Gangrenous Appendicitis

This 71 year-old male had an abdominal CT for investigation of septicaemia and right upper quadrant tenderness. The oblique coronal image shows fat stranding around a gas-filled and distended appendix (large arrow) and extraluminal gas adjacent to it (arrowheads). There was a faecolith at the appendix base (not shown). The findings are consistent with perforation of a gangrenous appendix.
Gas within the appendix is usually a sign of normality. This case clearly shows that this is not always true. Extraluminal gas has been evaluated along with four other findings for the assessment of perforation: extraluminal appendicolith, abscess, phlegmon, and a defect in the enhancing appendiceal wall. Each of these findings have a high specificity but a low sensitivity. By looking for all findings rather than just one, the sensitivity for perforation can be increased to 95%. The implication of this is that if one finding is present, perforation is likely, and if all are absent, perforation is unlikely.
Reference:
Horrow MM, White DS, Horrow JC. Differentiation of Perforated from Nonperforated Appendicitis at CT. Radiology 2003;227:46-51
Credit: Dr Laughlin Dawes
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