doi:10.1016/j.jemermed.2008.01.011 Selected Topics: Emergency Radiology RADIOGRAPHIC LOOK-ALIKES: DISTINGUISHING BETWEEN PNEUMOPERITONEUM AND PSEUDOPNEUMOPERITONEUM Bruce M. Lo, MD Department of Emergency Medicine, Eastern Virginia Medical School, Norfolk, Virginia Reprint Address: Bruce M. Lo, MD, Department of Emergency Medicine, Eastern Virginia Medical School, Raleigh Building, Room 304, 600 Gesham Drive, Norfolk, VA 23507 e Abstract—Background: Air under the diaphragm seen on plain radiograph usually signifies a perforated viscus. This represents a surgical emergency and an immediate consult with the surgeon. However, not all air under the diaphragm seen on plain radiograph represents a surgical emergency. Objectives: This article will present two cases with air under the diaphragm, but with different diagnoses and management. The first case is an example of pneumo- peritoneum from a perforated viscus. The second case is an example of pseudopneumoperitoneum from Chilaiditi syn- drome, which will be discussed. Case Reports: The first case is a 45-year-old woman who presented with bloating, nau- sea, and vomiting after being diagnosed with diverticulitis 4 days before evaluation. The patient was noted to be febrile and tachycardic. A chest radiograph was obtained, which showed air under the diaphragm. A surgeon was consulted who performed a laparotomy on the patient. Patient was diagnosed with a perforated viscus from a sigmoid diver- ticulitis. The second case is a 68-year-old woman who pre- sented with right-sided abdominal pain, cough, nausea, and vomiting. A chest radiograph showed possible free air un- der the diaphragm. A computed tomography scan of the abdomen showed Chilaiditi syndrome, large bowel trans- posed between the liver and the diaphragm, but no free air. The patient was treated symptomatically and discharged home. Conclusion: It is important for physicians to be able to distinguish pneumoperitoneum and pseudopneumoperi- toneum to allow proper diagnosis and treatment. © 2010 Elsevier Inc. e Keywords—pneumoperitoneum; pseudopneumoperito- neum; Chilaiditi syndrome; CT scan; X-ray study INTRODUCTION Air under the diaphragm seen on plain radiograph usually represents pneumoperitoneum from a perforated viscus and is usually an indication for immediate surgical exploration. However, air under the diaphragm on plain radiograph may represent pseudopneumoperitoneum such as Chilaiditi syn- drome. This rare finding seldom requires operative interven- tion. Distinguishing between pneumoperitoneum and pseu- dopneumoperitoneum can be diagnostically challenging. CASE REPORTS Case 1 A 45-year-old woman presented with a sensation of bloating that had been increasing over several days. She was seen 4 days prior in the Emergency Department (ED) for severe abdominal pain and diagnosed with diverticulitis by computed tomography (CT). She was discharged with ciprofloxacin and metronidazole. She reported resolution of pain, but had been having persis- tent nausea and fevers. Her past medical history was significant for rheumatoid arthritis and she was taking methotrexate and leflunomide. She was febrile with an oral temperature of 39.1°C (102.4°F), heart rate of 145 beats/min, respiratory rate of 16 breaths/min, blood pressure of 144/85 mm Hg, and pulse oximetry of 99% on room air. On examination she RECEIVED: 26 September 2007; FINAL SUBMISSION RECEIVED: 27 December 2007; ACCEPTED: 6 January 2008 The Journal of Emergency Medicine, Vol. 38, No. 1, pp. 36 –39, 2010 Copyright © 2010 Elsevier Inc. Printed in the USA. All rights reserved 0736-4679/08 $–see front matter 36