Diseases that simulate acute appendicitis on ultrasound.

Ultrasound is useful in the assessment of patients with possible appendicitis. A diagnosis of appendicitis can be made in patients with persistent right lower quadrant pain when a non-compressible appendix greater than 6 mm in diameter is shown. When a normal appendix is affected by an adjacent lesion, reactive inflammation can cause secondary enlargement of the appendix. This article reviews ultrasound findings in conditions which can clinically mimic acute appendicitis. Examples of Crohn's disease, tuboovarian abscess, typhilitis, sigmoid diverticulitis, perforated sigmoid neoplasm, perforated peptic ulcer, perforated acute cholecystitis, caecal carcinoma and appendiceal tumours are included.