Acute Appendicitis and Peritonitis¶
Chapter 342 | Part 10: Disorders of the Gastrointestinal System
KEY CLINICAL POINTS¶
- Acute appendicitis is the most common acute surgical emergency, with ~10–11 cases per 10,000 annually, peaking in 10–19-year-olds.
- Perforation risk is ~10–20%, higher in patients <5 or >65 years, with mortality <1% due to improved care but remains ~3–15% in complicated cases.
- Clinical diagnosis is challenging due to overlapping mimics (e.g., diverticulitis, ovarian torsion) and atypical presentations in children/elderly.
- CT imaging (sensitivity 86%, specificity 81%) is preferred for uncertain cases, while ultrasound is useful in women for pelvic appendicitis.
- Nonoperative management is viable for uncomplicated appendicitis, but surgery remains the standard for perforated cases or abscesses.
1. DEFINITION & OVERVIEW¶
Acute appendicitis is inflammation of the vermiform appendix, often leading to perforation. Peritonitis refers to inflammation of the peritoneum, either infectious (secondary) or noninfectious (aseptic).
Table 342-1: Conditions Mimicking Appendicitis¶
| Condition |
|---|
| Crohn’s disease |
| Cholecystitis or gallbladder disease |
| COVID-19 infection |
| Diverticulitis |
| Ectopic pregnancy |
| Endometriosis |
| Gastroenteritis or colitis |
| Gastric/duodenal ulceration |
| Hepatitis |
| Kidney disease (nephrolithiasis) |
| Liver abscess |
| Meckel’s diverticulitis |
| Mittelschmerz |
| Mesenteric adenitis |
| Condition |
|---|
| Omental torsion |
| Pancreatitis |
| Lower lobe pneumonia |
| Pelvic inflammatory disease |
| Ruptured ovarian cyst |
| Small-bowel obstruction |
| Urinary tract infection |
1.1 Epidemiology¶
Incidence: ~10–11 per 10,000 annually; peaks in 10–19-year-olds. Global incidence increasing, but mortality from complications decreasing. Risk factors include socioeconomic status, age (<5 or >65 years), and appendiceal tumors.
1.2 Pathogenesis¶
Obstruction of the appendiceal lumen (fecaliths, lymphoid hyperplasia) leads to bacterial overgrowth, ischemia, and perforation. Nonoperative management may resolve uncomplicated cases.
2. EPIDEMIOLOGY¶
Global incidence increasing, but mortality from complications decreasing. Risk factors include socioeconomic status (lower risk in higher SES), age (<5 or >65 years), and appendiceal tumors. Perforation risk ~10–20%.
2.1 Demographics¶
Peak incidence in 10–19-year-olds; increasing global incidence. Mortality <1% for uncomplicated cases, but ~3–15% in complicated cases (e.g., elderly).
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Obstruction of the appendiceal lumen (fecaliths, lymphoid hyperplasia) leads to bacterial overgrowth, ischemia, and perforation. Aseptic peritonitis caused by chemical irritation from gastric/bile/pancreatic fluids.
Table 342-5: Conditions Leading to Secondary Bacterial Peritonitis¶
| Condition |
|---|
| Bowel perforation |
| Appendicitis |
| Anastomotic leakage |
| Adhesion |
| Diverticulitis |
| Iatrogenic (endoscopic perforation) |
| Ingested foreign body |
| Inflammation |
| Condition |
|---|
| Intussusception |
| Neoplasms |
| Obstruction |
| Peptic ulcer disease |
| Strangulated hernia |
| Vascular (ischemia/embolus) |
| Trauma (blunt/penetrating) |
| Perforation/leakage of other organs |
| Biliary leakage (post-liver biopsy) |
| Cholecystitis |
| Intraperitoneal bleeding |
| Pancreatitis |
| Salpingitis |
| Urinary bladder |
| Loss of peritoneal integrity |
| Intraperitoneal chemotherapy |
| Iatrogenic (postoperative foreign body) |
| Perinephric abscess |
| Peritoneal dialysis/indwelling devices |
| Trauma |
3.1 Mechanisms¶
Fecaliths (50% of perforated cases) or intraluminal scarring cause obstruction. Ischemia leads to perforation, with risk of portal vein thrombosis and abscesses in severe cases.
4. CLINICAL FEATURES¶
Classic presentation includes migratory pain to the right lower quadrant, rebound tenderness, and fever. Atypical presentations in children/elderly may lack typical symptoms.
Table 342-2: Common Presenting Symptoms¶
| Symptom | Frequency |
|---|---|
| Abdominal pain | >95% |
| Anorexia | >70% |
| Constipation | 4–16% |
| Diarrhea | 4–16% |
| Fever | 10–20% |
| Nausea | >65% |
| Vomiting | 50–75% |
Table 342-3: Presenting Signs¶
| Sign | Frequency |
|---|---|
| Abdominal tenderness | >95% |
| Right lower quadrant tenderness | >90% |
| Rebound tenderness | 30–70% |
| Rectal tenderness | 30–40% |
| Cervical motion tenderness | 30% |
| Rigidity | ~10% |
| Psoas sign | 3–5% |
| Obturator sign | 5–10% |
| Rovsing’s sign | 5% |
| Palpable mass | <5% |
4.1 Symptoms¶
Abdominal pain (95% frequency), anorexia (70%), nausea/vomiting (65–75%), constipation (4–16%), diarrhea (4–16%), fever (10–20%).
4.2 Signs¶
Abdominal tenderness (>95%), right lower quadrant tenderness (>90%), rebound tenderness (30–70%), rectal tenderness (30–40%), cervical motion tenderness (30%).
5. DIFFERENTIAL DIAGNOSIS¶
Conditions mimicking appendicitis include diverticulitis, ovarian torsion, pelvic inflammatory disease, and mesenteric adenitis. Atypical presentations in children/elderly require careful evaluation.
5.1 Mimicking Conditions¶
See Table 342-1 for conditions requiring differentiation (e.g., ectopic pregnancy, urinary tract infections, and gynecological pathologies).
6. INVESTIGATIONS & DIAGNOSIS¶
Laboratory tests show leukocytosis (10,000–18,000 cells/ µ L) with left shift. CT imaging (sensitivity 86%, specificity 81%) is preferred for uncertain cases. Ultrasound is useful in women for pelvic appendicitis.
Table 342-4: Classic Signs of Appendicitis¶
| Maneuver | Findings |
|---|---|
| Rovsing’s sign | Palpating left lower quadrant causes pain in right lower quadrant |
| Obturator sign | Internal hip rotation causes pain (pelvic appendicitis) |
| Iliopsoas sign | Right hip extension causes pain (retrocecal appendicitis) |
6.1 Diagnostic Criteria¶
CT findings: appendiceal wall thickening (>6 mm), luminal distension, fatty stranding, or air around the appendix. Free air indicates perforation.
7. MANAGEMENT & TREATMENT¶
Uncomplicated appendicitis may be managed nonoperatively, but surgery is standard for perforated cases. Laparoscopic appendectomy is preferred for minimally invasive recovery.
7.1 Surgical Options¶
Laparoscopic appendectomy (preferred) or open appendectomy. Nonoperative management for uncomplicated cases with delayed surgery (6–12 weeks).
7.2 Complicated Cases¶
Abscesses (>3 cm) require drainage and antibiotics. Perforated cases need urgent surgery with peritoneal lavage.
8. PROGNOSIS & COMPLICATIONS¶
Mortality <1% for uncomplicated cases, but ~3–15% in complicated cases (especially elderly). Complications include abscesses, sepsis, and portal vein thrombosis.
8.1 Risk Factors¶
Age >65 years, delayed diagnosis, and comorbidities increase mortality. Perforation risk ~10–20%.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Appendix may shift to right upper quadrant; appendicitis is the most common surgical emergency. Children: Atypical presentations; smaller omentum may fail to contain perforation. Elderly: Subtle symptoms, higher mortality.
9.1 Pregnancy¶
Appendix may be displaced by uterus; fetal mortality risk increases 4x with perforation (5–20%).
10. KEY POINTS & CLINICAL PEARLS¶
- Appendicitis is the most common acute surgical emergency. 2. CT is preferred for uncertain diagnosis. 3. Nonoperative management viable for uncomplicated cases. 4. Perforation risk ~10–20%, higher in extremes of age. 5. Atypical presentations in children/elderly require careful evaluation.