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Is ultrasound elastography of the liver ready to replace biopsy? A critical review of the current techniques

Accurate assessment of liver fibrosis in patients with chronic liver disease is necessary to determine prognosis, monitor disease progression and formulate treatment decisions. Currently, histological staging of liver biopsy is the most widely used reference standard for this purpose. Liver biopsy, however, has recognized risks, as well as sampling and observer error. These limitations have stimulated the search for new non-invasive approaches. Numerous methodologies, including serum markers, magnetic resonance elastography and ultrasound elastography, have evolved in the last decade to predict fibrosis in those with chronic liver disease. Ultrasound elastography methods assess liver fibrosis by determining liver stiffness and translate this into a quantifiable measurement for analysis. As these tests are non-invasive, without side-effect or discomfort, it is possible to conduct repeat examinations at much closer intervals than biopsy. The three most investigated ultrasound elastography methods are transient elastography, realtime elastography and acoustic radiation force impulse. Although significant strides have been made in the development of the technology, an unequivocal advocacy of elastography as a surrogate for biopsy is still not established. The aim of this review is to evaluate the advantages, limitations and clinical relevance of the three ultrasound-based modalities. Also, the review shall assess the current and possible future clinical application the modalities may serve both separate and in conjunction with liver biopsy.