In which position will barium fill the fundus of the stomach after a double-contrast upper gastrointestinal series?

When conducting a double-contrast upper gastrointestinal (GI) series utilizing barium, the patient is typically positioned supine for an anteroposterior (AP) view. In this position, barium is able to coat the fundus of the stomach effectively, allowing for clear visualization of the gastric mucosa against the backdrop of the air that has been introduced.

The supine AP position facilitates the collection and distribution of barium throughout the stomach, including the fundus, as it relies on gravity to help spread the contrast agent. Additionally, this position maximizes the area of the stomach that can be imaged, providing better detail and clarity for diagnosis.

Other positions may not adequately distribute barium in the fundus or may result in less desirable imaging for certain diagnostic criteria. For example, in a prone position, the barium might not fill the fundus as effectively due to the influence of gravity working counter to the natural shape of the stomach. Conversely, seated or lateral positions could also create uneven distribution of barium and air, making it more challenging to achieve the best imaging results. Hence, performing the exam in the supine AP position allows for the optimal visualization of the stomach, specifically in the fundus area.