Acute Appendicitis and Peritonitis¶
Chapter 342 | Part 10: Disorders of the Gastrointestinal System · Part 10 – Gastrointestinal Disorders · Chapter 342
Key Clinical Points¶
- Acute appendicitis is the most common acute general surgery emergency affecting the abdomen (incidence ~10–11 cases per 10,000 people annually).
- Risk of perforation is ~10–20%, with a significantly higher risk in patients ≥65 years old.
- Clinical hallmark: Migration of pain to the right lower quadrant over 12–24 h; absence of anorexia should prompt a reconsideration of the diagnosis.
- Imaging: CT has high sensitivity (≥0.94) and specificity (0.95); Ultrasound is highly useful for identifying pelvic pathology in women.
- Mortality: Uncomplicated appendicitis (0.1–0.5%); Perforated appendicitis (3% overall, up to 15% in elderly).
- Fetal mortality in pregnancy increases fourfold (from 5% to 20%) if perforation occurs.
- Abscess management (>3 cm): Broad-spectrum antibiotics + percutaneous drainage → interval appendectomy in 6–12 weeks.
- Secondary peritonitis most commonly results from perforation of the appendix, colonic diverticula, or the stomach/duodenum.
- Diagnostic criteria for CT: Appendiceal diameter >6 mm, wall thickening, and fatty tissue stranding.
- Anatomical variation is significant; the appendix can be located in various positions (e.g., retrocecal, pelvic) affecting clinical presentation.
DEFINITION & OVERVIEW¶
• Definition: Acute appendicitis is the most common acute general surgery emergency affecting the abdomen. • Pathophysiology: ◦ Obstruction of the appendiceal lumen → bacterial overgrowth and luminal distension. ◦ Increased intraluminal pressure → inhibited flow of lymph and blood → vascular thrombosis and ischemic necrosis. ◦ Progression: Inflammation → gangrenous necrosis → perforation (may be contained by omentum or other tissues to form an abscess). ◦ Fecaliths: Found in ~50% of patients with gangrenous appendicitis who perforate; rarely identified in those with simpler disease. ◦ Note: Perforation near the base of the appendix should raise concerns about another disease process.
EPIDEMIOLOGY¶
• Incidence: ~10–11 cases per 10,000 people annually. ◦ Affects biological males and females equally. ◦ Most common in 10- to 19-year-olds (though average age at diagnosis is increasing). • Risk Factors: ◦ Perforation: ~10–20% risk; significantly higher in patients ≥65 years old. ◦ Socioeconomic status: Higher socioeconomic status associated with lower risk of appendicitis with or without perforation. ◦ Appendiceal tumors: Incidence appears to be increasing.
ETIOLOGY & PATHOPHYSIOLOGY¶
• Etiology: Not fully understood; factors include fecaliths, incompletely digested food residue, lymphoid hyperplasia, intraluminal scarring, tumors, bacteria, viruses, and inflammatory bowel disease. ◦ Obstruction of the appendiceal lumen is believed to be an important step in development.
CLINICAL FEATURES¶
• General Presentation: Patients with simple appendicitis are often only mildly ill. Temperature >38.3°C (~101°F) and rigors suggest complications (perforation, phlegmon, or abscess). ◦ Nausea usually follows the development of abdominal pain (distinguishes from gastroenteritis). ◦ Anorexia is highly common; its absence should prompt a reconsideration of the diagnosis. • Symptoms (Table 342-2): ◦ Abdominal pain: >95% ◦ Anorexia: >70% ◦ Nausea: >65% ◦ Vomiting: 50–75% ◦ Constipation/Diarrhea: 4–16% ◦ Fever: 10–20% • Physical Signs (Table 342-3): ◦ Abdominal tenderness: >95% ◦ Right lower quadrant (RLQ) 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% • Classic Maneuvers (Table 342-4): ◦ Rovsing's sign: Palpation of left lower quadrant → pain in right lower quadrant. ◦ Obturator sign: Internal rotation of the hip → pain (suggests pelvic location). ◦ Iliopsoas sign: Extending the right hip → pain along posterolateral back and hip (suggests retrocecal location). ◦ Migration of pain to RLQ: 50–60%. • Atypical Presentations: ◦ Elderly: Minimal pain; nausea, anorexia, and emesis may be predominant. Rarely show signs of distal bowel obstruction. ◦ Children: Dramatic response to stimulation; smaller omentum makes it harder to wall off perforations. ◦ Women of childbearing age: Pelvic examination mandatory to rule out urogynecologic conditions. ◦ Very young or elderly: Signs and symptoms can be subtle.
DIFFERENTIAL DIAGNOSIS¶
• General Rule: Appendicitis must be included in the differential for any patient with abdominal pain unless the organ was previously removed. ◦ Conditions Mimicking Appendicitis (Table 342-1): ◦ Crohn's disease, Meckel's diverticulitis, Cholecystitis or other gallbladder disease, COVID-19 infection (occasionally co-incident), Diverticulitis, Ectopic pregnancy, Endometriosis, Gastroenteritis or colitis, Gastric or duodenal ulceration, Hepatitis, Kidney disease (including nephrolithiasis), Liver abscess, Mittelschmerz, Mesenteric adenitis, Omental torsion, Pancreatitis, Lower lobe pneumonia, Pelvic inflammatory disease, Ruptured ovarian cyst or other cystic disease of the ovaries, Small-bowel obstruction, Urinary tract infection.
INVESTIGATIONS & DIAGNOSIS¶
• Laboratory Testing: ◦ WBC: 70% have mild/moderate elevation (10,000–18,000 cells/μL). ◦ Left shift: Present in >95% of cases. ◦ Urinalysis: To exclude genitourinary conditions; may show non-specific white or red blood cells if the appendix abuts the ureter or bladder. ◦ Pregnancy Test: Mandatory for every woman of childbearing age. ◦ Other: Serum amylase/lipase (to rule out other causes); sickle cell preparation for specific ethnicities; cervical cultures if PID suspected. • Imaging: ◦ Plain films: Rarely helpful; <5% show an opaque fecalith in the RLQ. ◦ Ultrasonography: Sensitivity ~0.86, Specificity 0.81; highly operator dependent; most useful for identifying pelvic pathology in women. Findings include wall thickening, increased diameter, and free fluid. ◦ Computed Tomography (CT): Sensitivity ≥0.94, Specificity 0.95. Superior for assessing severity and complications. → Criteria: Dilatation >6 mm, wall thickening, and fatty tissue stranding or air surrounding the appendix. → Note: Nonvisualization of the appendix is non-specific and does not rule out inflammation. • Diagnostic Algorithm: 1. History and Physical Examination. 2. Laboratory Testing (WBC, Urinalysis, Pregnancy Test). 3. Imaging (Ultrasound or CT) if diagnosis is uncertain or complications suspected. 4. Surgical Consultation for Appendectomy if diagnosis is confirmed or highly suspected. 5. Observation and repeat examination over 6–8 h if diagnosis is uncertain.
MANAGEMENT & TREATMENT¶
- Appendectomy: ◦ Choice: Laparoscopic or open (both are satisfactory; laparoscopic preferred for recovery and obese patients). ◦ Post-operative: Most can be discharged within 24–40 h. ◦ Monitoring: Fever and leukocytosis persisting beyond 5 days suggest an intraabdominal abscess.
- Abscess Management: ◦ Condition: Patients presenting with a mass (phlegmon or abscess). ◦ Treatment: Broad-spectrum antibiotics, parental fluids, bowel rest, and percutaneous drainage (especially if abscess >3 cm). ◦ Follow-up: Interval appendectomy 6–12 weeks later once inflammation has diminished.
- Peritonitis Therapy: ◦ Fluid resuscitation to correct electrolyte abnormalities and stabilize cardiovascular system. ◦ Antibiotics for infection. ◦ Surgical correction of underlying anatomical issues (e.g., perforation, diverticulitis).
PROGNOSIS & COMPLICATIONS¶
• Mortality Rates: ◦ Uncomplicated/Nonperforated: 0.1–0.5%. ◦ Perforated: 3% overall; up to 15% in elderly. ◦ Pregnancy: Fetal mortality is four times greater (from 5% to 20%) in patients with perforation. • Complications: ◦ Abscess formation, Sepsis, Phlegmon, Perforation, Intrahepatic abscesses (if portal vein thrombosis occurs).
SPECIAL CONSIDERATIONS¶
• Pregnancy: Diagnosis is more challenging; pelvic examination mandatory. High index of suspicion required due to fetal risk. ◦ Elderly: Symptoms may be subtle; pain may be minimal or localized only where the appendix is located. Nausea, anorexia, and emesis may be predominant. ◦ Children: Tend to respond dramatically to stimulation; smaller omentum makes it harder to wall off perforations. ◦ Immunocompromised: May present with only mild tenderness; risk of atypical infections (mycobacteria, CMV, fungi). Enterocolitis may be present in patients with fever and neutrophysia from chemotherapy.
KEY PEARLS & CLINICAL TRAPS¶
• Anorexia: If absent, the diagnosis of appendicitis should be questioned. ◦ Nausea Timing: Nausea usually follows pain (distinguishes from gastroenteritis). ◦ Surgical Choice: Laparoscopic approach may facilitate exposure in very obese patients or when diagnosis is uncertain. ◦ Imaging Utility: CT is superior for assessing severity and identifying complications (abscess, phlegmon) when diagnosis is uncertain.
Reference Tables¶
TABLE 342-1 Some Conditions That Mimic Appendicitis Crohn’s disease Cholecystitis or other gallbladder disease COVID-19…¶
Harrison's 22e, p.2594
| 342 | Acute Appendicitis and Peritonitis Danny O. Jacobs |
|---|---|
TABLE 342-1 Some Conditions That Mimic Appendicitis
| Crohn’s disease Cholecystitis or other gallbladder disease COVID-19 infection occasionally co-incident Diverticulitis Ectopic pregnancy Endometriosis Gastroenteritis or colitis Gastric or duodenal ulceration Hepatitis Kidney disease, including nephrolithiasis Liver abscess |
Meckel’s diverticulitis Mittelschmerz Mesenteric adenitis Omental torsion Pancreatitis Lower lobe pneumonia Pelvic inflammatory disease Ruptured ovarian cyst or other cystic disease of the ovaries Small-bowel obstruction Urinary tract infection |
|---|---|
TABLE 342-3 Relative Frequency of Some Presenting Signs SIGNS Abdominal tenderness Right lower quadrant tenderness…¶
Harrison's 22e, p.2595
| SIGNS | FREQUENCY |
|---|---|
| Abdominal tenderness | >95% |
| Rebound tenderness | 30–70% |
| Cervical motion tenderness | 30% |
| Psoas sign | 3–5% |
| Rovsing’s sign | 5% |
TABLE 342-2 Relative Frequency of Common Presenting Symptoms SYMPTOMS Abdominal pain Anorexia Constipation Diarrhea…¶
Harrison's 22e, p.2595
| SYMPTOMS | FREQUENCY |
|---|---|
| Abdominal pain | >95% |
TABLE 342-4 Classic Signs of Appendicitis in Patients with Abdominal Pain MANEUVER Rovsing’s sign Obturator sign…¶
Harrison's 22e, p.2595
| MANEUVER | FINDINGS |
|---|---|
| Rovsing’s sign | Palpating in the left lower quadrant causes pain in the right lower quadrant |
| Constipation | 4–16% |
| Fever | 10–20% |
| Nausea | >65% |
| Iliopsoas sign | Extending the right hip causes pain along posterolateral back and hip, suggesting retrocecal appendicitis |
TABLE 342-5 Conditions Leading to Secondary Bacterial Peritonitis Bowel perforation¶
Harrison's 22e, p.2597
| Bowel perforation Appendicitis Anastomotic leakage Adhesion Diverticulitis Iatrogenic (including endoscopic perforation) Ingested foreign body Inflammation Intussusception Neoplasms Obstruction Peptic ulcer disease Strangulated hernia Vascular (including ischemia or embolus) Trauma (blunt or penetrating) |
Perforation or leakage of other organs Biliary leakage (e.g., after liver biopsy) Cholecystitis Intraperitoneal bleeding Pancreatitis Salpingitis Urinary bladder Loss of peritoneal integrity Intraperitoneal chemotherapy Iatrogenic (e.g., postoperative foreign body) Perinephric abscess Peritoneal dialysis or other indwelling devices Trauma |
|---|---|