Sonographically detected free appendicolith as a sign of retrocecal perforated appendicitis in a 2-year-old child.

Prompt and accurate diagnosis of perforated appendicitis is crucial for proper and timely treatment. The appendix, however, cannot always be identified with sonography (US). We report the case of a 2-year-old child with atypical clinical presentation, and US detection of a free appendicolith as a sign of perforated appendicitis, without visualization of the appendix itself. Laparoscopy revealed a retrocecal, gangrenous, perforated appendix with autoamputation, fibrinopurulent peritonitis, and a free appendicolith within the abdominal fluid. US detection of a free appendicolith in a child is a very rare, but unequivocal sign of perforated appendicitis, which should be sought. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:395-398, 2016.