FIBROSE HEPÁTICA AVALIADA POR ELASTOGRAFIA SHEAR WAVE-2D NO SEGUIMENTO DE PACIENTES TRANSPLANTADOS

FIBROSE HEPÁTICA AVALIADA POR ELASTOGRAFIA SHEAR WAVE-2D NO SEGUIMENTO DE PACIENTES TRANSPLANTADOS

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Andrine Vasconcelos Alves1;João Guilherme Bezerra Alves2; Bernardo Times de Carvalho3;Flávia Augusta de Orange Lins da Fonseca e Silva4

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​​ ¹Instituto de Medicina Integral Prof. Fernando Figueira (IMIP); Recife, Pernambuco, Brasil

[email protected]

​​ ²Instituto de Medicina Integral Prof. Fernando Figueira (IMIP); Recife, Pernambuco, Brasil

[email protected]

​​ ³Universidade Federal de Pernambuco (UFPE); Recife, Pernambuco, Brasil

[email protected]

⁴Instituto de Medicina Integral Prof. Fernando Figueira (IMIP); Recife, Pernambuco, Brasil

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RESUMO

A ocorrência de fibrose hepática no pós-transplante de fígado é uma preocupação frequente. Métodos não invasivos, como a elastografia hepática, apresentam boa acurácia para o diagnóstico de fibrose e vêm substituindo a biópsia hepática, método padrão ouro. Verificar a frequência, intensidade e fatores associados à fibrose hepática em pacientes pós-transplante, utilizando elastografia bidimensional por ondas de cisalhamento (2D-SWE). Estudo transversal que envolveu 52 pacientes, sobreviventes de transplante hepático. Transplantados por doença autoimune, aqueles com distúrbios vasculares e/ou biliares no pós-transplante e os transplantados com hepatite C que não foram tratados nos primeiros cinco anos após o transplante hepático foram excluídos. Foram estudados 52 pacientes e, de acordo com o 2D-SWE, 27 (51,9%) apresentavam fibrose significativa (≥F2) e 17 (32,7%) fibrose avançada (≥F3). A síndrome metabólica foi detectada em 23 (44,2%) dos pacientes, mas não houve associação estatística com a presença de fibrose hepática (p>0,05). Dislipidemia, sobrepeso ou obesidade e tempo de transplante acima de 5 anos foram associados à presença de fibrose significativa; p = 0,016; p= 0,017; p = 0,011, respectivamente. A presença de fibrose hepática pós-transplante detectada pelo 2D-SWE parece alta. Dislipidemia, sobrepeso/obesidade e tempo de transplante acima de 5 anos foram associados ao desenvolvimento de fibrose hepática pós-transplante.

Palavras-chaves: elasticidade hepática, fibrose hepática, transplante hepático, elastografia shear wave.

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LIVER FIBROSIS EVALUATED BY 2D-SHEAR WAVE ELASTOGRAPHY IN THE FOLLOW-UP OF LIVER TRANSPLANT PATIENTS

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ABSTRACT

​​ The occurrence of liver fibrosis in post-liver transplantation is a frequent concern. Non-invasive methods such as elastography, have good accuracy for the diagnosis of liver fibrosis and have been replacing liver biopsy, a gold standard method. To verify the frequency, intensity, and factors associated with liver fibrosis in post-transplant patients, using two-dimensional shear wave elastography (2D-SWE). Cross-sectional study enrolled 52 patients, survivors of liver transplant. Transplanted due to autoimmune disease, those with vascular and / or biliary disorders in the post-transplant, and those transplanted with hepatitis C who were not treated in the first five years after the liver transplant were excluded. 52 patients were studied and, according to the 2D-SWE, 27 (51.9%) had significant fibrosis (≥F2), and 17 (32.7%) advanced fibrosis (≥F3). Metabolic syndrome was detected in 23 (44.2%) of the patients, but there was no statistical association with the presence of liver fibrosis (p> 0.05). Dyslipidemia, overweight or obesity and transplant time above 5 years were associated with the presence of significant fibrosis; p=0.016; p=0.017; p=0.011, respectively. The presence of post-transplant liver fibrosis detected through 2D-SWE seems high. Dyslipidemia, overweight/obesity and transplantation time above 5 years were associated with the development of post-transplant liver fibrosis.

Key words: liver stiffness; liver fibrosis; liver transplant; shear wave elastography.

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1 INTRODUCTION

Liver transplantation has significantly increased life expectancy and is the reference treatment for endstage hepatic diseases [1,2]. However, after liver transplantation fibrosis may occur and has been associated with a poorer outcome, especially the presence of significant fibrosis [3]. Fibrosis progression is higher in liver transplants as compared to native livers [4]. Therefore, screening patients for fibrosis is essential in the follow-up of patients after hepatic transplantation.

Liver biopsy persists as a gold standard exam for the diagnosis of liver fibrosis. However, liver biopsy is an invasive procedure and can lead to complications as pain, hemobilia, bleedings, puncture of other viscera, or even death [5]. Moreover, insufficient sampling, and interobserver variability can occur [6]. ​​ Based on this, several noninvasive methods, especially imaging methods and serological biomarkers, have been proposed to detect and quantify fibrosis [7, 8]. Among the serological markers are the validated APRI and FIB-4. Elastography has been reported as a reference noninvasive imaging method [9, 10, 11]. Magnetic resonance elastography (MRE) is an accurate method for the diagnosis of hepatic fibrosis, however, cost and availability limit MRE use [12]. ​​ About ultrasound elastography, Two-dimensional shear wave elastography (2D-SWE) has been the technique most extensively studied for the evaluation of severe fibrosis [13]. However, 2D-SWE has have been almost exclusively studied in patients with native livers [14,15,16], and few studies have approached patients after liver transplantation [17]. The main objective of this study was to verify through 2D-SWE the frequency, intensity, and associated factors of liver fibrosis, in post-transplant patients.

2 PATIENTS AND METHODS

This cross sectional study evaluated liver transplant patients who have been transplanted between January 2008 and December 2018 at the Unit of Hepatic Transplantation, Hospital Universitário Oswaldo Cruz [Universitary Hospital Oswaldo Cruz] (HUOC). HUOC is reference for liver transplantation in Pernambuco state, Brazil, and currently perform around one hundred liver transplantations per year. This project was previously approved by the local ethics committee and all patients enrolled gave written informed consent.

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2.1 PATIENTS

 All transplanted patients in HUOC are systematically followed is scheduled at quarterly visits which includes physical examination and laboratory tests (blood count, transaminases, urea, creatinine, ionogram, alkaline phosphatase, γ-glutamyl transferase (GGT), bilirubins, and serum level of the immunosuppressant). Patients older than 18 years of age and regularly followed, i.e., at least two visit per year were enrolled in the study. ​​ Exclusion criteria were transplantation due to autoimmune disease, history of vascular and/or biliary disorders after transplantation and patients transplanted for hepatitis C who were not treated for at least 5 years after liver transplantation.

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2.2 METHODOS

 For each selected patient, some demographics (age, gender) and clinical characteristics (BMI, abdominal circumference, indication of liver transplantation, and time delay between liver transplantation and current evaluation) were recorded. Laboratory tests included complete blood count, aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase, γ-glutamyl transferase (GGT), and bilirubin - total and direct bilirubin. After the medical consultation, the patient performed hepatic elastography.

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3 LIVER FIBROSIS ANALYSIS BY SEROLOGICAL SCORES

FIB-4 was calculated using the formula age (years) × AST [U/l]/(platelets [109/l] × (ALT [U/l])1/2), in which the age of the patient was the age at the time of the 2D-SWE scan. APRI was calculated using the formula “AST/upper limit of normal]/platelet count [109/L]” × 100. The estimated evaluation of hepatic fibrosis using serological scores refers to the values: APRI ≥ 1.5 meaning significant fibrosis and FIB-4 ≥ 3.25, advanced fibrosis.

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4 LIVER FIBROSIS ANALYSIS BY ELASTOGRAPHY

All 2D-SWE measurements were performed at HUOC always by the same operator who is a member of the ultrasound team of the HUOC transplant service. The device used was the LOGIC E8-GE Heathcare with the 2D-shear-wave technique, and the values ​​were released in kPa. The measurement was performed on the right lobe of the liver, away from large blood vessels, biliary tracts, and at a distance of 2 to 4 cm from the liver capsule, with the choice of the region of interest (ROI). Patients were asked to hold a short neutral breath during the procedure. Ten measurements were performed and the final value was calculated as the median of these measurements.

 Two analyses of hepatic fibrosis were performed by ARFI elastography in which the result expressed in kPa is correlated with the degree of fibrosis. The first correlated the values of kPa, according to the guidelines of the manual of the device used (table 1), with histopathological score METAVIR: F0: absence of fibrosis, F1: minimal fibrosis, F2: significant fibrosis, F3: advanced fibrosis and F4: liver cirrhosis. Significant fibrosis is considered ≥F2 and advanced fibrosis ≥F3. ​​ Another analysis was using the cutoff point of 7 KpA, as suggested by the International Radiology Society, which states that values ​​below 7 KpA can rule out the presence of significant fibrosis ≥F2.

Table 01- Correlation of values in KpA by elastography 2D- shear wave ( LOGIC S8 2D-SWE) with METAVIR score

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5 STATISTICAL ANALYSIS

 Continuous variables were expressed as median (range) or means ± SD as appropriate. Categorical variables were expressed as count and percentage. The Gaussian distribution of the included variables was tested using the Kolmogorov–Smirnov test. After assessing the distribution normality, continuous variables were compared using the Student t-test, and analysis of variance or the Mann– Whitney U test when appropriate. Categorical variables were compared using the Chi-squared or Exact Fisher tests. Correlations were computed with Pearson’s correlation coefficient. The software SPSS 13.0 was used and a p value of ​​ 0.05 was considered significant.

6 RESULTS

52 patients were studied, with a mean age of 53 years (±13.61), and the majority being male (71.2%). Regarding the indication for transplantation, 14 (26.9%) patients were due to alcoholic cirrhosis, 10 (19.3%) were due to nonalcoholic steatohepatitis (NASH) (19.3%), 8 (15.4%) were due to hepatitis C, 6 (11.5%) were due to hepatitis B and for other indications, i.e iatrogenic lesion of bile duct, hemagioendothelioma, giant hemangioma, etc. Important to emphasize that there was no active viral disease in the selected patients.

Most patients had comorbidities, especially systemic hypertension and diabetes mellitus All patients currently denied alcoholism and/or smoking. Tacrolimus was used immunosuppressant by 42 (80.8%) patients and mycophenolate by 23 (44.2%) patients. Some patients used more than one immunosuppressive. Mycophenolato is not used on monotherapy.

Of the 52 patients, only 8 (15,4%) had elevated aminotransferase enzymes. Analysis through laboratory scores showed that 51/52 had an APRI value below 1.5 and 48 patients had an FIB-4 score below 3.5. The majority os patientes, 51.9%, presented significant fibrosis (≥F2) according to elastography, 32.7% with advanced fibrosis (≥ F3).

The time after transplant ranged from 2 to 11 years (6.6 ± 2.8 years). The kpA values ​​of elastography ranged from 4.29 kpA to 16.6 kpA, median 6.87kpA. (Table 2).

Liver enzymes values were not associated with liver fibrosis (p=0.70). Dyslipidemia and overweight or obesity were associated with significant fibrosis (p= 0.016 and p =0.017, respectively). Most patients had more than 5 years of transplantation (67%), and of these 64.7% had significant fibrosis, 13 of them (38.2%) with F4 fibrosis on elastography. The transplant time above 5 years was statistically relevant for the evolution to fibrosis (p = 0.011). (Table 2)

Table 2 – Comparison of patients' characteristics by stage of fibrosis

FK: tacrolimus ; MMF: Mycophenolate mofetil.; LT: liver transplant; NASH: Nonalcoholic steatohepatitis; HBV: Hepatitis B virus; HCV: Hepatitis C virus;

​​ (*)Chi-Square Test (**) Fisher's exact test ​​ 

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7 DISCUSSION

 Noninvasive methods to detect liver fibrosis has been a major challenge in post-liver transplantation patients, generally more susceptible to recurrent or de novo disease. In this study we detected liver fibrosis assessed with 2D-SWE, a recent technique of acoustic radiation force impulse (ARFI) that has shown a high accuracy in detecting fibrosis when compared to the gold standard, liver biopsy [18, 19]. In our sample, about half (51.9%) had significant fibrosis and most (32.7%) compatible with advanced fibrosis.

Few studies have evaluated SWE in post liver transplantation patients. Valente et al detected significant fibrosis in 58/196 (29%) transplant patients by 2D-SWE elastography [20]. Yoon et al mainly focused on rejection and hepatitis recurrence demonstrated that the liver stiffness in patient with rejection or recurrent hepatitis after liver graft was significantly higher than the liver recipients without rejection or hepatitis [21]. Yoon et al also found that liver stiffness was higher in the first four weeks after liver transplantation [21]. However we performed the elastography scan at minimal two years after liver transplantation. ​​ 

 Among the causes of fibrosis in post-transplant is viral reactivation as well as reactivation of the basic autoimmune disease. As we would like to exclude factors that can ​​ lead to the advancement of fibrosis independent of other factors, in order to avoid bias in the sample, we excluded patients with hepatitis C without early treatment in post-transplant and those transplanted with autoimmune hepatitis. Even with the exclusion of these patientes, our sample had a hig frequency of liver fibrosis, wich leads to other important causes of fibrosis in post transplant.

 The studied patients had a high prevalence of comorbidities especially ​​ the spectrum of metabolic syndrome (hypertension, diabetes, dyslipidemia and increased abdominal circumference), directly linked to the state of obesity and overweight. It was observed a frequency of 57.5% of metabolic syndrome, similar to other studies that have shown that metabolic syndrome is the most common complication in post-transplantation with a prevalence between 44% and 58%, being around 35% new cases after liver transplantation [22, 23].

 Another important finding was that the liver transplantation time longer than 5 years was associated for the presence of fibrosis. This may be due to the fact that, over the years, the patient has been under the effects of immunosuppressants for a longer time and is more prone to comorbidities, which contributes to their progression with more hepatic fibrosis. Liver fibrosis has been reported as common in patients with no clinical signs of graft deterioration [24].

 As highlighted in other studies, the level of aminotransferases is not always a good parameter to assess the presence of liver fibrosis. In our sample, only eight patients showed changes in liver enzyme levels, without association with liver fibrosis, according to the result of elastography. This fact may also have corroborated so that the APRI and FIB-4 scores were not associated with the diagnosis of liver fibrosis, since these scores use aminotransferase values ​​in their calculation. A retrospective study of 135 transplant patients undergoing liver biopsy, also did not show a good association between APRI and FIB-4 scores with liver fibrosis [25]. A systematic review conclude that elastography performs better to diagnose recurrent fibrosis in liver transplantation patients when compared to APRI and FIB-4, these serological markers can be used as an estimate of significant fibrosis at centers where elastography is not available [26]. ​​ 

 It is worth mentioning that elastography does not define the type of liver disease involved in fibrosis, which is only possible with clinical and histopathological analysis. However, better defining the patient to undergo such an invasive and risky procedure is of fundamental importance.

 Our study used one of the most recent techniques of ARFI elastography, 2D-SWE, which some studies show good accuracy in the assessment of liver fibrosis compared to biopsy [27-30]. In our sample, we observed a high frequency of significant hepatic fibrosis, which requires greater vigilance and intervention measures in order to prevent fibrosis progression, increased morbidity and mortality and even graft loss.

 In addition, the high prevalence of comorbidities in this population is an indication that more effective and interventional approaches are needed to better control the morbidity of these patients. Even more important, when we know that such comorbidities are intrinsically linked to Non-Alcoholic Fatty Liver Disease (NAFLD), currently, one of the main causes of the occurrence of fibrosis and indication for transplantation in the world.

 We also emphasize that in relation to patients transplanted for viral hepatitis, we include only those with hepatitis B with controlled viremia and those with hepatitis C treated in the first 5 years after transplantation, as it is known that persistent viremia in these cases may be a factor that competes for the occurrence and progression of fibrosis.

 There are still few studies using elastography to follow-up liver post-transplant patients. Our study used an excellent non-invasive method, 2D-SWE elastography, and clinical laboratory analysis of transplant patients for various causes. We did not find a similar study in our literature review. As a limitation we had the small number of the sample and the impossibility of performing a liver biopsy in our sample due to risks and because it is not routine in the service. However, 2D-SWE has been described as a reliable and reproducible method to assess liver stiffness measurement with good diagnostic accuracy to assess liver fibrosis [16].

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8 CONCLUSION

 This study revealed a high frequency of liver fibrosis through elastography and its relationship with dyslipidemia and overweight/obesity in patients after late liver transplantation. These comorbidities are known to be related to NAFLD, constituting a risk factor for the occurrence of fibrosis, which increases morbidity and mortality of transplanted patients. In addition, the study showed that patients with transplant time over 5 years had more significant fibrosis.A more careful analysis of these patients is important.

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