Acute appendicitis

Pathophysiology & Presentation - The Angry Worm

• Pathogenesis: Luminal obstruction (fecalith, lymphoid hyperplasia) → mucus buildup → ↑ intraluminal pressure → bacterial overgrowth (E. coli, Bacteroides).
• Progression: Inflammation → venous congestion → ischemia → necrosis → perforation (< 24-48 hrs).

• Classic Symptoms:
  • Early: Vague, dull periumbilical pain (visceral).
  • Followed by: Anorexia (the "hamburger sign"), nausea, and vomiting.
  • Late: Pain migrates to the Right Lower Quadrant (RLQ), becoming sharp and localized (somatic).
• Key Signs:
  • Tenderness at McBurney's point.
  • Low-grade fever (~38°C / 100.4°F).
  • Peritoneal signs: Rovsing's, Psoas, Obturator.

⭐ Exam Tip: The migration of pain from the periumbilical area to the RLQ is the most reliable clinical feature.

Diagnosis & Scoring - The Scorecard

• Alvarado Score: A 10-point clinical scale to stratify risk and guide management.

  • 📌 Mnemonic: MANTRELS
  • Migratory RLQ pain (1)
  • Anorexia (1)
  • Nausea/Vomiting (1)
  • Tenderness in RLQ (2)
  • Rebound tenderness (1)
  • Elevated temp >37.3°C (1)
  • Leukocytosis >10,000/mm³ (2)
  • Shift to left-bandemia (1)

• Score-Based Triage Pathway:

• Imaging Confirmation:
  • CT scan (IV contrast): Gold standard in adults. Shows dilated appendix (>6mm), wall enhancement, periappendiceal fat stranding.
  • Ultrasound: Preferred for children and pregnant patients to avoid radiation.

⭐ A normal white blood cell count does not exclude appendicitis. Up to 20% of patients with surgically confirmed appendicitis present with a WBC within the normal range.

Imaging & Differentials - Picture Perfect?

• Imaging Modalities:
  • CT Scan (A/P with IV contrast): Preferred for most adults.
    • Key signs: Appendix >6 mm diameter, wall thickening, periappendiceal fat stranding, appendicolith.
  • Ultrasound: Initial choice for children and pregnant women.
    • Key signs: Non-compressible, blind-ended tube >6 mm; "target sign" on transverse view.
  • MRI: Alternative in pregnancy if ultrasound is equivocal.

• Common Differentials:
  • GI: Meckel's diverticulitis, Crohn's ileitis, mesenteric adenitis.
  • Gyn (📌 METRO): Meckel's, Ectopic pregnancy, Tubo-ovarian abscess, Ruptured cyst, Ovarian torsion.
  • GU: Ureteral colic, pyelonephritis.

⭐ CT scanning has dramatically reduced the negative appendectomy rate (perforating a normal appendix) from ~20% to <5%.

Management & Complications - Snip, Snip, Troubles

• Pre-operative Care: NPO, IV fluids, and broad-spectrum IV antibiotics (e.g., Cefoxitin, Piperacillin-tazobactam) to cover gram-negatives and anaerobes.
• Definitive Treatment: Laparoscopic appendectomy is the gold standard.

• Complications:
  • Perforation: Most common complication, leading to peritonitis.
  • Appendiceal Abscess: Contained infection; requires drainage.
  • Phlegmon: Inflammatory mass without a drainable pus collection.
  • Surgical Site Infection (SSI).

⭐ Appendiceal Mass (Phlegmon/Abscess): If a patient presents late with a contained perforation forming a palpable mass, the initial management is conservative with IV antibiotics and possibly percutaneous drainage. An interval appendectomy is performed 6-8 weeks later.

High‑Yield Points - ⚡ Biggest Takeaways

• Classic presentation is periumbilical pain migrating to the RLQ (McBurney's point).
• Key physical exam findings include Rovsing's, psoas, and obturator signs.
• Caused by luminal obstruction, most commonly by a fecalith.
• Diagnosis is clinical; CT scan is the most accurate imaging in adults.
• Ultrasound is the preferred initial imaging for children and pregnant patients.
• Definitive treatment is surgical appendectomy.
• The most feared complication is perforation, leading to peritonitis or abscess.