TO THE EDITOR
The recent paper by Wu et al entitled “Application of contrast-enhanced intraoperative ultrasonography in the decision-making about hepatocellular carcinoma operation” published in the January issue of World Journal of Gastroenterology reports some experiences of the authors in contrast-enhanced intraoperative ultrasound (CEIOUS) for hepatocellular carcinoma (HCC). This paper raises a couple of questions that, we believe, need to be asked about.
First and foremost, the authors did not mention any of the previously performed and published studies on the same topic on the application of CEIOUS for HCC[2-7]. Such studies not only represent the first pioneer investigations on CEIOUS, but up to now they are the cornerstones of this new intraoperative imaging modality, which needs to be confirmed or confuted by further studies performed by other groups. In this sense, Wu et al have lost this opportunity.
Second, it is unclear to the readers how the authors defined a lesion as malignant based on the CEIOUS findings. This is a pivotal point. Yet, CEIOUS for HCC requires a kind of classification to interpret its findings in order to make the correct diagnosis. In particular in case of cirrhotic liver, where the finding of multiple subcentimetric nodules is common, the typical arterial phase might not be very clear because some of those nodules are high-grade dysplastic nodules or early HCC with no anticipated standard contrast enhancement. Indeed, we proposed a classification that, we believe, could help in this sense, even if it probably requires some refinements.
Third, the reported value of specificity for CEIOUS is very high compared with that for intraoperative ultrasound (IOUS) and contrast-enhanced magnetic resonance imaging (CEMRI). The impression is that the authors calculated the specificity by adding the value of CEMRI and IOUS. When CEIOUS was performed on the same population of patients who had CEMRI and IOUS, its results in terms of sensitivity and specificity might be biased by the previous radiological findings. Only a true blind performance of different diagnostic methods might allow a true comparison in terms of diagnostic accuracy.
Finally, we thank that Wu et al, because our group, developed and supported the study of CEIOUS performed many years ago, both for HCC[2,4-6] and for colorectal liver metastases. Thus, any new study on the same topic further sustains its use.