The "inverted V": a new sign of pneumoperitoneum.

Abstract Three cases are presented in which a new sign of pneumoperitoneum is recognized. Free air outlining the lateral umbilical ligaments makes these structures visible in the lower abdomen, forming an “inverted V” as they course inferiorly and laterally from the umbilicus. The ligaments contain the umbilical arterial remnants and may be unilaterally or fractionally visualized.