Endogenous motion of liver correlates to the severity of portal hypertension

Abstract

Background: Degree of portal hypertension (PH) is the most important prognostic factor for the decompensation of liver cirrhosis and death, therefore adequate care for patients with liver cirrhosis requires timely detection and evaluation of the presence of clinically significant PH (CSPH) and severe PH (SPH). As the most accurate method for the assessment of PH is an invasive direct measurement of hepatic venous pressure gradient (HVPG), the search for non-invasive methods to diagnose these conditions is actively ongoing.

Aim: To evaluate the feasibility of parameters of endogenously induced displacements and strain of liver to assess degree of PH.

Methods: Of 36 patients with liver cirrhosis and measured HVPG were included in the case-control study. Endogenous motion of the liver was characterized by derived parameters of region average tissue displacement signal (d _antero, d_{r etro}, d _RMS) and results of endogenous tissue strain imaging using specific radiofrequency signal processing algorithm. Average endogenous strain µ and standard deviation σ of strain were assessed in the regions of interest (ROI) (1 cm × 1 cm and 2 cm × 2 cm in size) and different frequency subbands of endogenous motion (0-10 Hz and 10-20 Hz).

Results: Four parameters showed statistically significant (P < 0.05) correlation with HVPG measurement. The strongest correlation was obtained for the standard deviation of strain (estimated at 0-10 Hz and 2 cm × 2 cm ROI size). Three parameters showed statistically significant differences between patient groups with CSPH, but only d _retro showed significant results in SPH analysis. According to ROC analysis area under the curve (AUC) of the σ _{ROI[0…10Hz, 2 cm × 2 cm]} parameter reached 0.71 (P = 0.036) for the diagnosis of CSPH; with a cut-off value of 1.28 μm/cm providing 73% sensitivity and 70% specificity. AUC for the diagnosis of CSPH for µ _{ROI[0…10Hz, 1 cm × 1 cm]} was 0.78 (P = 0.0024); with a cut-off value of 3.92 μm/cm providing 73% sensitivity and 80% specificity. D _retro parameter had an AUC of 0.86 (P = 0.0001) for the diagnosis of CSPH and 0.84 (P = 0.0001) for the diagnosis of SPH. A cut-off value of -132.34 μm yielded 100% sensitivity for both conditions, whereas specificity was 80% and 72% for CSPH and SPH respectively.

Conclusion: The parameters of endogenously induced displacements and strain of the liver correlated with HVPG and might be used for non-invasive diagnosis of PH.

Keywords: Endogenous motion; Hepatic venous pressure gradient; Portal hypertension; Radiofrequency parameters; Strain elastography.

Formula 1

Figure 1

Example illustrating assessment of the endogenous liver displacements and strain. A: region averaged tissue displacement signal obtained in the subsector at time interval (2…3.8) s (three parameters of region averaged displacement signal d_RMS, d_antero and d_retro were evaluated in this study); B: the obtained strain map [amplitude coded in (μm/cm)] together with regions of interest (red rectangle, size 1 cm × 1 cm) used for the local assessment of endogenous strain. ROI: Regions of interest.

Formula 2

Figure 2

The boxplots and P values representing the derived parameters of endogenous displacements and strain in patients with and without clinically significant portal hypertension (≥ 10 mmHg). A: d_retro; B: µ_{ROI[0…10Hz, 2 cm × 2 cm]}; C: σ_{ROI[0…10Hz, 2 cm × 2 cm]}; D: µ_{ROI[0…10Hz, 1 cm × 1 cm]}. HVPG: Hepatic venous pressure gradient.

Figure 3

The boxplots and P values representing the derived parameters of endogenous displacements and strain in patients with and without severe portal hypertension (≥ 12 mmHg). A: d_retro; B: µ_{ROI[0…10Hz, 2 cm × 2 cm]}; C: σ_{ROI[0…10Hz, 2 cm × 2 cm]}; D: µ_{ROI[0…10Hz, 1 cm × 1 cm]}. HVPG: Hepatic venous pressure gradient.

Figure 4

Receiver operating characteristic curves of d_retro parameter for the diagnosis of portal hypertension. A: Receiver operating characteristic (ROC) curve for clinically significant portal hypertension [hepatic venous pressure gradient (HVPG) ≥ 10 mmHg]; B: ROC curve for severe portal hypertension (HVPG ≥ 12 mmHg).

Figure 5

Receiver operating characteristic curves of σ_{ROI[0–10Hz, 2 cm × 2 cm]} and µ_{ROI[0–10Hz, 1 cm × 1 cm]} parameters for the diagnosis of clinically significant portal hypertension (hepatic venous pressure gradient ≥ 10 mmHg).