Noninvasive acoustic radiation force impulse (ARFI) elastography for assessing the severity of fibrosis in the post-operative patients with biliary atresia

Effectiveness of two-dimensional shear-wave sonoelastography in the diagnosis and follow-up of infantile hypertrophic pyloric stenosis

INTRODUCTION

We sought to determine the effectiveness and utility of two-dimensional shear-wave sonoelastography (2D-SW-SE) in the diagnosis and postoperative follow-up of infantile hypertrophic pyloric stenosis (IHPS).

MATERIALS AND METHODS

Twenty-three infants were included in the study, 13 in the IHPS group and 10 in the control group (CG). Preoperative B-mode ultrasonography measurements (longitudinal length and single-wall thickness of the pylorus) and 2D-SW-SE measurements (pylorus tissue stiffness and shear-wave propagation speed) were compared between the groups. The infants with IHPS then underwent Ramstedt pyloromyotomy and were invited for follow-ups on the tenth day and the first, third, and sixth months postoperatively. Measurements taken at the follow-ups were compared with the preoperative values.

RESULTS

No differences were found between the groups regarding age, gender, body weight, or week of birth. The pyloric lengths in the IHPS group were longer than in the CG (p < 0.001), and the single-wall thicknesses were thicker (p < 0.001). The pylorus in the IHPS group was four times stiffer than in the CG (27.4 kPa versus 7.66 kPa), and the shear-wave propagation speed in the tissue was higher (1.34 m/s versus 2.69 m/s; p < 0.001). Both values decreased over time in the IHPS group and were normal by the third postoperative month.

CONCLUSIONS

2D-SW-SE can be used as an assistive imaging tool alongside B-mode ultrasound for diagnosing IHPS. It can also be used to identify inadequate surgery by detecting whether the pyloric tissue has softened at follow-up.

Ultrasound elastography in the diagnosis of biliary atresia in pediatric surgery: a systematic review and meta-analysis of diagnostic test

BACKGROUND

Biliary atresia (BA) is one of the most fatal hepatobiliary diseases in infants and young children, and is easy to cause obstructive jaundice in infants and children, and liver transplantation in children. BA and infantile hepatitis syndrome are the main causes of cholestatic jaundice. The early clinical manifestations are extremely similar, and timely identification is difficult. Therefore, early and differential diagnosis of BA is crucial. At present, there are many imaging diagnosis methods for BA, such as ultrasound examination and nuclear magnetic resonance. Ultrasound elastography (USE) is the most popular method. However, the application of USE in BA is still in the exploratory stage.

METHODS

PubMed, Web of Science, Embase, Cochrane Library, and other databases were searched for articles on USE diagnosis of pediatric surgical BA. Later, the articles were screened, and the included articles should meet the following requirements: the research objects were children with BA; the intervention measures were USE diagnosis; the control group was diagnosed by other methods than USE. RevMan5.3 was adopted for quality assessment, and forest maps and summary receiver operating characteristic (SROC) curves were constructed.

RESULTS

Finally, seven articles covering 490 patients were included. There were 120 patients in the control group. The included articles showed good quality and there was no obvious bias. The area under the SROC curve (AUC) for USE diagnosis of BA was 0.93, the sensitivity was 0.93 (95% CI: 0.72-1.00), and the specificity was 0.95 (95% CI: 0.74-1.00).

DISCUSSION

USE showed high diagnostic value for pediatric surgical biliary tract closure.

Ultrasound shear wave elastography: does it add value to gray-scale ultrasound imaging in differentiating biliary atresia from other causes of neonatal jaundice?

BACKGROUND

Neonatal/infantile jaundice is relatively common, and most cases resolve spontaneously. However, in the setting of unresolved neonatal cholestasis, a prompt and accurate assessment for biliary atresia is vital to prevent poor outcomes.

OBJECTIVE

To determine whether shear wave elastography (SWE) alone or combined with gray-scale imaging improves the diagnostic performance of US in discriminating biliary atresia from other causes of neonatal jaundice over that of gray-scale imaging alone.

MATERIALS AND METHODS

Infants referred for cholestatic jaundice were assessed with SWE and gray-scale US. On gray-scale US, two radiology readers assessed liver heterogeneity, presence of the triangular cord sign, hepatic artery size, presence/absence of common bile duct and gallbladder, and gallbladder shape; associated interobserver correlation coefficients (ICC) were calculated. SWE speeds were performed on a Siemens S3000 using 6C2 and 9 L4 transducers with both point and two-dimensional (2-D) SWE US. Both univariable and multivariable analyses were performed, as were receiver operating characteristic curves (ROC) and statistical significance tests (chi-squared, analysis of variance, t-test and Wilcoxon rank sum) when appropriate.

RESULTS

There were 212 infants with biliary atresia and 106 without biliary atresia. The median shear wave speed (SWS) for biliary atresia cases was significantly higher (P<0.001) than for non-biliary-atresia cases for all acquisition modes. For reference, the median L9 point SWS was 2.1 m/s (interquartile range [IQR] 1.7-2.4 m/s) in infants with biliary atresia and 1.5 m/s (IQR 1.3-1.9 m/s) in infants without biliary atresia (P<0.001). All gray-scale US findings were significantly different between biliary-atresia and non-biliary-atresia cohorts (P<0.001), intraclass correlation coefficient (ICC) range 0.7-1.0. Triangular cord sign was most predictive of biliary atresia independent of other gray-scale findings or SWS - 96% specific and 88% sensitive. Multistep univariable/multivariable analysis of both gray-scale findings and SWE resulted in three groups being predictive of biliary atresia likelihood. Abnormal common bile duct/gallbladder and enlarged hepatic artery were highly predictive of biliary atresia independent of SWS (100% for girls and 95-100% for boys). Presence of both the common bile duct and the gallbladder along with a normal hepatic artery usually excluded biliary atresia independent of SWS. Other gray-scale combinations were equivocal, and including SWE improved discrimination between biliary-atresia and non-biliary-atresia cases.

CONCLUSION

Shear wave elastography independent of gray-scale US significantly differentiated biliary-atresia from non-biliary-atresia cases. However, gray-scale findings were more predictive of biliary atresia than elastography. SWE was useful for differentiating biliary-atresia from non-biliary-atresia cases in the setting of equivocal gray-scale findings.

Hepatic subcapsular or capsular flow in biliary atresia: is it useful imaging feature after the Kasai operation?

OBJECTIVES

To evaluate the implications of hepatic subcapsular and capsular flows using ultrasonography (US) in children after Kasai operation.

METHODS

Children who underwent liver US including color Doppler US and microvascular imaging (MVI) from May 2017 to October 2017 were retrospectively included. Children who underwent the Kasai operation for biliary atresia were included in the Kasai group and children with normal liver were included in the control group. Using US results, the number of intrahepatic biliary cysts and the maximum diameter of the spleen were evaluated in the Kasai group. Liver stiffness values were included when patients in the Kasai group had transient elastography (TE) or shear wave elastography (SWE) results. Hepatic subcapsular and capsular flows on color Doppler US and MVI were compared between the two groups using the following scores: 0, no flow reaching the hepatic capsule; 1, any flow reaching the hepatic capsule; and 2, contiguous hepatic capsular flow. The logistic regression test was used to identify associations between age, intrahepatic biliary cysts, spleen size, SWV, TE results, and flow scores measured on Doppler US and MVI in the Kasai group using the odds ratio (OR) and 95% confidence interval (CI).

RESULT

A total of 65 children (mean 7.6 ± 5.3 years), 44 in the Kasai group and 21 in the control group, were included. In the control group, one child had score 1 on MVI and others had score 0 on both Doppler US and MVI. Among the Kasai group, 28 children (63.6%) had score 1, while others had score 0 using Doppler US. Using MVI, 24 children (54.5%) had score 2, 18 children had score 1, and one child had score 0. In the Kasai group, increased liver stiffness on TE was the only factor significantly associated with the presence of subcapsular flow on color Doppler US (OR 1.225, 95% CI 1.020-1.470) and increased spleen size was the only factor significantly associated with increased flow scores on MVI (OR 1.397, 95% CI 1.002-2.724).

CONCLUSION

Detection of hepatic subcapsular, capsular flows on US would be meaningful for children after receiving the Kasai operation.

KEY POINTS

• Hepatic subcapsular or capsular flows can be useful not only for the diagnosis but also for the postoperative follow-up in patients with biliary atresia. • Increased liver stiffness and splenomegaly after the Kasai operation were associated with presence of subcapsular or capsular flow on ultrasonography. • Evaluation of hepatic subcapsular and capsular flows could be needed to assess disease progression after receiving the Kasai operation.

Normal values of shear wave velocity in liver tissue of healthy children measured using the latest acoustic radiation force impulse technology

BACKGROUND

Several studies have demonstrated the feasibility and effectiveness of using ultrasound elastography to assess liver tissue stiffness. Virtual touch imaging quantification (VTIQ) based on acoustic radiation force impulse imaging has been developed as a latest and noninvasive method for assessing liver stiffness in children.

AIM

To determine the standard value in healthy children, and to identify possible factors that might influence the VTIQ measurement.

METHODS

With the ethical approval, 202 children between 1 month and 15 years old were included in this study. None of them had any liver or systematic diseases. All children had a normal ultrasound scan and normal body mass index (BMI) range. The subjects were divided into four age and BMI groups. The effects of gender, age, liver lobe, measurement depth, and BMI on liver elasticity were investigated.

RESULTS

A significant correlation was found between age and shear wave velocity (SWV) value. At measurement depths of 1.5 cm and 2.0 cm in the left lobe, there were significant differences among the age groups. SWV values were significantly negatively correlated with the measurement depth. Gender, liver lobe, and BMI showed no significant effect on the SWV values. Age and BMI may influence the quality of the elastogram.

CONCLUSION

VTIQ is a noninvasive technique that is feasible to measure liver stiffness in children. The afore-mentioned velocity value obtained utilizing VTIQ method could be used as reference value for normal liver stiffness in children.

Predicting gastroesophageal varices through spleen magnetic resonance elastography in pediatric liver fibrosis

BACKGROUND

A recent retrospective study confirmed that hepatic stiffness and splenic stiffness measured with magnetic resonance elastography (MRE) are strongly associated with the presence of esophageal varices. In addition, strong correlations have been reported between splenic stiffness values measured with MRE and hepatic venous pressure gradients in animal models. However, most studies have been conducted on adult populations, and previous pediatric MRE studies have only demonstrated the feasibility of MRE in pediatric populations, while the actual clinical application of spleen MRE has been limited.

AIM

To assess the utility of splenic stiffness measurements by MRE to predict gastroesophageal varices in children.

METHODS

We retrospectively reviewed abdominal MRE images taken on a 3T system in pediatric patients. Patients who had undergone Kasai operations for biliary atresia were selected for the Kasai group, and patients with normal livers and spleens were selected for the control group. Two-dimensional spin-echo echo-planar MRE acquisition centered on the liver, with a pneumatic driver at 60 Hz and a low amplitude, was performed to obtain hepatic and splenic stiffness values. Laboratory results for aspartate aminotransferase to platelet ratio index (APRI) were evaluated within six months of MRE, and the normalized spleen size ratio was determined with the upper normal size limit. All Kasai group patients underwent gastroesophageal endoscopy during routine follow-up. The Mann-Whitney U test, Kendall's tau b correlation and diagnostic performance analysis using the area under the curve (AUC) were performed for statistical analysis.

RESULTS

The median spleen MRE value was 5.5 kPa in the control group (n = 9, age 9-18 years, range 4.7-6.4 kPa) and 8.6 kPa in the Kasai group (n = 22, age 4-18 years, range 5.0-17.8 kPa). In the Kasai group, the APRI, spleen size ratio and spleen MRE values were higher in patients with portal hypertension (n = 11) than in patients without (n = 11) (all P < 0.001) and in patients with gastroesophageal varices (n = 6) than in patients without (n = 16) (all P < 0.05), even though their liver MRE values were not different. The APRI (τ = 0.477, P = 0.007), spleen size ratio (τ = 0.401, P = 0.024) and spleen MRE values (τ = 0.426, P = 0.016) also correlated with varices grades. The AUC in predicting gastroesophageal varices was 0.844 at a cut-off of 0.65 (100% sensitivity and 75% specificity) for the APRI, and 0.844 at a cut-off of 9.9 kPa (83.3% sensitivity and 81.3% specificity) for spleen MRE values.

CONCLUSION

At a cut-off of 9.9 kPa, spleen MRE values predicted gastroesophageal varices as well as the APRI and spleen size ratio in biliary atresia patients after the Kasai operation. However, liver MRE values were not useful for this purpose.

Evaluation of elastography combined with serological indexes for hepatic fibrosis in patients with chronic hepatitis B

AIM

To investigate the value of ultrasound elastography combined with serological indexes in diagnosing liver fibrosis and assessing its severity.

METHODS

A total of 338 chronic hepatitis B (CHB) patients were divided into a disease group (patients with hepatic fibrosis) and control group (subjects without hepatic fibrosis). The disease group was further divided into S1-S4 according to the degree of fibrosis. Independent risk factors for hepatic fibrosis were analyzed using multivariate logistic regression. The diagnostic values of hepatic fibrosis from different indicators were compared using receiver operating characteristic (ROC) curves. The combination of elastography and serological indexes was explored to assess the severity of hepatic fibrosis.

RESULTS

The multivariate logistic regression analysis results revealed that shear wave velocity (SWV), hyaluronic acid (HA), type IV collagen (CIV) and aspartate aminotransferase-to-platelet ratio index (APRI) significantly affected the occurrence of hepatic fibrosis. The ROC curve revealed that the accuracy of the diagnosis of hepatic fibrosis for SWV and HA were 87.3% and 84.8%, respectively. The accuracy of SWV combined with HA was 88.9%. The multiple linear regression analysis revealed that SWV, aspartate aminotransferase (AST)/alanine aminotransferase (ALT), HA, CIV, APRI and fibrosis index based on the 4 factor (FIB-4) were screened as statistically significant independent factors. The established regression equation was: Fibrosis level = -4.046 + 1.024 × SWV + 1.170 × AST/ALT + 0.011 × HA + 0.020 × CIV + 0.719 × APRI + 0.379 × FIB-4.

CONCLUSION

SWV combined with serological indexes can improve the accuracy of diagnosis for CHB hepatic fibrosis. Serum indexes can help diagnose the degree of hepatic fibrosis.

Evaluation of Liver, Kidney, and Spleen Elasticity in Healthy Newborns and Infants Using Shear Wave Elastography

OBJECTIVES

Elasticity measurements of tissues can be valuable in the diagnosis and management of various diseases. The aim of this study was to determine the elasticity values for normal liver, kidney, and spleen of healthy newborns and infants using shear wave elastography (SWE) imaging.

METHODS

A total of 50 healthy term newborns and infants (19 girls and 31 boys; mean age 20.1 days, range 1 to 70 days) were examined by an experienced pediatric radiologist using SWE. None of them had any liver, kidney or spleen disease, or any other systemic disease that could affect these organs secondarily. All newborns and infants had a normal abdominal ultrasound scan.

RESULTS

Age, sex, weight, height, and body mass index had no significant effects on shear wave velocity (SWV) values of liver and spleen. The SWV values of both kidneys decreased with age, weight, height, and body mass index. The mean SWV values were 1.70 m/s (range: 1.23-2.43 m/s) for the liver, 1.69 m/s (range: 0.8-2.40 m/s) for the right kidney, 1.70 m/s (range: 0.9-2.49 m/s) for the left kidney, and 2.03 m/s (range: 1.28-2.48 m/s) for the spleen.

CONCLUSIONS

Shear wave elastography can be used to measure liver, kidney, and spleen elasticity in newborns and infants. The standard values for abdominal organs allow differentiation of healthy versus pathological tissue. We measured the normal values of SWE in healthy newborns and infants as reference data.

Acoustic Radiation Force Impulse Imaging for Assessing Liver Fibrosis Preoperatively in Infants With Biliary Atresia: Comparison With Liver Fibrosis Biopsy Pathology

OBJECTIVES

The purpose of this study was to investigate the diagnostic performance of acoustic radiation force impulse (ARFI) in assessing liver fibrosis preoperatively in infants with biliary atresia (BA).

METHODS

A total of 50 consecutive infants with BA and 50 healthy infants who underwent ARFI examination were recruited. Siemens Acuson S2000 in Virtual Touch Quantification mode (Siemens Medical Solutions, Mountain View, CA) was used to measure shear wave speeds (SWSs). All infants with BA underwent a liver biopsy within 3 days after ARFI imaging. The liver fibrosis stages of specimens were defined according to the Batts-Ludwig scoring system. The correlation analysis was performed between SWSs and pathological findings. Cut-off values were determined using receiver operating characteristic (ROC) curves.

RESULTS

The mean SWS in the BA group was significantly higher than controls (mean ± standard deviation): 1.89 ± 0.45 versus 1.12 ± 0.06 m/s; P < .001). A significant correlation was found between the SWSs and fibrosis stages (r = 0.719, P < .001). The cut-off value for predicting significant fibrosis (F ≥ 2), severe fibrosis (F ≥ 3), and cirrhosis (F = 4) was 1.53, 1.80 and 2.16 m/s, respectively, and the area under the ROC curve was 0.823, 0.884 and 0.917, respectively.

CONCLUSIONS

Acoustic radiation force impulse imaging showed significant correlation with the severity of liver fibrosis by comparing it with liver fibrosis biopsy pathology. It may be an effective method for liver fibrosis assessment, prognosis prediction, and clinical management in infants with BA.

Limitations and opportunities of non-invasive liver stiffness measurement in children

Changes in liver structure are an important issue in chronic hepatopathies. Until the end of the 20^th century, these changes could only be determined by histological analyses of a liver specimen obtained via biopsy. The well-known limitations of this technique (i.e., pain, bleeding and the need for sedation) have precluded its routine use in follow-up of patients with liver diseases. However, the introduction of non-invasive technologies, such as ultrasound and magnetic resonance imaging, for measurement of liver stiffness as an indirect marker of fibroses has changed this situation. Today, several non-invasive tools are available to physicians to estimate the degree of liver fibrosis by analysing liver stiffness. This review describes the currently available tools for liver stiffness determination that are applicable to follow-up of liver fibrosis/cirrhosis with established clinical use in children, and discusses their features in comparison to the “historical” tools.

Supersonic shearwave elastography in the assessment of liver fibrosis for postoperative patients with biliary atresia

To explore an effective noninvasive tool for monitoring liver fibrosis of children with biliary atresia (BA) is important but evidences are limited. This study is to investigate the predictive accuracy of supersonic shearwave elastography (SSWE) in liver fibrosis for postoperative patients with BA and to compare it with aspartate aminotransferase to platelet ratio index (APRI) and fibrosis-4 (FIB-4). 24 patients with BA received SSWE and laboratory tests before scheduled for liver biopsy. Spearman rank coefficient and receiver operating characteristic (ROC) were used to analyze data. Metavir scores were F0 in 3, F1 in 2, F2 in 4, F3 in 7 and F4 in 8 patients. FIB-4 failed to correlate with fibrosis stage. The areas under the ROC curves of SSWE, APRI and their combination were 0.79, 0.65 and 0.78 for significant fibrosis, 0.81, 0.64 and 0.76 for advanced fibrosis, 0.82, 0.56 and 0.84 for cirrhosis. SSWE values at biopsy was correlated with platelet count (r = -0.426, P = 0.038), serum albumin (r = -0.670, P < 0.001), total bilirubin (r = 0.419, P = 0.041) and direct bilirubin levels (r = 0.518, P = 0.010) measured at 6 months after liver biopsy. Our results indicate that SSWE is a more promising tool to assess liver fibrosis than APRI and FIB-4 in children with BA.

Acoustic radiation force impulse sonography in assessing children with biliary atresia for liver transplantation

BACKGROUND

Children with biliary atresia are prone to developing progressive hepatic fibrosis and biliary cirrhosis following the Kasai operation. The only treatment is liver transplantation.

OBJECTIVE

To assess liver fibrosis by acoustic radiation force impulse elastography (ARFI) in children who had Kasai operation, with the goal of identifying an ARFI value cut-off for children requiring liver transplantation.

MATERIALS AND METHODS

Of the 32 post-Kasai children included, 19 were transplanted or listed for transplantation (group A), while 13 were not on the list during their follow-up (group B). We recorded biopsies, blood samples and ARFI values over time, including at Kasai operation and at transplantation. We estimated an association between groups and continuous variables using generalized estimating equations, and we compared categorical variables using the Fisher exact test.

RESULTS

Portal hypertension signs were similar in both groups, whereas ARFI values were higher in group A (mean±standard deviation=3.3±1.2 m/s) than in group B (2.0±0.7 m/s; P=.0003). Eighteen of 19 (94.7%) children in group A and 6/13 (46.2%) children in group B presented with two consecutive ARFI values ≥2 m/s (sensitivity=7%, specificity=53.8%; P=0.003).

CONCLUSION

We found that children who were transplanted had two consecutive ARFI values ≥2 m/s during follow-up. ARFI for evaluation of post-Kasai liver fibrosis may assist the long-term assessment of biliary atresia and may even guide treatment decisions.

Ultrasound shear wave speed measurements correlate with liver fibrosis in children

BACKGROUND

Little published research has shown the relationship between noninvasive US shear wave speed (SWS) measurements and degree of liver fibrosis as established by percutaneous biopsy in children.

OBJECTIVE

To assess the relationship between liver US shear wave speed (SWS) measurements and parenchymal fibrosis in children.

MATERIALS AND METHODS

Sixty-two children (0-18 years old) with known or suspected liver disease underwent same-day US shear wave elastography (SWE) and clinically ordered percutaneous core needle biopsy. SWE was performed just before the liver biopsy in the area targeted for sampling, using an Acuson S3000 US system with a 9L4 transducer; six SWS measurements were acquired using Virtual Touch Quantification (VTQ) and Virtual Touch IQ (VTIQ) modes. Biopsy specimens were scored for histological fibrosis and inflammation. Bivariate relationships were assessed using Pearson correlation, while multiple linear regression analysis was used to establish the relationship between SWS and predictor variables. Receiver operating characteristic (ROC) curves were created to assess the abilities of VTQ and VTIQ to discern low vs. high liver fibrosis (histological fibrosis scores 0-2 vs. 3-6).

RESULTS

There were significant positive correlations between liver histological fibrosis score and VTQ (n = 49) and VTIQ (n = 48) mean shear wave speed measurements (r = 0.68 and r = 0.73; P-values <0.0001). There also were significant positive correlations between liver histological inflammation score and VTQ and VTIQ mean shear wave speed measurements (r = 0.47 and r = 0.44, and P = 0.0006 and P = 0.0016, respectively). For VTQ, both histological fibrosis (P < 0.0001) and inflammation (P = 0.04) scores were significant predictors of shear wave speed (model adjusted R (2) = 0.49). For VTIQ, only histological fibrosis score (P < 0.0001) was a significant predictor of shear wave speed (model adjusted R (2) = 0.56). ROC areas under the curve were 0.84 and 0.86 for VTQ and VTIQ, respectively.

CONCLUSION

Liver US shear wave speed measurements increase with increasing parenchymal fibrosis in children.

Hepatic ADC map as an adjunct to conventional abdominal MRI to evaluate hepatic fibrotic and clinical cirrhotic severity in biliary atresia patients

OBJECTIVES

Hepatic apparent diffusion coefficient (ADC) values and ADC-related indices were correlated with the Mayo risk score for primary biliary cirrhosis (MRSPBC) and METAVIR scores of liver specimens to determine the clinical and pathological significance of diffusion-weighted magnetic resonance imaging (DWMRI).

METHODS

Thirty-two patients with biliary atresia (BA; mean age 461 days, range 11-4616 days) received magnetic resonance examinations from March 2009 to August 2013. A free-breathing DWMRI sequence was performed with the single-shot echo-planar imaging technique with b = 0 and 500 s/mm(2) in all 32 BA patients and 24 controls. We used the ordinal logistic regression test and Spearman rank correlation test to analyse the relationships between the MRSPBC and METAVIR fibrosis scores and right liver-to-psoas ADC ratios (LTPARs).

RESULTS

BA patients had significantly lower LTPARs in both hepatic lobes than controls (p < 0.01). Right LTPARs, showing moderate intraobserver agreement (intraclass correlation coefficient = 0.736) and interobserver reliability (intraclass correlation coefficient = 0.659), were negatively correlated with MRSPBC and METAVIR fibrosis scores (R(2) = 0.398, p = 0.024 and R(2) = 0.628, p < 0.001, respectively).

CONCLUSION

Right LTPARs may be used for long-term follow-up of cirrhosis severity in BA patients.

KEY POINTS

• Hepatic ADC values by DWI correlates well with clinical/pathologic fibrosis scores • Periodic, non-invasive, quantitative imaging follow-up of patients with biliary cirrhosis is feasible • Information on cirrhosis severity could help decide on management options in children with BA • ADC values may be useful in this regard.

Spleen stiffness measurements by acoustic radiation force impulse imaging after living donor liver transplantation in children: a potential quantitative index for venous complications

BACKGROUND

Living donor liver transplantation in children often results in venous complications, leading to portal hypertension. Spleen stiffness measurements have been recently proposed as a new, noninvasive parameter for portal hypertension in cirrhotic patients.

OBJECTIVE

To evaluate the diagnostic value of spleen stiffness measurements by acoustic radiation force impulse (ARFI) imaging in diagnosing venous complications after pediatric living donor liver transplantation.

MATERIALS AND METHODS

We prospectively enrolled 69 patients after pediatric living donor liver transplantation using a left-side liver allograft. Around the time of the protocol liver biopsy examination, spleen stiffness measurements by ARFI imaging were performed via the left intercostal space at the center of the spleen parenchyma and repeated five times. Imaging examinations around the time of the spleen stiffness measurements were retrospectively reviewed. Regarding venous complications, significant portal and hepatic venous stenosis was defined as >50% stenosis on multiphasic computed tomography.

RESULTS

After post hoc exclusion, 62 patients were studied. Portal and hepatic venous stenosis was identified in three and two patients, respectively. The median spleen stiffness values were 2.70 and 4.00 m/s in patients without and with venous complications, respectively (P < 0.001). Spleen stiffness measurements showed good diagnostic power for venous complications, and the cutoff value was determined as 2.93 m/s, with 100% sensitivity and 78.9% specificity. Spleen stiffness measurements decreased with the relief of venous stenosis resulting from an interventional radiology procedure.

CONCLUSION

Spleen stiffness measurements by ARFI imaging might provide a useful quantitative index for venous complications after pediatric living donor liver transplantation.

Shear wave elastography helps differentiate biliary atresia from other neonatal/infantile liver diseases

BACKGROUND

Biliary atresia is a rapidly progressive liver disease necessitating prompt diagnosis and surgical intervention, so it must be promptly distinguished from other neonatal/infantile liver diseases.

OBJECTIVE

To determine whether US shear wave elastography (SWE) can differentiate biliary atresia from other neonatal/infantile liver diseases based on liver hardness.

MATERIALS AND METHODS

Eleven children younger than 1 year who had suspected liver disease underwent anatomically and temporally-related hepatic shear wave elastography and clinically indicated percutaneous core needle biopsy. Shear wave elastography was performed immediately prior to liver biopsy at the targeted biopsy site using an Acuson S3000 US system/9L4 transducer (Siemens Medical Solutions USA, Malvern, PA). Shear wave elastography was performed using Virtual Touch Quantification (VTQ) and Virtual Touch IQ (VTIQ) modes, and six shear wave speed measurements were acquired from each subject for each mode. Children were placed in two groups based on histology, biliary atresia (n = 6) vs. non-biliary atresia (other neonatal/infantile liver diseases) (n = 5), and mean shear wave speed measurements were compared using the unpaired student's t-test (two-tailed). A P-value <0.05 was considered significant.

RESULTS

Using the VTQ mode, mean liver shear wave speed was 2.08 ± 0.17 m/s for the biliary atresia group and 1.28 ± 0.13 m/s for the non-biliary atresia group (P < 0.0001). Using the VTIQ mode, mean liver shear wave speed was 3.14 ± 0.73 m/s for the biliary atresia group and 1.61 ± 0.23 m/s for the non-biliary atresia group (P = 0.003). Ishak liver fibrosis scores ranged from 3 to 6 for the biliary atresia group and from 0 to 1 for the non-biliary atresia group.

CONCLUSION

Liver shear wave speed is abnormally increased in neonates and infants with biliary atresia.

Comparison of acoustic radiation force impulse/serum noninvasive markers for fibrosis prediction in liver transplant

OBJECTIVES

Fibrosis, related to several causes, can be diagnosed in children and adolescents' liver grafts that are >1 year old. At present, liver biopsy is the gold standard for assessing liver damage in the posttransplant setting. We aimed to evaluate the accuracy of noninvasive biomarkers of fibrosis, namely, acoustic radiation force impulse (ARFI), aspartate-to-platelet ratio index, and aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio index, either alone or in combination, for predicting fibrosis in pediatric patients submitted to liver transplantation.

METHODS

We prospectively assessed liver fibrosis in 30 children/adolescents with liver transplant through biopsy (liver transplant follow-up during 12 months). ARFI with Virtual Touch Software (Acuson 2000) was performed, and blood samples were taken to determine liver function and platelet count. Two groups were analyzed according to the histopathologic stage of fibrosis, namely, none/mild (F0-F1) versus significant fibrosis (F2-4).

RESULTS

The mean age of the 30 patients was 11 years (3-18 years), with a mean posttransplant period of assessment of 6.5 years. Twenty-four patients (80%) presented stage F0-F1 fibrosis and 6 patients (20%) presented stage F2-4. The area under the curve using receiver operating characteristic analysis for ARFI, aspartate-to-platelet ratio index, and AST/ALT ratio index for significant fibrosis was 0.76 (P = 0.052), 0.74 (P = 0.066), and 0.69 (P = 0.162), respectively. Through multivariate logistic regression analysis, the only independent predictor of significant fibrosis was ARFI (odds ratio 10.7, 95% confidence interval 1.2-95.7; P = 0.045). The combination of ARFI and AST/ALT ratio index presented a good diagnostic accuracy of fibrosis (area under the curve of 0.83; P = 0.013).

CONCLUSIONS

ARFI may serve as a potential method for assessing significant fibrosis in pediatric patients with liver transplant, particularly in combination with AST/ALT ratio index.

Elastography for hepato-biliary-pancreatic surgery

Palpation is a subjective and non-sharable diagnostic method. Recently, palpation has been supported and replaced by elastography, which provides a novel parameter of “stiffness” as a visual representation or quantified value. Today, elastography is performed using two major modalities: strain elastography and shear wave elastography. Strain elastography converts the extent of deformation during external compression into colors, displaying these colors as a strain map in a motion picture representing the relative elasticity inside the region of interest. Shear wave elastography can quantify the elasticity of a target by calculating the velocity of shear waves generated by a probe. In addition to superficial organs, elastography has also been applied to upper abdominal organs, including the liver, pancreas and spleen. The visualization of the stiffness of focal lesions in the liver or the pancreas has enabled a more sensitive and specific depiction of small, non-palpable nodules, which are difficult to depict using B-mode ultrasonography. The quantification of stiffness also enables non-invasive estimates of liver fibrosis, the risk of postoperative liver insufficiency and the risk of recurrence of viral hepatitis after transplantation. In this article, we review the major reports that have recently been published describing the effective application of elastography to solid upper abdominal organs in a clinical setting.