Ch23: Acute Appendicitis（急性阑尾炎）

Preparatory Mindset

Acute appendicitis is the most common surgical emergency — every medical student must master the presentation, the pain migration, the signs, and the management (appendectomy ± antibiotics). The lecture (Jingge Yang, 7.5KB) covers the pathology (simple → suppurative → gangrenous → perforation), the classic pain migration (periumbilical → right iliac fossa), McBurney's point, complications of appendectomy, and the differentials.

Exam mindset: the visceral-to-somatic pain migration (64% sensitive, 82% specific), the clinical signs (McBurney, Rovsing, psoas, obturator), the Alvarado/appendicitis score, and the management (laparoscopic appendectomy; interval appendectomy for appendix mass). Links to Anatomy (Ch18: appendix positions, McBurney point, appendicular end artery) and Imaging (CT/US).

Core Concepts

1. Anatomy recap (MUST KNOW)

• Appendix: vermiform, base at the convergence of the three teniae coli; McBurney's point = one-third of the line from the umbilicus to the ASIS (just below the middle of the line)
• Positions (variable): retrocecal (most common), pelvic, subcecal, pre/post-ileal, paracolic — position explains atypical pain (retrocecal → right flank; pelvic → suprapubic)
• Blood supply: appendicular artery (end artery from ileocolic/SMA) — obstruction → ischemia → necrosis → perforation
• Nerve supply: visceral (T10 → periumbilical pain) & parietal (somatic → RIF pain when inflamed peritoneum involved)

2. Pathogenesis & pathology (MUST KNOW)

• Cause: luminal obstruction (fecalith/lymphoid hyperplasia — young adults, tumor) → ↑ pressure → venous congestion → ischemia → bacterial overgrowth (gut flora) → inflammation → gangrene → perforation
• Pathologic stages: simple (catarrhal) → suppurative → gangrenous → perforated (+ abscess or diffuse peritonitis)
• Complications of appendicitis: perforation with diffuse peritonitis, appendix mass/abscess (walled-off), pylephlebitis (septic portal vein thrombosis — rare but dangerous), wound infection
• Epidemiology: peak 10-30 years; lifelong risk ~7-8%; F:M slightly more in adults, M>F in children

3. Clinical features (MUST KNOW)

1. Initial: vague periumbilical or epigastric pain (visceral, T10 — from distension) — colicky/dull 2. Migration to the right iliac fossa (RIF) within 6-24 h as the parietal peritoneum becomes inflamed (somatic) — the classic migration (64% sensitive, 82% specific) 3. Anorexia (very common), nausea/vomiting (usually after pain starts), low-grade fever, constipation or diarrhea (pelvic appendix)

- McBurney's point tenderness (RIF, deep palpation) - Rovsing's sign: palpation of the left iliac fossa causes pain in the RIF (referred — colonic gas shifts to the cecum) - Psoas sign: pain on passive extension of the right hip (retrocecal appendix on psoas) - Obturator sign: pain on internal rotation of the flexed right hip (pelvic appendix on obturator internus) - Guarding/rigidity/rebound (peritonism — perforation/advanced) - Fever (usually <38.5°C; higher with perforation), tachycardia - Rectal examination: tenderness on the right (pelvic appendix)

• Classic history:
• Atypical presentations: retrocecal (right flank/loin pain, psoas irritation), pelvic (suprapubic pain, urinary/rectal symptoms, pelvic tenderness on rectal exam), retroileal
• Signs (MUST KNOW):
• "Normal" temperature/leukocytosis do NOT exclude appendicitis

4. Investigations (MUST KNOW)

- Ultrasound: first-line in children & pregnancy — non-compressible, thickened (>6 mm) blind-ending appendix, target sign, periappendiceal fluid; operator-dependent; limited in perforation/obesity - CT abdomen (with contrast): the most sensitive test — dilated thick-walled appendix (>6 mm), periappendiceal fat stranding, fecalith, abscess; definitive in equivocal/adult cases - MRI: pregnant patients (no radiation)

• Bloods: leukocytosis with neutrophilia (WBC 10-18), CRP ↑; urinalysis (exclude UTI/renal colic — pyuria can occur with inflamed pelvic appendix); β-hCG (women — ectopic); LFTs/amylase (differentials)
• Imaging:
• Scores: Alvarado (MANTRELS) score & Appendicitis Inflammatory Response (AIR) score — stratify risk (low → observe/discharge, intermediate → imaging, high → surgery)
• Diagnosis is CLINICAL first — imaging for equivocal cases; "a normal appendix on CT reliably excludes"

5. Differential diagnosis (MUST KNOW)

• GI: mesenteric adenitis (children), gastroenteritis, IBD (Crohn's), Meckel's diverticulitis, intussusception, diverticulitis (cecal), constipation
• GYN (women of childbearing age): ectopic pregnancy (β-hCG), ovarian cyst torsion/rupture, PID/salpingitis, endometriosis, Mittelschmerz
• GU: ureteric colic/renal stone, UTI/pyelonephritis, testicular torsion (referred)
• Other: cholecystitis, pancreatitis, perforated ulcer, right basal pneumonia (children), psoas abscess
• Key exam questions: β-hCG in all women; urine; consider CT/US; gynecologic review

6. Management (MUST KNOW)

- Conservative: IV antibiotics + percutaneous drainage (abscess) → interval appendectomy in 6-12 weeks (elective) - Immediate surgery only if: failure of conservative therapy, diffuse peritonitis, deterioration

• Acute appendicitis (uncomplicated): appendectomy — laparoscopic (preferred — less pain, faster recovery, better diagnosis) or open (McBurney/gridiron incision)
• Antibiotics: perioperative prophylaxis (cefazolin + metronidazole); for uncomplicated appendicitis, some trials support antibiotics alone (APPAC/CODA) — but appendectomy remains standard; perforated/gangrenous: therapeutic antibiotics (4-7 days)
• Appendix mass/abscess (walled-off, presents day 3-5):
• Perforated appendicitis with diffuse peritonitis: emergency appendectomy + lavage + antibiotics
• Pregnancy: appendectomy is safe (laparoscopic in 1st/2nd trimester; open preferred near term); fetal loss risk ↑ with perforation
• Complications of appendectomy: wound infection (most common), intra-abdominal abscess (post-op fever day 5-7 → CT → drain), ileus, bleeding, stump leak, infertility (historical, from severe PID-like sepsis — rare now), hernia (open incision)

High-Yield Points

• Classic: periumbilical pain → migrates to RIF (visceral T10 → somatic parietal); anorexia; fever
• McBurney's point = 1/3 of the line umbilicus→ASIS (just below the middle)
• Signs: McBurney tenderness, Rovsing (LIF → RIF pain), psoas (retrocecal), obturator (pelvic)
• CT = most sensitive; US first-line in children/pregnancy; MRI in pregnancy
• Alvarado score stratifies; β-hCG in all women (ectopic)
• Retrocecal = most common position (right flank pain); pelvic → suprapubic/rectal signs
• Appendicular artery = end artery → obstruction → ischemia → perforation
• Management: laparoscopic appendectomy; antibiotics for uncomplicated (trial); mass/abscess → conservative + interval appendectomy; perforation → emergency + antibiotics
• Complications: wound infection (most common), abscess (post-op fever → CT → drain)
• Differentials: mesenteric adenitis, Crohn's, ectopic, ovarian torsion, renal colic, pneumonia

Topic Summary

Acute appendicitis = most common surgical emergency. Cause: luminal obstruction (fecalith) → ischemia → inflammation → gangrene → perforation. Classic presentation: periumbilical pain migrating to the RIF (visceral→somatic), anorexia, nausea, low-grade fever; signs = McBurney tenderness, Rovsing, psoas (retrocecal), obturator (pelvic); retrocecal (most common position) → flank pain. Diagnosis: clinical first; WBC/CRP; US (children/pregnancy) or CT (adults — most sensitive); MRI in pregnancy; Alvarado score; exclude ectopic (β-hCG), ovarian torsion, renal colic, mesenteric adenitis, Crohn's. Management: appendectomy (laparoscopic preferred) + antibiotics; appendix mass/abscess → conservative + interval appendectomy; perforation → emergency surgery. Complications: wound infection (most common), intra-abdominal abscess (post-op fever → CT → drain).