Imaging of pneumoperitoneum.

Source: PubMed, NCBI / U.S. National Library of Medicine

The exclusion of free intraperitoneal gas (pneumoperitoneum) is one of the most common indications for imaging in patients presenting with clinical signs of acute abdominal pain. Among radiological methods, upright abdominal and chest radiographs are commonly used for the dia-gnosis of pneumoperitoneum; however, they have the lowest reported sensitivity for detecting free intraperitoneal air. Native or contrast-enhanced computed tomography is considered the gold standard in this dia-gnostic setting, although it exposes patients to the highest levels of ionizing radiation. Ultrasonography is also used in the dia-gnosis of pneumoperitoneum, but it is a highly operator-dependent modality, relying significantly on the examiner's experience. This article presents typical imaging features of pneumoperitoneum across various modalities, as well as less common and potentially misleading findings.