WFUMB guidelines and recommendations for clinical use of ultrasound elastography - Part 3 - liver

2015 Ultrasound in Medicine and Biology 41, 5 (1161-1179)

TRANSIENT ELASTOGRAPHY
Recommendations
- The interpretation of TE results should always be in the hands of an expert clinician and should be made in light of the patient demographics, disease etiology and key laboratory findings, as well as according to the manufacturer’s recommendations, particularly the IQR/M ratio, which should be less than 30%.
- The main limitation to the use of TE in clinical practice is its limited applicability in obese patients. The use of the XL probe reduces the failure rate in obese patients but results in a high rate of unreliable results (approximately 25%). The clinical value of unreliable results remains a matter of debate.
- TE cannot be performed in patients with ascites.
- Several factors, including acute hepatitis, cholestasis, liver congestion, and food intake, increase the liver stiffness. Therefore, TE should be performed in fasting patients, and avoided or interpreted cautiously in patients with elevated transaminases (.5 x upper limit of normal), cholestasis, congestive cardiac failure, ongoing alcohol intake or alcoholic hepatitis.
-TE has been well validated in chronic viral hepatitis (C better than B) and can confidently be used as first line method for staging liver fibrosis. This strategy remains to be validated for other liver diseases.
- Combining TE with serum biomarkers of fibrosis increases the diagnostic accuracy for significant fibrosis in patients with chronic hepatitis C, a strategy that needs to be validated for other liver diseases, such as hepatitis B or NAFLD.
- TE offers better performance for detecting cirrhosis than significant fibrosis and is currently the standard among non-invasive methods.
- In patients with cirrhosis, liver stiffness has a prognostic value for the occurrence of portal hypertension. However, TE cannot replace upper GI endoscopy for the detection of esophageal varices.
- Current evidence suggests that TE could be used for monitoring the response to antiviral treatment and for predicting the prognosis of patients with chronic liver disease.

RECOMMENDATIONS
- Is elastography useful in the evaluation of diffuse liver disease? Liver elastography is useful for the evaluation of diffuse liver diseases. The level of evidence is high for TE, moderate for PSWSM, and still low for SWSI and SE. Some methods have been used for more than ten years while others have been introduced more recently, resulting in large variability in the number of published manuscripts on different techniques. The majority of studies have evaluated patients with viral chronic hepatitis and results obtained in this setting may not be applicable to other clinical situations as the critical cut-offs are strongly dependent on the etiology. Values with shear wave-based elastography and with strain techniques vary between manufacturers. Thus, the cutoffs are both system and etiology dependent. Elastography is capable of distinguishing significant fibrosis (F2 or greater) from non-significant (F0 - F1) fibrosis. However, more data are needed to confirm its use to distinguish between consecutive stages of early fibrosis. It is also important to note that each method may provide different values expressed in different units (meters per second, kilopascals) or indices. Several confounding factors have been identified, such as liver inflammation, liver congestion and biliary obstruction. Elastography results should be interpreted in the full clinical context of the patient, taking into account the method used to obtain the results. Elastography can be used for follow-up of patients with chronic liver diseases.
- To what extent can elastography reduce the use of liver biopsies? In some countries, where liver elastography is used in clinical practice, the number of liver biopsies has decreased significantly. When elastography results are consistent with other clinical findings, liver biopsy may be avoided.

Pubmed : 25800942