Visualization of the extrahepatic segment of the ligamentum teres: a sign of free air on plain radiographs.

PURPOSE: To assess visualization of the extrahepatic segment of the ligamentum teres on plain radiographs, the ligamentum teres sign, which is an indicator of pneumoperitoneum.

MATERIALS AND METHODS: The ligamentum teres was recognized in 12 patients with pneumoperitoneum. Findings from supine radiographs were correlated with those from oblique radiographs and computed tomograms.

RESULTS: The extrahepatic segment of the ligamentum teres, which extended between the umbilicus and the ligamentum teres notch at the inferior border of the liver, was visualized on supine radiographs. The ligamentum teres appeared in the right upper quadrant as an obliquely oriented, straight, or slightly arcuate interface with a sharply demarcated inferolateral margin or as a similarly positioned, well-defined band of soft tissue of varying length. The falciform ligament was also seen in six of the 12 patients as a long, thin line that ran vertically to the right of the midline and joined the ligamentum teres caudally near or at the umbilicus. Even though there were other signs of pneumoperitoneum in all cases, the ligamentum teres sign was the most prominent in three cases.

CONCLUSION: Visualization of the extrahepatic segment of the ligamentum teres on supine radiographs requires the anterior accumulation of extraluminal, intraperifoneal gas and is another sign of moderate to massive amounts of free air.