Figure 15a. Torsion of a Meckel diverticulum causing small intestinal obstruction in a 30-year-old man who presented with abdominal distension and vomiting. Supine (a) and upright (b) abdominal radiographs show features of a mechanical small intestinal obstruction and an oval air collection that contains multiple peripherally calcified stones (arrow) in the right lower quadrant. At surgery, these findings proved to represent torsion of a Meckel diverticulum and multiple enteroliths. (Courtesy of Charles Rohrmann, Jr, MD, University of Washington, Seattle.)