Abdominal supine position is not suitable for positive photography.

Observe the gas-liquid plane of abdominal intestinal obstruction.

When observing the gas-liquid plane of abdominal intestinal obstruction, the standing anteroposterior photography was used. Before and after standing, the patient stands or sits, and the photos are taken from the back and front. This posture is helpful to the natural distribution of gas and liquid in abdominal cavity and shows the gas-liquid plane caused by intestinal obstruction. The gas-liquid plane can't be displayed effectively in supine position. When people are in supine position, gravity will make it easier for gas and liquid to mix and disperse, and it is difficult to accurately display the abnormal situation in the intestine.