See also Acute Abdominal Pain

I. Epidemiology and pathophysiology
  1. Peak incidence at 10-30yo
  2. Thought to result from obstruction of the lumen of the appendix, e.g. due to stool, lymphoid hyperplasia, vegetable matter, parasites, or neoplasm)
  3. End result is mucosal ischemia and ulceration with bacterial obergrowth, which can progress to gangrene and perforation
  4. Perforation
    1. Occurs in 20-30% of cases
    2. Typically occurs 48-72h from onset of symptoms
    3. Can result in peritonitis and sepsis
    4. Incidence is highest in patients < 3yo and > 50yo as well as immunosuppressed or pregnant patients
  5. Infective agents are usually gram-negative, most commonly E. coli, but can also have involvement of Strep viridans, Group D Strep, Pseudomonas aeruginosa, and Enterococcus

II. Clinical features and Diagnosis
  1. Diagnosis can be difficult due to nonspecific and variable presentation
  2. Typical clinical features
    1. Abdominal pain
      1. Usually progressive over 12-24h
      2. Initially colicky and poorly-localized or periumbilical, shifting to RLQ, worse with movement and increases in intra-abdominal pressure, and not relieved by defecation.
      3. Absence of migration of pain occurs in about 25% of cases
      4. Pain may radiate to right testicle in men
    2. Anorexia occurs in 90% of cases
    3. Nausea and vomiting occur in 60-80% of cases (abdominal pain should precede vomiting; if abdominal pain starts after vomiting, should call diagnosis into question.
    4. Fever occurs in 70% of cases (often absent in elderly and immunosuppressed patients)
    5. Abdominal tenderness
      1. Present in > 95% of patients
      2. Cutaneous hyperesthesia may be present in "Sherren's triangle" (umbilicus-pubic tubercle-anterior super iliac spine)
      3. Rebound tenderness in RLQ seen in about 50% of patients
    6. Psoas sign (holding hip in flexion due to spasm of psoas muscle, with worsening of pain with passive extension of hte hip)-Can see in retrocecal appendicitis
    7. Leukocytosis has sensitivity 76% and specificity of 52%
    8. Elevation of CRP is usually present
    9. Urinalysis may show hematuria and/or pyuria
  3. Clinical presentation may vary based on location of appendix: retrocecal, pelvic,and other
    1. Retrocecal (65% of cases)-Rarely have diarrhea
    2. Pelvic (30% of cases)-May have diarrhea, tenesmus, and/or lower urinary tract symptoms; Also may have tendereness of lateral rectal and/or vaginal walls
    3. Other (< 5% of cases)-May have diarrhea
  4. Course if untreated
    1. Usually perforation, peritonitis, and sepsis
    2. Sponaneous resolution occurs in about 10% of patients who do not undergo surgery
    3. Appendiceal abscess may form
    4. Perforation may lead to fistula formation with other bowel structure or pevic organs (or abdominal wall)
  5. CT for acute appendicitis
    1. Had  sensitivity of 99% and specificty of 95% for acute appendicitis in a case series of 63 children presenting to an ED with abdominal pain (Am. J. Roentgenol. 184:1802, 2005--JW)
    2. In a study in 2,800 adults with suspected acute appendicitis, multi-detector CT had sensitivity of 98.5% and specificity of 98.0% (Ann. Int. Med. 154:789, 2011-JW)
  6. Ultrasound for acute appendicitis
    1.  Sensitivity of 83% and specificity of 95% for acute appendicitis in a case series of 667 adults and children with suspected appendicitis (Am. J. Roentgenol. 184:1809, 2005--JW)
  7. Diagnosis of acute appendicitis in children with abdominal pain
    1. In a systematic review of studies comparing clinical findings with histologically confirmed appendicitis (West. J. Med. 176:104, 2001-AFP), the following were significantly associated with that diagnosis:
    1.  Not associated with sig. increased likelihood of appendicitis:
      • Rectal tenderness
      • Length of time that pain has been present

(Sources include Core Content Review of Family Medicine, 2012)