The overall accuracy for diagnosing acute appendicitis is approximately 80%. Diagnostic accuracy varies by sex, with a range of 78-92% in male patients and 58-85% in female patients.
The differential diagnosis of appendicitis is often a clinical challenge because appendicitis can mimic several abdominal conditions:
- Pelvic Inflammatory disease (PID) or tubo- ovarian abscess
- Ovarian cyst or torsion
- Crohn's Disease
- Colonic Carcinoma
- Mesenteric adenitis
- Omental Torsion
- Renal Colic
- Urinary Tract Infection
Other problems that should be considered in a patient with suspected appendicitis include appendiceal stump appendicitis, typhlitis & epiploic appendagitis (inflammation of epiploic appendices)
Appendicitis is misdiagnosed in 33% of nonpregnant women of childbearing age. The most frequent misdiagnoses are PID, followed by gastroenteritis and urinary tract infection. Previous PID, vaginal discharge, or urinary symptoms indicates PID. On physical examination, tenderness outside the RLQ, cervical motion tenderness, vaginal discharge, and positive urinalysis support the diagnosis of PID.
Appendicitis in patients older than 60 years accounts for 10% of all appendectomies. The incidence of misdiagnosis is increased in elderly patients.
Appendicitis is misdiagnosed in 25-30% of children, and the rate of initial misdiagnosis is inversely related to the age of the patient. The most common misdiagnosis is gastroenteritis, followed by upper respiratory infection and lower respiratory infection.