • Peak incidence: 10–19 years of age

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Obstruction of appendiceal lumen by:
    • Lymphoid tissue hyperplasia (60% of cases)
    • Fecalith (35% of cases)
    • Less common: foreign bodies, worm infestations, intestinal infections, tumors (e.g., carcinoid tumor), hemolytic diseases
  • Stasis of mucus and fluid → bacterial growth and local inflammation → rising intraluminal pressure → vascular compromise → ischemianecrosis → perforation and peritonitis

References:[3][4]

Pathophysiology

  • 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

References:[5]

Clinical features

  • Nonspecific symptoms
  • Abdominal pain: classical presentation
    • Initially, dull migratory periumbilical pain (due to visceral peritoneum irritation)
    • After 4–24 hours, sharp RLQ pain; (due to parietal peritoneum irritation by a distended and inflamed appendix) with rebound tenderness
  • Signs of appendicitis
    • Blumberg's sign: rebound tenderness caused upon suddenly ceasing deep palpation of the RLQ
    • McBurney point tenderness: an area one-third of the distance from the right anterior superior iliac spine to the umbilicus (in the RLQ)
    • Rovsing's sign: deep palpation of the LLQ causes RLQ referred pain
    • Psoas sign: RLQ pain with extension of the right leg against resistance (secondary to inflammation of a retrocecal appendix)
    • Obturator sign: RLQ pain with flexion and internal rotation of the right leg
    • Pain in the Pouch of Douglas: pain elicited by palpating the recto-uterine pouch on rectal examination
    • Baldwin's sign: pain in the flank area when bending the right leg (suggests an inflammed retrocecal appendix)
    • Sherren's triangle: a virtual triangle on the anterior abdominal wall between the anterior superior iliac spine, umbilicus, and symphysis pubis. There are various tender pressure points (areas of hyperesthesia) within this triangle if appendicitis is involved.
    • Lanz's point: an area between the right and middle third of the distance between both iliac spines

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

Diagnostics

  • 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]

Pathology

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.

Treatment

General approach

Appendectomy

Suspected appendicitis warrants surgical intervention!

  • Surgical approach may be laparoscopic or open and is decided on a case-by-case basis
  • Laparoscopic approach
    • Insert the trocars (usually three at most).
    • Perform a diagnostic laparoscopy.
    • Identify the appendix.
    • Prepare the appendiceal base by ligating the mesenteric vessels.
    • Ligate the appendiceal base (e.g., using Roeder's Knot) and resect the appendix.
    • Retrieve the appendix (using an extraction bag).
    • Close the abdominal wall.
  • Open approach

References:[3][8]

Complications

Gangrenous perforation (10% of cases)

  • Perforation may have occurred prior to reduced pain perception.
  • Clinical features
    • Persistent clinical symptoms lasting longer than 24 hours; signs of sepsis
    • Features of peritonism (rebound tenderness, guarding, rigidity); aggravated by light stimulation/movement
  • Treatment

Abscess

Postoperative complications

  • Abdominal wall abscess
  • Mechanical or paralytic ileus
  • Appendiceal stump leak

References:[8][9][5]

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

Prognosis

  • 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.

References:[5][4]

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

References:[8][9][10]