MD Notes

creation date: 2026-04-05 23:30
tags: Pathologies

Appendicitis

Background

Definitions

Appendicitis is the inflammation of the appendix. It is a common cause of acute abdomen.

Pathogenesis

The classic history of appendicitis is thought to be similar to other inflammatory processes involving hollow visceral organs.

Luminal obstruction and inflammation
Fecaliths, calculi, or tissue hyperplasia/neoplasm can block the appendix. In endemic areas, parasites (particularly Ascaris lumbricoides) can also cause obstruction. This results in the lumen of the appendix filling up with mucus.

Ischemia, necrosis, and infection
When the lumen distends, luminal and intramural pressure increases. This results in thrombosis and occlusion of the small vessels, and stasis of lymphatic flow. This causes ischemia and then necrosis.

Engorgement of the appendix also stimulates the afferent nerves entering at T8-T10, leading to central/periumbilical abdominal pain.

As the appendix worsens, bacterial overgrowth occurs, initially aerobic followed by a mix of aerobic and anaerobic later in disease course. Common organisms include:

  • Escherichia coli
  • Peptostreptococcus
  • Bacteroides fragilis
  • Pseudomonas sp.

Bacteria invade the appendiceal wall and causes an influx of neutrophils. This inflammation irritates the parietal peritoneum resulting in somatic pain signals localized to the right lower quadrant.

Perforation
After more than 24 hours, the diseased appendix can perforate, resulting in localized abscess formation or diffuse peritonitis.

Clinical Presentation

Signs & Symptoms

Classic symptoms are:

  • Right lower quadrant abdominal pain
  • Anorexia
  • Nausea and vomiting

Pain typically begins periumbilical which migrates to the RLQ as the disease progresses. Later in the course, the patient may present with fever.

Other atypical features (which are more common in immunosuppressed patients) include:

  • Indigestion
  • Flatulence
  • Bowel irregularity
  • Diarrhea
  • Generalized malaise

Classic signs found on physical exams include:

  • McBurney’s point tenderness (1/3 from anterior superior iliac spine to umbilicus; sn 70%, sp 80%)
  • Rovsing’s sign (referred pain in LLQ when rebound RLQ; sn 40%, sp 80%)
  • Psoas sign (RLQ pain with passive right hip extension; sn 25%, sp 90%)
  • Obturator sign (RLQ pain with right hip and knee flexion then internal rotation of hip; sn 8% sp 94%)

History & Physical Exam

A quick history of characteristic abdominal pain with positive sign(s) is sufficient for further workup.

Minimal time should be spent as appendicitis is an emergency.

Risk Factors

Diagnosis

Criteria

Definitive diagnosis is made histologically through a surgical specimen. A presumptive diagnosis is often made based on characteristic clinical findings.

Work-up

Once clinical suspicion is established the following are performed to evaluate.
Laboratory tests
Tests include:

  • WBC count with differential
  • Serum CRP
  • Pregnancy test

An elevated WBC (>10x10^9/L) and/or elevated CRP (>10) supports a diagnosis of appendicitis.

Imaging
Contrast CT of the abdomen pelvis is first-line for suspected appendicitis. If unavailable or should be avoided (eg. pregnant or pediatric), ultrasound is reasonable.

CT findings:

  • Enlarged appendiceal double-wall thickness (>6 mm)
  • Appendiceal wall thickening (>2 mm)
  • Periappendiceal fat stranding
  • Appendiceal wall enhancement
  • Appendicolith

Ultrasound findings:

  • Noncompressible appendix with double-wall thickness diameter >6 mm
  • Focal pain over appendix with compression
  • Appendicolith
  • Increased echogenicity of inflamed periappendiceal fat
  • Fluid in RLQ

Differential

A number of conditions involving the RLQ can mimic signs and symptoms of acute appendicitis.

  • Cecal diverticulitis (more common in Eastern populations; eval: CT)
  • Meckel’s diverticulitis
  • Acute ileitis (self-limited bacterial infection, consider if diarrhea is prominent symptom)
  • Crohn’s disease
  • Gynecologic/obstetrical conditions (PID, ruptured ovarian cyst, ovarian torsion, endometriosis, ectopic pregnancy); eval: pelvic U/S
  • Urologic conditions (renal colic, testicular torsion, epididymitis)

Red Flags / Complications

Delayed treatment can result in perforation. Mortality of appendicitis is generally low.

Management

Non-Perforated Appendicitis

For a non-perforated appendix, also referred to as simple/uncomplicated appendicitis, both nonoperative management and appendectomy can be considered.

Nonoperative management
Nonoperative management is appropriate for patients without findings of diffuse peritonitis or imaging evidence of large abscess, phlegmon, perforation, or tumour.

Evidence suggests nonoperative management is not inferior to appendectomy and may be preferred due to faster recovery. However, there is a risk of recurrence of appendicitis (approximately 30% risk).

Relative contraindications include appendicolith and age ≥45 due to delayed response to antibiotics. Contraindications include diffuse peritonitis, hemodynamic instability, severe sepsis, pregnancy, immunocompromised status, or history of IBD.

Treatment is not standardized but consist of initial IV antibiotics followed by oral antibiotics.

Appendectomy
Appendectomy can be performed open or laparoscopically. Prior to surgery, patients require:

  • IV fluids
  • Correction of electrolyte abnormalities
  • Pain control
  • Prophylactic antibiotics

Perforated Appendicitis

Unstable patients or free perforation
Emergency appendectomy and drainage and irrigation of the peritoneal cavity is indicated.

Stable patients
Patients may have either immediate appendectomy or initial nonoperative management.

Initial nonoperative management consist of:

  • Antibiotics (eg. pip-tazo, or ceftriaxone and metronidazole)
  • IV fluids
  • Bowel rest

References

Tools / Guidelines

Additional Reading