APPROXIMATELY 90% of cases of spontaneous pneumoperitoneum are the result of acute abdominal conditions that will subsequently require emergency surgery.1 The life-threatening nature of these conditions requires prompt and accurate diagnosis.
Pneumoperitoneum may be obvious or may be demonstrated as the result of a carefully planned examination directed toward that diagnosis. It may be encountered as a fortuitous observation in the course of a study performed for other purposes.
The most sensitive method of verifying pneumoperitoneum relies on directing the horizontal x-ray beam tangentially to the collection of free air. Therefore, a purposeful examination with that diagnosis in mind should be designed to achieve the optimal detection consistent with the condition of the patient. On the other hand, it is essential that the roentgenographic manifestations of free intra-abdominal air in all of the various techniques of abdominal examination be known so that a chance demonstration will not be overlooked.
Paster SB, Brogdon BG. Roentgenographic Diagnosis of Pneumoperitoneum. JAMA. 1976;235(12):1264-1267. doi:10.1001/jama.1976.03260380058035