Reply to Ustundag et al.

 

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We read with great interest the letter by Ustundag and Eloubeidi regarding our study on diagnostic performance of endoscopic ultrasound (EUS) in patients with primary sclerosing cholangitis (PSC), and hereby respond to the issues brought up by the authors.

First, not only nine patients had the opportunity to undergo magnetic resonance cholangiopancreatography (MRCP) examination and 14 and 17 patients directly underwent endoscopic retrograde cholangiography (ERC) or liver biopsy, respectively. As we precisely described in our study [1], in 2 of 14 patients who underwent ERC, liver biopsy was performed first and showed signs of PSC. Furthermore, in 6 of 17 patients, liver biopsy was performed after MRCP remained inconclusive, and in 9 out of 11 patients, liver biopsy was the correct first (and thus only necessary) diagnostic procedure.

Secondly, various aspects have to be taken into consideration when judging the diagnostic paths used for the patients included in our study. The diagnostic decisions were made by experienced gastroenterologists in our department independent of EUS results and with approval of each patient after detailed education of the advantages and risks of the different suitable procedures. Decisions were also based on the clinical experience of the physician with each method in terms of diagnostic value and complications. These decisions of course shifted towards an increasing number of MRCPs over the past few years [2]. In our study, diagnostic paths were chosen based on laboratory results, ultrasound abnormalities (e. g. steatosis or signs of moderate or severe fibrosis), patients’ individual history or autoimmune antibodies. Furthermore, MRCP was not technically feasible in all patients (e. g. due to obesity or severe claustrophobia).

When addressing the issue of comparing MRCP with EUS, it must be borne in mind that there are difficulties regarding the accuracy of MRCP to detect PSC in the extrahepatic biliary tree [3], and, as a result of the EUS technique, EUS is not capable of assessing intrahepatic disease manifestation. Thus, the study was not designed to compare MRCP with EUS, but to evaluate the diagnostic accuracy of EUS in patients with PSC compared with patients with different causes of cholestatic liver disease [1]. We do not believe that a comparative study of EUS and MRCP would be reasonable, considering the different capabilities of both methods when evaluating the extra- and intrahepatic biliary tract.

Another point addressed by the authors is the appearance of the common bile duct (CBD) in EUS. We agree with their description that the two-layered structure measured represents the outer hyperechoic layer (serosa) and the hypoechoic mucosa. It is true, that intraductal ultrasound can provide better imaging of the CBD and can help distinguish malignant from benign stenoses [4], though its technique is also more invasive and not as widely available as EUS. Reliability of CBD imaging was not a problem when using our EUS criteria on PSC as the authors proposed, though we agree that these criteria have to be confirmed in larger studies. In addition, to our knowledge, no prospective data comparing EUS of the CBD in bacterial cholangitis and PSC are available. Anyhow, with EUS, an underlying pathology other than PSC (e. g. choledocholithiasis) can be reliably detected [5]. Especially in autoimmune pancreatitis, with characteristic findings not only of the pancreas, but also of the CBD with a diffuse and uniform thickening [6], EUS is of great value; however, as already discussed in our article, we do acknowledge that intrahepatic disease manifestation is a diagnostic gap of EUS.

Finally, in our opinion based on personal experience, the sensitivity and specificity of diagnosing and staging PSC with MRCP from published studies cannot always be reached in clinical routine. Still, we concur with the authors that MRCP is a major diagnostic tool in patients with cholestatic liver disease, suspicious for PSC. However, in patients with inconclusive or technically impossible MRCP, we believe that EUS is capable of providing valuable information and can reduce the number of interventions that carry significant risks such as liver biopsy or ERC.

• References

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