Efficacy of Ultrasonography as a tool for detection of Fatty Liver S. P. Singh*, S. Nayak**, M. Swain***, O. P. Agrawalª, C. Meherª, M. V. K. Rao°, Niranjan Rout‡, R. N. Mallik¶
Departments of *Gastroenterology, ***Biochemistry and °Radiology, S.C.B. Me dical College, Cuttack 753007, India Department of **Gastroenterology and ªRadiodiagnosis, Beam Diagnostics Centre, Cuttack 753001, India. ¶Department of Pathology, V.S.S. Medical College, Burla, India. ‡Department of Oncopathology, Acharya Harihar Regional Cancer Centre, Cuttack 753007, India.
Address for Correspondence: Shivaram Prasad Singh, Associate Professor and Head, Department of Gastroenterology, S.C.B. Medical College, Cuttack 753007, INDIA. Email:
[email protected]
ABSTRACT Background: Fatty liver is a common clinical condition which is fast assuming importance as a possible precursor of more serious liver disorders including cirrhosis of liver and hepatocellular carcinoma. Aim: The present study was performed to evaluate the efficacy of ultrasonography for diagnosis of fatty liver. Methods: The ultrasonographic study data and histological data of all patients undergoing liver biopsy in the Gastroenterology Department of S.C.B.Medical College, Cuttack was analysed to evaluate the efficacy of ultrasonography in detecting fatty liver disease. Results: The subjects included 31 consecutive persons who underwent liver biopsy for evaluation of either fatty liver or raised transaminases. Fatty liver was diagnosed by ultrasonography in 25 of the 31 patients who underwent liver biopsy. All 25 patients with sonographic fatty liver had fatty liver on histology, while histology did not reveal fatty infiltration in any of the 6 patients in whom sonology did not reveal fatty liver. Thus the sensitivity and specificity of sonology for detecting fatty liver was found to be 100%. Conclusions: Ultrasonology is highly sensitive and specific for diagnosis of fatty liver. Hence ultrasonology which is noninvasive and safe can be used to study the prevalence of fatty liver in the asymptomatic general population. Key words: Hepatic steatosis, fatty liver, ultrasonography 1
INTRODUCTION Fatty liver is a common clinical condition where there is excessive accumulation of fat within the hepatocytes.1 Two main patterns of histology are seen: microvesicular and macrovesicular. Microvesicular steatosis which presents acutely is associated with mitochondrial dysfunction and has a uniformly grave prognosis. Macrovesicular steatosis is associated with chronic diseases. Fatty liver (macrovesicular steatosis) in the absence of consumption of alcohol in quantities known to produce liver disease is termed Nonalcoholic fatty liver disease (NAFLD). It is believed to consist of a spectrum of illness, which progresses from hepatic steatosis to Nonalcoholic steatohepatitis (NASH) and cirrhosis. It is postulated that fatty liver may be a cause of cryptogenic cirrhosis 2 and may even lead to hepatocellular carcinoma. 3 All this seems to suggest that fatty liver is not as benign as considered previously. Hence there is an increasing interest in this disorder. Although there are a few reports on NASH from India, 4-6 there is no data in published English literature on the prevalence of NAFLD in India. Hence there is a need to assess the prevalence of NAFLD in our country in order to assess the magnitude of the problem. Although histopathology is the gold standard to diagnose fatty liver, 7 it is not feasible to use an invasive procedure like liver biopsy for assessing fatty liver prevalen ce in the general population due to the possible complications associated with liver biopsy. Ultrasonography is believed to be a reasonably efficient tool for diagnosis of fatty liver. 810 This can be easily used to study the prevalence of fatty liver in t he general population if it is found to be reasonably sensitive and specific in diagnosing fatty liver. Therefore we decided to evaluate the efficacy of ultrasonography for diagnosis of fatty liver in our setting. MATERIALS AND METHODS The records of all the patients who underwent liver biopsy in the Department of Gastroenterology, S.C.B. Medical College, Cuttack during the period June 2002 to December 2002 were reviewed retrospectively particularly with respect to the histological diagnosis and ultrasonographic diagnosis with special reference to presence or absence of fatty appearance of the liver. Grey scale real -time ultrasonography was performed in these patients using a Toshiba Ultrasound Scanner (Model CAPASEE II) employing a 3.5mHz 40R convex probe. Fatty liver was diagnosed when the liver appeared bright and hyperechoic with poor visualisation of the deeper aspects of the liver due to strong attenuation of the ultrasound beam. 11 Liver biopsy was performed using Menghini’s liver biopsy needle employing the standard 1-second technique. Formalin fixed and paraffin embedded biopsy specimens were stained with hematoxylin and eosin for morphological evaluation, and with Reticulin stain and Masson’s trichrome stain for assessment of fibrosis. The diagnosis of NASH was based on ultrasonologic demonstration of fatty liver, the presence of histological features of steatohepatitis (macrovesicular steatosis), lobular and/or portal inflammation, with or without Mallory’s hyaline, fibrosis or cirrhosis, and exclusion of other causes of chronic liver disease in the absence of history of alcohol abuse. The data was then analysed to evaluate the sensitivity and specificity of ultrasonography in diagnosing fatty liver.
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RESULTS The study population consisted of 31 patients in whom liver biopsy was performed. Of these 31 patients, fatty liver was diagnosed by ultrasonography in 25 patients. In the remaining 6 patients, fatty liver was not appreciated by ultrasonography. In 3 of these six patients sonography had detected mild hepatosplenomegaly, hepatomegaly alone was found in one, splenomegaly alone was diagnosed in another and the remaining patient had no abnormal finding on sonography. Of the 25 patients in whom sonography detected fatty liver, histopathology revealed hepatic steatosis alone in 6 (24%) patients; histology of liver tissue obtained from the remaining 19 (76%) patients revealed features of nonalcoholic steatohepatitis (NASH). Histopathologic study of liver biopsy specimen in those patients who did not have fatty liver on sonography revealed chronic hepatitis in 3 patients, autoimmune hepatitis in one patient, amyloidosis in one and normal study in one. Thus in our study, both the sensitivity as well as specificity of ultrasonography for the detection of fatty liver was found to be 100%.
DISCUSSION Although histology is the gold standard for the diagnosis of fatty liver disease or nonalcoholic steatohepatitis,7 this is not appropriate for a population based study to detect the prevalence of fatty liver. Ultrasonography is a simple, safe and noninvasive procedure without any discomfort to the patients, and hence could be suitable for detecting and studying the prevalence of fatty liver provided it has reasonable sensitivity and specificity in diagnosing fatty liver. It has been used in the past to study the prevalence of fatty liver too.12,13 In our present study, ultrasonography was 100% sensitive and specific for diagnosis of fatty liver. Foster et al studied the accuracy of ultrasound in the detec tion of fatty liver and concluded that the sensitivity of ultrasound for detecting fatty liver was 90%.8 In a subsequent study by Saverymuttu et al, the sensitivity and specificity of sonography for detecting fatty liver was found to be 94% and 84% respect ively. 9 Another study by Graif et al that assessed the utility of ultrasound imaging to detect fatty liver in asymptomatic patients with elevated aminotransferases showed that this test had a sensitivity of 82% and a specificity of 66%; however for uncomplicated hepatic steatosis, the sensitivity of sonography was found to be 100% and specificity 60%. 10 Inspite of the small numbers, the results of our study clearly demonstrate that ultrasonography is highly efficacious in detecting fatty liver. The higher sensitivity and specificity of sonography in identifying fatty liver in our study could be due to the fact that sonography was performed by two very experienced and dedicated abdominal ultrasonologists, and it is a well known that ultrasonography is a high ly operator dependent procedure. Hence in our setting, ultrasonography can be used to study the prevalence of fatty liver in the general population. However, this procedure cannot substitute liver biopsy since it can’t reliably distinguish steatosis from s teatohepatitis or cirrhosis, and liver biopsy remains the most reliable test for diagnosing and staging the disease.7
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