Pseudo-pneumoretroperitoneum secondary to lumbar emphysema: CT demonstration in two cases

Several conditions may simulate the radiolucent appearances of pneumoretroperitoneum at plain film. These include gas shadows in locations other than the retroperitoneal space or fluid within the retroperitoneal compartments. Two cases of emphysema within the soft tissues of the back mimicking pneumoretroperitonium on plain radiographs are described. One case was secondary to epidural anesthesia and another to trauma. In both, computed tomography (CT) led to the correct diagnosis. The possible pitfalls in the differential diagnosis of retroperitoneal gas are described with emphasis of the diagnostic role of CT.