Appendicular involvement in perforated sigmoid disease: US and CT findings.

We describe four patients in whom ultrasound (US) and/or computed tomography (CT) demonstrated a thickened appendix, secondarily enlarged due to perforated sigmoid diverticulitis (n = 2) or carcinoma (n = 2). The underlying pathology was correctly recognized in all cases. Secondary thickening of the appendix due to perforated sigmoid disease provides a potential pitfall mainly on US and may lead to an incorrect diagnosis and thus to unnecessary surgery or a wrong surgical intervention. Although US alone is enough to diagnose periappendicitis and sigmoid disease, combined use of US and CT may improve assessment of its origin and extension.