Physiologic Reduction of Hepatic Venous Blood Flow by the Valsalva Maneuver Decreases Liver Stiffness.
OBJECTIVE
Liver stiffness increases after intake of food or water, suggesting that hepatic venous blood flow affects the results of elastographic measurements. This study investigated the correlation between in vivo liver stiffness and hepatic blood flow using the Valsalva maneuver for reducing intrahepatic venous blood flow.


METHODS
Intrahepatic changes in venous blood flow were assessed by sonography based on the pulsed wave Doppler velocity, vessel diameter assessment, and blood flow volume measurements in the portal vein and right hepatic vein. Time-harmonic elastography at 7 harmonic driving frequencies (30-60 Hz) was used to measure liver stiffness in the right liver lobe of 15 healthy volunteers.


RESULTS
The right hepatic vein diameter, flow volume, and peak pulsed wave velocity decreased during the Valsalva maneuver from mean ± SD values of 8.64 ± 1.85 to 6.55 ± 1.84 mm (P = .002), 0.53 ± 0.23 to 0.37 ± 0.26 L/min (P = .037), and 22.14 ± 4.87 to 17.38 ± 5.41 cm/s (P = .01), respectively. This maneuver decreased liver stiffness in all volunteers by a mean of approximately 13% from 1.71 ± 0.22 to 1.48 ± 0.22 m/s (P = .00006).


CONCLUSIONS
Our results demonstrate that liver stiffness is sensitive to altered venous blood flow, which is of clinical importance when using elastography for evaluation of portal hypertension. Furthermore, our results indicate that accurate measurement of liver stiffness requires standardized breathing conditions to rule out effects of changes in hepatic blood flow on elastographic findings.
Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Selcan
S
Ipek-Ugay
Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Heiko
H
Tzschätzsch
Department of Institute of Medical Informatics, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Jürgen
J
Braun
Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Thomas
T
Fischer
Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Ingolf
I
Sack
D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006503:Hepatic Veins / Q000000981:diagnostic imaging* / Q000502:physiology*; D006801:Humans; D008099:Liver / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000502:physiology*; D008102:Liver Circulation / Q000502:physiology; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D014636:Valsalva Maneuver / Q000502:physiology*
Valsalva maneuver; breathing; elastography; flow; hepatic vein diameter; liver stiffness; perfusion; time-harmonic waves