Retroperitoneal abscess associated with closed pelvic ring fracture diagnosed by fine free air on initial trauma pan computed tomography scan.

The patient was a 49-year-old male. He had a closed fracture of the pelvic ring that was treated successfully by avoiding anterior pelvic ring stabilization because of the presence of microscopic free air in the retroperitoneal space behind the pubic bone on initial whole-body trauma computed tomography scan. For his pelvic ring injury, transiliac rod and screw fixation was performed without the need for a pubic symphysis plate by developing the retroperitoneal space. His retroperitoneal abscess was treated by minimally invasive treatment of retroperitoneal abscess with computed tomography-guided percutaneous drainage. At 2 years postoperatively, there was no fever or elevated inflammatory response suspicious of retroperitoneal abscess recurrence. In this case, the presence of microscopic free air influenced the choice of treatment. Even in closed pelvic ring fractures, the presence of free air should be carefully considered when reading images.