Appendicitis and infections of the appendix.

The pathologic spectrum of the acutely inflamed appendix encompasses a wide range of infectious and noninfectious entities. The appendix suffers alone in some of these disorders, and in others may be involved through extension from other areas of the gastrointestinal tract. Although the appendix is the most commonly resected and examined intraabdominal organ, the pathogenesis and etiology of acute nonspecific appendicitis (the most common diagnosis made in this organ) remains enigmatic. This review encompasses the pathology, pathogenesis, and bacteriology of acute appendicitis, as well as controversial issues such as the diagnosis of chronic appendicitis and the significance of a morphologically unremarkable appendectomy specimen in the clinical context of appendicitis. In addition, the pathologic features, pertinent diagnostic techniques, and clinical significance of several specific bacterial, viral, fungal, and parasitic infections affecting the appendix are presented, including adenovirus, cytomegalovirus, Yersinia species, actinomycosis, Mycobacteria species, histoplasmosis, pinworms, schistosomiasis, and Strongyloides stercoralis.