Sonographic detection of normal and abnormal appendix

The aim of the study was to assess the value of sonography in detecting the normal appendix and in identifying abnormality.

The appendiceal wall thickness (normal: <3 mm) and ultraluminal contents (abnormal: large appendicolith, non-expressible fluid) were used as the primary criteria to determine the appendiceal status in 716 appendices. In patients who underwent appendicectomy (n = 166), surgical and histopathological findings were correlated with the ultrasound (US) findings; in patients who did not have surgery the reference standard was the clinical consensus based on follow-up.

Thirty-four patients out of 179 with abnormal sonographic findings did not undergo appendicectomy and recovered spontaneously; in 22 of these, the US changes were confined to the appendiceal tip. A normal appendix was identified in 537 patients (45.9% of all patients without appendicitis), with histologic verification subsequently obtained in 21. In 76 normal appendices (14.2% out of all normal appendices), luminal dilatation due to non-expressible inspissated faeces resulted in appendiceal outer diameter >6 mm (range, 6.2-12 mm); a histopathologic proof of non-inflamed appendix was obtained in seven of these.

A normal appendix can be visualized in a high percentage of cases and it may present with an outer diameter >6 mm (the widely-accepted upper limit of normal) due to the inspissated faecal material within the lumen. A significant percentage of early appendicitis can resolve spontaneously, especially when confined to the appendiceal tip.