Consider the Probe v2
A 29-year old man presents as a TTA after a motor vehicle accident at 60 mph. Your exam
reveals a seatbelt sign with abdominal tenderness. His vital signs are currently all within normal
limits. You appropriately reach for an ultrasound to complete an eFAST exam and in the right
upper quadrant (Figure 1) you see the following:
Figure 1.
What do these ultrasound findings suggest and what are your next steps?
POCUS Interpretation: Trace anechoic stripe tracing the liver border seen in hepatorenal
space and medial to right kidney. Indeterminate FAST.
This finding should prompt you to PAUSE and investigate further as this COULD indicate a
positive eFAST exam. However, there are several features of the findings in these specific
images that indicate that this is NOT an intraabdominal hemorrhage but rather a recently
described artifact called The Lipliner Sign [1]. So, from these images, how do we tell the
difference?
The Focused Abdominal Sonogram for Trauma (FAST) Exam
The FAST exam was first described in 1996. At that time, ultrasound machines had spatial
resolution in tissue that ranged roughly from 1 to 3 millimeters. The initial algorithm proposed
use of the FAST exam for hypotensive patients with blunt truncal trauma to determine
disposition to the OR or to the CT scanner [2]. However, a positive FAST exam only requires
100-200cc of blood to detect with ultrasound, while vital sign changes require a loss of at least
750cc of blood [3-4]. This fact strongly reinforces the concept that we should be
performing early, and if indicated, repeat, or serial FAST exams on all of our trauma
patients to detect early blood loss before it becomes hemodynamically compromising.
On ultrasound a positive FAST is seen as a collection of anechoic or mixed anechoic and
hypoechoic borderless fluid in the right-upper, left-upper, pelvic, or thoracic windows of the
eFAST exam. We often particularly focus on the right upper quadrant view (RUQ) as this is often
where fluid first accumulates. The RUQ view is also the most sensitive in adults; one study
demonstrated that the majority (67%) of patients had a positive FAST in the RUQ and of these
patients, 94% had a positive FAST at the caudal tip of the liver, making this the most sensitive
area of the entire FAST exam [5].
The Lipliner Sign
This artifact was described in 2024 and, at present, modern ultrasound machines can have
spatial resolutions in tissue down to 0.03 to 1 millimeters! These advances in image resolution
and postprocessing enhancement are to blame for the emergence of this artifact we now call
The Lipliner Sign. It is described as appearing as a thin anechoic line along the edges of solid
organs, most notably the liver and spleen [1].
Tips & Tricks to Differentiate +FAST from Lipliner
1. Where is the fluid?
The Lipliner Sign appears as a thin and uniformly linear anechoic stripe that follows the
contour of the solid organ in question. This structure is consistently noted to be anterior
to the distinct border or hyperechoic capsule of the liver or spleen (Figure 2a). In a
positive FAST exam, the fluid appears as a variably sized, wedge shaped (as it tapers
between organs into dependent spaces) or borderless anechoic pocket. The fluid is
typically inferior to the distinct border or hyperechoic capsule of the liver or spleen
(Figure 2b).
Figure 2.
2. Don’t Forget The Liver Tip!
Remember, the liver tip is the most sensitive area for intraabdominal fluid on the FAST
exam in adults (Figure 3)–in pediatrics it’s the pelvis. This should be a mandatory view
for all emergency physicians and should be incorporated into your routine practice. If
you miss the liver tip, you may miss early (100-200cc) bleeds!
Figure 3.
3. Use Gravity.
After characterizing the location of the RUQ fluid and checking the liver tip, you still
aren’t sure if this FAST is equivocal or positive, so what do you do? In a supine patient,
blood is dependent and will pool posteriorly in the abdomen. One study described the
FASTeR exam–FAST examination after Right-Sided Roll where patients were first rolled
into right lateral decubitus for 30 seconds after which the FAST exam was repeated. This
increased FAST exam sensitivity, converting previously false-negatives to true positives
[6]. With an indeterminate Lipliner versus +FAST exam, an increase in fluid volume in
the RUQ would indicate a +FAST. Alternatively, the patient can be placed in
Trendelenburg position and the FAST can be performed (either initially or as an
augmentation tool) looking again for an increase in fluid volume to detect a +FAST.
4. Serialize your Exams.
In a trauma setting, this is probably the end of the bedside assessment as the patient will
likely go to CT or to the OR. But in non-trauma patients, or trauma patients back in the
ED with CT negative initial imaging and changing abdominal exams, repeat your FAST
exams every 15 minutes. You may detect changes in RUQ fluid volume over time that
finally leads to a diagnosis of intraabdominal hemorrhage.
References
1. Parker MA, Hicks BG, Kaili M, et al. The Lipliner Sign: Potential Cause of a False
Positive Focused Assessment with Sonography in Trauma (FAST) Examination. J
Emerg Med. 2024;67(6):e553-e559. doi:10.1016/j.jemermed.2024.06.013
2. Rozycki GS, Ballard RB, Feliciano DV, Schmidt JA, Pennington SD. Surgeon-performed
ultrasound for the assessment of truncal injuries: lessons learned from 1540 patients.
Ann Surg. 1998;228(4):557-567. doi:10.1097/00000658-199810000-00012
3. Bloom BA, Gibbons RC. Focused Assessment With Sonography for Trauma. StatPearls
[Internet]. 2026. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470479/
4. Hooper N, Armstrong TJ. Hemorrhagic Shock. StatPearls [Internet]. 2026. Available
5. Lobo V, Hunter-Behrend M, Cullnan E, Higbee R, Phillips C, Williams S, Perera P,
Gharahbaghian L. Caudal Edge of the Liver in the Right Upper Quadrant (RUQ) View Is
the Most Sensitive Area for Free Fluid on the FAST Exam. West J Emerg Med. 2017
Feb;18(2):270-280. doi: 10.5811/westjem.2016.11.30435. Epub 2017 Jan 19. PMID:
28210364; PMCID: PMC5305137.
6. Pigneri DA, Behm RJ, Granet PJ. Rolling a trauma patient onto the right side increases
sensitivity of FAST examination. J Clin Ultrasound. 2020;48(3):152-155.
doi:10.1002/jcu.22797
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