Final answer:
The lateral decubitus position is preferred for radiographs to demonstrate air-fluid levels in the abdomen, as it allows air to rise, aiding in the visualization of these levels.
Step-by-step explanation:
The preferred radiographic decubitus position for demonstrating air-fluid levels in the abdomen is the lateral decubitus position, with the patient lying on their side. This position is often used when an upright position is not possible due to the patient's condition. When the patient is positioned on their side, air rises to the highest point, which allows for easy visualization of air-fluid levels on radiographs, such as an abdominal X-ray or a computed tomography (CT) scan. These imaging techniques are crucial in diagnosing conditions that may involve fluid accumulation or free air in the abdominal cavity, providing valuable information for medical diagnosis and treatment planning.