Final answer:
In a PA recumbent position during a double-contrast upper GI examination, air will typically be present in the duodenal bulb and gastric fundus due to their anatomical positions.
Step-by-step explanation:
During a double-contrast upper GI examination, certain structures will typically contain air when the patient is in the PA recumbent position. This procedure often involves using a radiopaque substance and air to view the upper gastrointestinal (GI) tract more clearly on X-rays. Knowing the anatomy of the stomach and duodenum helps to understand where air would likely be present. In this position, the air will rise to the highest point.
The gastric fundus is located superior to the body of the stomach, often making it the highest point when the patient is in a recumbent position. We also consider the duodenal bulb, positioned just past the pylorus of the stomach, which may also trap air due to its shape and position. The pyloric vestibule lies between the body of the stomach and the pyloric canal, but because of its position, it is less likely to contain air in this specific position.