Esophageal diverticula are classified into two types depending on there mechanism of formation.

Patient A: Pulsion diverticula

 Pulsion diverticula are formed due to increased intraluminal pressure mostly due to an esophageal motility disorder. On barium study they usually rounded counter and a wide neck and are frequently multiple. Because they contain no muscle layer in there wall, they tend to remain filled after the esophagus has emptied of barium.

Patient B: Traction diverticula

 Traction diverticula are formed due to scarring and retraction by granulomatous disease in adjacent subcarinal and perihilar lymph nodes. On barium study they have tented or triangular configuration and are located in mid esophagus. They contain all layers of esophageal wall, so they tend to empty when esophagus collapses.