British Journal of Radiology (2005) 78, 189-197
© 2005 British Institute of Radiology
doi: 10.1259/bjr/75208448
Ultrasound evaluation of the fibrosis stage in chronic liver disease by the simultaneous use of low and high frequency probes
T Nishiura, RMS
1
H Watanabe, RMS
1
M Ito, MD
1,2
Y Matsuoka, MD
3
K Yano, MD
4
M Daikoku, MD
4
H Yatsuhashi, MD
4
K Dohmen, MD, FACP, SJSUM
4 and
H Ishibashi, MD, FACP, SJSUM
4
1 Clinical Laboratory, 2 Department of Pathology, 3 Deartment of Radiology and 4 Clinical Research Centre, NHO National Nagasaki Medical Centre, Omura, Nagasaki, 856-8562 Japan
Correspondence: Dr Koji Yano, Clinical Research Centre, NHO National Nagasaki Medical Centre, Kubara 2-1001-1 Omura, Nagasaki 856-8562 Japan
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Abstract
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A liver biopsy is currently considered the definitive diagnostic modality for establishing the severity of hepatic fibrosis. We analysed the diagnostic sensitivity and accuracy of ultrasound (US) using both low frequency and high frequency probes as a repeatable, inexpensive, and reliable method to determine the fibrosis stage in chronic liver disease and then compared our results with the histological findings. A total of 103 patients with chronic liver disease (60 males and 43 females, average age 51 years old) who had undergone both a liver biopsy and US with 2–5 MHz frequency and 5–12 MHz frequency probes were prospectively evaluated in this study. An US scoring system using both the low frequency and high frequency probes was performed by evaluating the edge, surface and parenchymal texture of the liver. Each score was obtained by evaluating three parameters; the bluntness of the liver edge, the irregularity of the surface and the coarseness of the parenchymal texture were evaluated and then compared with the histological findings. The US scores of the liver edge (rs: 0.6668), liver surface (rs: 0.9007) and liver parenchymal texture (rs: 0.8853) correlated significantly with the fibrosis stage obtained based on the biopsy findings. The accumulated US scores of these three parameters, however, was found to be the most reliable indicator (rs: 0.9524). Patients with an accumulated score of 6.5 or more were all found to have fibrosis stage 4 in which the accuracy of our scoring system for correctly predicting cirrhosis was found to be 100% sensitive. When an accumulated US score of 3 was interpreted to indicate mild fibrosis (a fibrosis score of 0 or 1), all 42 patients with stage 0 or 1 fibrosis were found to have an accumulated US score of 3 or less (a probability of 100%) and 42 of 53 patients with a score of 3 or less were found to have stage 0 or 1 fibrosis (specificity of 79.2%). An ultrasound evaluation of the liver fibrosis stage based on the scoring system using both low and high frequency probes was found to be a reliable and effective alternative to the histological staging in chronic liver diseases.
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Introduction
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The liver fibrosis stage in patients with chronic liver diseases due to an infection with hepatitis B virus (HBV) or C virus (HCV) is a pivotal factor regarding both the therapeutic options and for predicting the prognosis. A liver biopsy is considered to be the gold standard for diagnosing the liver fibrosis stage and predicting the outcome of the diseases. Although a percutaneous liver biopsy is relatively safe, it is still associated with a risk of complications, patient discomfort and a high cost. In addition, liver biopsy examinations may lead to false negative results due to inadequate liver tissue sampling. Therefore, there is a need to develop a simple, reliable and non-invasive modality in order to assess the liver fibrosis stage [1].
Ultrasound (US) is a non-invasive, inexpensive and repeatable modality and has been used as the most important and valuable diagnostic tool for detecting hepatocellular carcinoma (HCC) during the follow-up of patients with viral hepatitis [2, 3]. US is also used for monitoring the response of HCC to treatment.
An ultrasound evaluation of the liver fibrosis stage of chronic liver disease has been performed by assessing various ultrasound factors such as the liver size, the bluntness of the liver edge, the coarseness of the liver parenchyma, nodularity of the liver surface, the size of the lymph nodes around the hepatic artery, the irregularity and narrowness of the inferior vena cava, portal vein velocity or spleen size [1, 4–8]. However, the conventional definition of the fibrosis stage of the liver based on evaluation of these ultrasound factors is imperfect and lacks accuracy and reliability. Furthermore, these findings also depend largely on the equipment used [8]. Indeed, a few reports have demonstrated no consistent correlation between the grey scale ultrasound findings and the histological findings, thus claiming that grey scale US is unreliable for grading and staging the degree of liver damage [9]. However, recent advances in US technology have improved the diagnostic accuracy for fibrosis in patients with chronic liver disease. Therefore, we carried out a study to evaluate the accuracy of the liver fibrosis stage by utilizing the techniques of advanced ultrasound performance in 103 patients with chronic liver disease and compared the results obtained with the histological findings.
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Patients and methods
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Patients
This study was prospectively designed. 103 consecutive patients, consisting of 60 males and 43 females with a diagnosis of chronic liver disease including liver cirrhosis at National Nagasaki Medical Centre between October 2001 and February 2003 were included. The mean age of the patients was 51 years old, with a range of from 38 years to 75 years. The inclusion criteria were as follows: (a) history of chronic liver disease, based on the detection of persistently high levels of aminotransferase; (b) an absence of clinical and/or biochemical signs of decompensated liver diseases (jaundice, ascites or encephalopathy); and (c) no previous histopathological diagnosis. Regarding the hepatitis virus, 22 patients were infected with HBV, 64 with HCV, 5 with both HBV and HCV and 12 with neither HBV nor HCV. Both ultrasound and histological examination obtained based on a liver biopsy were performed for all patients.
US system
The patients were studied ultrasonically using a real-time apparatus (HDI 5000 Sono CT, ATL, USA) with a 2–5 MHz convex array transducer C5–2 (low frequency probe) and a 5–12 MHz convex array transducer L12–5 (high frequency probe).
US findings and the scoring system (Table 1
)
The US examination was performed within an interval of no more than 15 days prior to the biopsy examination. The US examiners (TN, HW) were unaware of the clinical details of the patients, and the US findings were interpreted by two specialists (KY, HI) who had no knowledge of either the biochemical or biopsy results. The ultrasound examinations were recorded on static B-mode imaging. The US examiners were both certified by the Japan Society of Ultrasonics in Medicine. The US score was determined from the right and left lobes and the average score for each parameter was calculated as follows: (1) liver edge (Figure 1): score 0 for sharp; score 1 for mildly blunted; score 2 for blunted; (2) liver surface (Figure 2): score 0 for smooth; score 1 for mildly irregular; score 2 for irregular; score 3 for highly irregular; and (3) liver parenchymal texture (Figure 3) [5, 10]: score 0 for fine; score 1 for mildly coarse; score 2 for coarse; score 3 for highly coarse. A score of 0 was given when no abnormality was observed by a high frequency probe, score 1 was given when a mild abnormality was detected by a high frequency probe while it was undetected by the low frequency probe, a score of 2 was given when a moderate abnormality was detected by the low frequency probe, and a score of 3 was given when a severe abnormality was detected by the low frequency probe. A score of 2 was given for a blunted edge and a score 3 for severe irregular surface or a highly coarse texture when these characteristics were clearly confirmed by the low frequency probe. In cases in which three parameters such as the edge, surface and parenchymal texture could not be determined to be either mild or severe using a low frequency probe, then the high frequency probe was used to determine whether they were mild or severe. The high frequency probe was used to obtain a score 0 or 1 because the sensitivity obtained by the high frequency probe was superior to the one by the low frequency probe regarding mildly abnormal changes such as a score 0 or 1. Conversely, regarding such advanced changes as a score of 2 or 3, the low frequency probe was more useful because the probability obtained by the low frequency probe was superior to that by the high frequency probe. As a result, the fibrosis stage predicted from the accumulated scores of the liver edge, surface and parenchymal texture by US were considerably more reliable than the individual scores of these three parameters when they were compared with the histological findings.
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Figure 1. The ultrasound features of the liver edge; (a) a sharp edge with a high frequency probe, (b) a mildly blunted edge with a high frequency probe, and (c) a blunted edge with a low frequency probe.
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Figure 2. The ultrasound features of the liver surface; (a) a smooth surface with a high frequency probe, (b) a mildly irregular surface with a high frequency probe, (c) an irregular surface with a low frequency probe, and (d) a highly irregular surface with a low frequency probe.
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Figure 3. Scores for the ultrasound features of the liver parenchymal texture; (a) fine parenchymal texture with a high frequency probe, (b) a mildly coarse parenchymal texture with a high frequency probe, (c) a coarse parenchymal texture with a low frequency probe, and (d) a highly coarse parenchymal texture with a low frequency probe.
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Histological findings
Liver biopsy specimens were obtained from the anterior segment of the right lobe in each patient, using a 16-gauge Sonopsy-C1 biopsy needle (Hakko Co., Tokyo, Japan). All of the histological slides were reviewed by an experienced pathologist without any knowledge of the clinical details or the US findings. The New Inuyama scoring system for chronic hepatitis was proposed by the Japanese Liver Study Group in 1994 [11], which is similar to the classification of chronic hepatitis determined by the USA-European Liver Study Group [12]. The New Inuyama scoring system was used to assess the fibrosis stage as follows; score 0: no fibrosis, score 1: fibrous portal expansion, score 2: bridging fibrosis, score 3: bridging fibrosis with lobular degeneration, and score 4: cirrhosis.
Statistics
The Spearman's correlation test was used to assess any correlations between the liver fibrosis stage and the US scoring system. The sensitivity, specificity and positive predictive values of the US scoring system were calculated and compared with the results of the liver fibrosis stages.
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Results
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US scoring system and fibrosis stage
The relationship between the liver edge and fibrosis (Figure 4)
Of 11 patients with a sharp liver edge (edge score 0), 6 patients (55%) were found to have stage 0 fibrosis and 5 (45%) in stage 1 fibrosis. The liver edge score of 34 patients in an early fibrosis stage (stage 1) showed various results; 5 patients had a score of 0, 6 a score 0.5, 9 a score of 1, 5 a score of 1.5 and 9 a score of 2. On the other hand, the patients with stage 2, 3 and 4 fibrosis correlated well with the edge score and were categorized into a blunted edge (score 2); 26 of 26 patients with stage 2 fibrosis, 12 of 13 patients with stage 3 fibrosis, 22 of 22 patients with stage 4 fibrosis. The liver edge and the fibrosis score thus showed a statistically significant correlation (rs: 0.6668).
The relationship between the liver surface and fibrosis (Figure 5)
Eight patients with stage 0 fibrosis were all put into the smooth liver surface group (surface score 0), and 34 patients with the fibrosis stage 1 were all found to have a score of 1 or less. 26 patients with the fibrosis stage 2 had different results regarding the surface score, i.e. 3 patients had a surface score of 0, 7 a score of 0.5, 9 a score of 1, 4 a score of 1.5 and 3 a score of 2, respectively. 12 of 13 patients with stage 3 fibrosis were found to have a surface score of either 1.5 or 2. All 22 patients with the stage 4 fibrosis were found to have a surface score of 2 or more. The liver surface score and the fibrosis stage showed a statistically significant correlation (rs: 0.9007).
The relationship between liver parenchymal texture and fibrosis (Figure 6)
Eight patients with stage 0 fibrosis were all found to have a fine liver parenchymal texture (parenchymal score 0), and 29 of 34 patients with stage 1 fibrosis were found to have a score of 0. Of 26 patients with stage 2 fibrosis, 11 had a score of 0, 14 a score of 1 and 1 a score of 2. Five and 6 patients of the 13 patients with stage 3 fibrosis had a score of 1 and 2, respectively. All 22 patients with stage 4 fibrosis had a parenchymal score of 2 or more. The liver parenchymal score and the fibrosis stage showed a statistically significant correlation (rs: 0.8853).
Relationship between the fibrosis grade and the accumulated scores of the liver edge, surface and parenchymal texture (Figure 7)
The liver edge, surface and parenchymal texture scores were all determined and compared with the histological fibrosis score. Of eight patients with fibrosis stage 0, six patients were found to have a total score of 0 and while two had a total score of 1. 34 patients with stage 1 fibrosis had a total score 1.53 consisting of 2 patients with scores of 0, 11 and a score of 0.5–1, 17 had a score of 1.5–2.0, and 4 had a score of 2.5–3, respectively. 26 patients with stage 2 fibrosis shifted to the progressive fibrosis stage, such as 1 patient with a score of 1.5–2, 10 with a score of 2.5–3, 9 with a score of 3.5–4, and 6 with a score of 4.5–5, respectively. Similarly, 13 patients with stage 3 fibrosis shifted to a progressive fibrosis stage such as 1 patient with a score of 3.5–4, 5 with a score of 4.5–5, and 7 with a score of 5.5–6, respectively. Out of 22 patients with stage 4 fibrosis had a score of 6.5–7.0 and eleven had a score of 7–7.5, respectively. The fibrosis grade and the accumulated scores of these three parameters were more significantly correlated (positive predictive value, 0.9524) than the correlations of each score alone.
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Discussion
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Chronic liver diseases with viral infection manifest varying degrees of hepatic fibrosis ranging from no fibrosis to cirrhosis. Yoshida et al revealed that the annual incidence of hepatocellular carcinoma increased from 0.5% among patients with the stage F0 or F1 fibrosis to 7.9% among the patients with stage F4 fibrosis [13]. It has thus become increasingly apparent that the fibrosis stage is a key factor in defining the prognosis and management of chronic liver diseases with a viral infection.
The gold standard in hepatology for the diagnosis of the fibrosis stage has been a histological liver evaluation based on specimens taken either by a needle biopsy or at operation. Recently, non-invasive and reliable assessments for monitoring chronic liver disease using the platelet counts [14–16], aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratio [15, 16], and serum hyaluronan and type III procollagen amino-terminal peptide [17] have been developed. However, none of the currently available tests or modalities can completely replace a histological analysis. Previous studies have assessed several methods for evaluating the fibrosis stage of chronic liver disease using various US parameters. However, there have so far been few studies concerning the accuracy in detecting the signs of compensated cirrhosis by US [5, 18]. Gaiani et al [5] and Hung et al [19] proposed a complex US scoring system using indices of the liver surface, parenchymal echogenecity, the vessel pattern, spleen size etc. to determine the fibrosis stage. In addition, recent advances in ultrasound technology have now made it possible to obtain more precise information about the liver surface, edge and parenchymal texture [8]. Therefore, we conducted this study to clarify whether the US scoring system with a newly developed US equipment based on the conventional parameters of the liver edge, surface and parenchymal texture might obtain sufficiently accurate results in comparison with the histological findings for fibrosis obtained by a liver biopsy.
In this prospective study, among these parameters such as the liver edge, liver surface and liver parenchymal texture, the liver edge was not as specific for evaluating liver fibrosis as the liver surface and parenchymal texture in our study because a mildly blunted (score 1) or blunted edge (score 2) was frequently found in the early fibrosis stage (stage 1) (67.6%). On the other hand, the liver surface and liver parenchymal texture obtained by US showed a better correlation with the histological findings (correlation coefficient of 0.9007 in the liver surface, and 0.8853 in the parenchymal texture).
With conventional US, the liver surface has been most commonly utilized as a sole indicator for the diagnosis of cirrhosis [5, 20–22]. However, numerous papers have reported that the sole factor of the liver surface can not sufficiently distinguish cirrhosis from chronic hepatitis. Gaiani et al confirmed that the stage of cirrhosis may be underestimated when based on a single specimen and clarified that only two US variables, namely liver surface nodularity and the portal vein mean flow velocity, independently contributed to the diagnosis of cirrhosis [5]. In our study, all seven patients with a highly irregular surface were found to have cirrhosis (stage 4 fibrosis) histologically. On the other hand, 15 of 22 patients (68.2%) with cirrhosis were found to have an irregular surface (score 2–2.5), not a highly irregular surface (score 3). Indeed, the results of our study showed a significant correlation between the ultrasound liver surface and the histological fibrosis stage.
An irregular and nodular liver surface may be easily assessed in patients with decompensated liver cirrhosis, particularly in the case of ascites, and it has been observed in 88% of unselected patients with cirrhosis [20]. Gaiani et al reported the findings of a US scoring system, based on the liver, spleen and portal vein features, which identified cirrhosis in 82.2% of the cases [5]. In our study, both the right and the left liver lobes were evaluated for each factor, and the average score for each parameter was calculated. Both the low frequency and the high frequency probes were used to limit the subjective nature of the assessment of the US findings of various degrees. In this prospective study, US was performed with the simultaneous use of low frequency and high frequency probes to determine the sensitivity and probability according to the characteristics of ultrasound. Although our study was limited on account of the relatively small number of patients due to the strict inclusion criteria, 22 patients with an accumulated score of 6.5 or more were all found to have a fibrosis score of 4. Therefore, our scoring system for correctly predicting cirrhosis was found to be 100% sensitive. Furthermore, although the major drawback with US in comparison with the liver histology has been considered to be the failure to detect mild fibrosis or none at all, our scoring system thus provided relatively accurate information about liver fibrosis. When the accumulated US score of 3 was interpreted as mild fibrosis (a fibrosis score of 0 or 1), all 42 patients with stage 0 or 1 fibrosis were categorized into an accumulated US score of 3 or less (a probability of 100%) and 42 of 53 patients with a score of 3 or less were found to have stage 0 or 1 fibrosis (specificity of 79.2%). In addition, the score proposed in our study is easy to obtain and can be applied in every ultrasound laboratory by utilizing regular commercially available US equipment.
Evaluating the ultrasound pattern using either one or two parameters becomes much more complex at the stage of chronic liver disease than that of complete cirrhosis. Our scoring system based on three parameters such as the liver edge, surface and parenchymal texture was able to accurately predict the fibrosis stage (correlation coefficient of 0.9524), especially when distinguishing chronic hepatitis from compensated liver cirrhosis. When an exclusion of liver cirrhosis is requested, then US alone is therefore considered to provide sufficient information based on this scoring system. Furthermore, if a histological analysis can not determine the fibrosis stage correctly due to fragmentation or architectural distortion, then this ultrasound diagnostic modality of fibrosis could replace a histological diagnosis.
In conclusion, we demonstrated that our US scoring system is clinically useful for differentiating patients who have chronic liver disease with minimal or no fibrosis from those with mild to severe fibrosis. These parameters may also be useful for providing prognostic information and also for determining the optimal therapeutic options during the follow-up of patients with chronic liver disease, especially in patients with chronic hepatitis C or B, in order to predict the occurrence of HCC. In addition, further study is called for to determine whether or not the wider use of this scoring system could apply to other forms of hepatic fibrosis such as those suffering from long-term hepatotoxic disease, congenital diseases in children and non-viral infective forms of chronic liver disease in order to obtain an improved response to therapy.
Received for publication July 22, 2003.
Revision received August 31, 2004.
Accepted for publication October 5, 2004.
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Abstract
Introduction
