Which imaging finding is most reliable for detecting pneumoperitoneum in an unstable patient?

Which imaging finding is most reliable for detecting pneumoperitoneum in an unstable patient?

• A. Free intraperitoneal air on upright radiographs or CT
• B. Abdominal ultrasound
• C. MRI
• D. Lateral decubitus radiographs

Answer: (A)

Detecting free air in the peritoneal cavity is the most reliable sign of pneumoperitoneum, especially when a patient is unstable and time is critical. The direct visualization of free intraperitoneal air beneath the diaphragm on upright radiographs (chest or abdominal) provides a rapid, highly specific indication of hollow viscus perforation. If the patient can be moved to CT and stability permits, CT is even more sensitive for detecting free air, but in an unstable patient the quickest practical and most reliable option is to look for air on an upright film. Ultrasound is excellent for identifying free fluid and solid organ injury at the bedside, but it is far less reliable for detecting free air; MRI isn’t suitable in the emergent setting; and a lateral decubitus film can help if upright positioning isn’t possible, though it’s less sensitive than upright imaging.

Detecting free air in the peritoneal cavity is the most reliable sign of pneumoperitoneum, especially when a patient is unstable and time is critical. The direct visualization of free intraperitoneal air beneath the diaphragm on upright radiographs (chest or abdominal) provides a rapid, highly specific indication of hollow viscus perforation. If the patient can be moved to CT and stability permits, CT is even more sensitive for detecting free air, but in an unstable patient the quickest practical and most reliable option is to look for air on an upright film. Ultrasound is excellent for identifying free fluid and solid organ injury at the bedside, but it is far less reliable for detecting free air; MRI isn’t suitable in the emergent setting; and a lateral decubitus film can help if upright positioning isn’t possible, though it’s less sensitive than upright imaging.