The abdominal x-ray shows

a radio opaque density in the right lower quadrant of the abdomen. This is an appendicolith.

Subsequent CT scan of the abdomen revealed an appendicitis.

An appendicolith is seen in about 14% of patients with acute appendicitis. In the right clinical context, there is a positive correlation between appendicolith and acute appendicitis.

Reference: Fundamentals of Diagnostic Radiology by Brant and Helms.