Appendicitis: continuing diagnostic challenge.

Recognition of appendicitis depends on an understanding of the underlying pathophysiology and anatomy that shape the clinical presentation. Knowledge of the clinical symptoms and signs that distinguish between appendicitis and competing diagnoses enables the clinician to differentiate appendicitis from other pathologies. Variations in anatomy, pathophysiology, symptoms, and signs are described for adult men, ovulating women, pregnant women, children, the elderly, and immunocompromised patients.