Figure 2.

Right Paraduodenal Fossa, aka Waldeyer’s Fossa. The arrow represents the direction of rotation of the small bowel into the fossa. The arrow points into the fossa. The anterior/left edge of the fossa is formed by the tenting of the left mesenteric leaflet around the superior mesenteric vessels. The small bowel rotates around the superior mesenteric vessels to become entrapped behind the transverse mesocolon. This is effectively a partial reversal of mid-gut rotation, or, in some cases, a failure of complete rotation.