Prevalence of the Lipliner Sign in Focused Assessment With Sonography for Trauma Examinations and Its Potential Harms

The Focused Assessment with Sonography for Trauma (FAST) examination is a cornerstone of trauma resuscitation, allowing for early recognition of hemoperitoneum to guide management. Because FAST findings can directly affect immediate care, even small rates of misinterpretation carry the potential for significant downstream harm. In late 2024, a novel FAST artifact, the “lipliner sign”, was described as a mimic of hemoperitoneum after four experienced clinicians misclassified this finding as free intraperitoneal fluid. However, the prevalence of this artifact in routine clinical practice and its real-world impact on patient management remain unknown. The objective of our study was to determine the prevalence of the lipliner sign in FAST examinations and explore its potential impact on clinical decision-making.

We performed a single-center, retrospective chart review of FAST exams conducted between August 2024 and September 2025. All available studies were screened for the presence of the lipliner sign, and associated clinical actions were reviewed such as BMI, shock index, and false positive rates. All FAST examinations demonstrating the lipliner sign were independently reviewed and verified by ultrasound-trained faculty.

Of 641 FAST examinations reviewed, 600 had confirmatory testing. 142 of these demonstrated the lipliner sign, yielding a prevalence of 29% (95% CI 25.4-32.4). Most cases occurred in patients with blunt trauma (78%). Seven cases (7/142, 5%) were false-positive interpretations that led to escalation of care, including trauma activation upgrade, early trauma consultation, and admission for serial abdominal examinations despite negative computed tomography (CT) findings.

The lipliner sign is a common FAST artifact with the potential to meaningfully impact clinical decision-making. Improved recognition may reduce false-positive FAST interpretations, unnecessary CT imaging, and inappropriate downstream interventions. Future studies comparing ultrasound platforms and image-processing settings may help identify technical strategies to reduce this artifact and improve FAST accuracy.