- The current article revolves upon the challenge of diagnosing free peritoneal air in an abdominal X-ray. We present an 80 year old lady who was admitted due to abdominal pain and vomiting. On an acute abdomen XR series, a small amount of free air was suspected, but this was inconclusive. This article focuses upon the complexity of diagnosing abdominal free air Acute abdomen radiography is an essential tool in the evaluation of an acute abdomen, and research has shown that an acute abdominal X-ray series appropriately conducted and interpreted by qualified experts can show as little as 1 cc of free air in the peritoneum. Other studies, on the other hand, have shown that 30-50% of patients with bowel perforation, especially in the elderly population, will not show signs of free air on X-rays. We believe that the proper evaluation and diagnosis of free air involves a methodical approach. First one should begin with an acute abdominal X-ray series. It is advised to have the patient stand or lie in the left decubitus position for 10-15 minutes before the X-rays are conducted. Use of high resolution monitors to enhance the visual acuity and consulting an expert radiologist can help when in doubt. If one is still not sure, it is recommended to perform a CT scan, which is the gold standard for detecting free peritoneal air.