A major new step in non‐invasive evaluation of portal hypertension: elastography

Portal hypertension (PHT) is a major consequence of chronic liver diseases. Its assessment quickly emerged as particularly useful in clinical practice for screening esophageal varices, assessing long-term prognosis and guiding therapeutic interventions. Firstly, early diagnosis of large esophageal varices is justified by the effectiveness of primary prophylaxis of variceal bleeding (1), whereas preprimary prophylaxis remains ineffective and may be deleterious in alcoholic patients (2). Secondly, it has strong prognostic value, as high PHT levels are closely related to the risk of complications (bleeding, ascites) (3) and mortality (4). Thirdly, quantitative assessment of the PHT level helps predict clinical response to prophylactic treatments, such as beta blockers (5) and, in the event of variceal bleeding, is able to define the critical condition requiring urgent transjugular porto-systemic shunt (6). However, varice screening and portal pressure measurement are not easy to perform in clinical practice. Upper gastro-intestinal endoscopy is a semi-invasive procedure that is not well accepted by some patients or often requires costly sedation. Portal pressure measurement is a useful tool, but its applicability is still debated, mainly because this invasive procedure is available in a limited number of tertiary centres; indications are listed in the Baveno V recommendations (1). Attempts to circumvent the limits of conventional diagnostic tools led to the evaluation of non-invasive tools, particularly in the context of varice screening. Radiological examinations (especially computed tomography and Doppler ultrasonography) may be useful, but experience of this tool is limited (7). One promising option is the oesophageal capsule (7). A few trials have been performedwith first generation capsules providing suboptimal results precluding a clinical application. Randomized trials with second generation oesophageal capsules are in progress. Finally, because the magnitude of liver fibrosis correlates with the PHT level, non-invasive fibrosis tests were logically evaluated for predicting large oesophageal varices. Unfortunately, several blood tests were not sufficiently accurate to replace endoscopy (7). Elastography is one of the more recent diagnostic tools, with growing popularity, that accurately detects significant liver fibrosis and is particularly powerful for diagnosing cirrhosis. Numerous studies have investigated the benefit of elastography for the detection of oesophageal varices. Although the majority of them have used transient elastography (TE) (Fibroscan, Echosens, Paris, France), there was a large variability in sensitivity, specificity and positive and negative predictive values. This variability could be explained by several factors, such as the size of the population studied, the prevalence of esophageal varices in the study population, the aetiology of cirrhosis and especially, the liver stiffness cut-offs used to define the presence of oesophageal varices. It was therefore entirely appropriate to conduct a meta-analysis on the issue. This has just been carried out by Shi et al. in the Journal (8). In this meta-analysis, only 18 of the 46 studies devoted to the subject were considered. The authors concluded that elastography is a good screening tool for oesophageal varices, with a sensitivity, specificity, positive predictive value and negative predictive value of 87%, 53%, 79% and 64% respectively. Although these results are encouraging, the data do not provide a full picture on careful examination. Firstly, from a methodological point of view, we note that the pooled analyses provided significantly heterogeneous results regardless of the study endpoint, and are therefore difficult to interpret. Unfortunately, the authors did not take the trouble to explain the sources of heterogeneity and thus did not solve this problem. The cut-offs of stiffness used in the studies may play a major role in the heterogeneity of the results and only a meta-analysis of individual data could provide reliable results regarding the diagnostic performance of TE for a given liver stiffness cut-off. Secondly, from a clinical point of view, we note that the performance of elastography was no better for the diagnosis of large oesophageal varices those requiring therapeutic prophylaxis than for the diagnosis of oesophageal varices considered altogether, including small varices. Therefore, the results of elastography given in this study by Shi et al. (8) cannot be used directly to prescribe primary prophylaxis of variceal bleeding. Once again, only a meta-analysis of individual data would be able to provide the more relevant liver stiffness cut-offs for clinical practice. Only cut-offs providing predictive values higher than 90% for the presence or absence of large oesophageal varices would be useful in clinical practice. Many studies have shown that TE is correlated with hepatic venous pressure gradient (HVPG) especially when HVPG is <10 mmHg. Therefore, it is not surprising that the meta-analysis published in that issue