Reply to Ustundag

We would like to thank the authors for their instructive comments.

According to our experience and follow-up studies (not published to date), and with regard to published articles, it is our feeling that focal and diffuse autoimmune pancreatitis (AIP) are stage-dependent and both stages could be seen as a continuum with overlap. In our study, therefore, patients with focal as well as those with diffuse AIP were included. It could be shown in patients with focal AIP that the elastographic pattern of the remaining pancreatic tissue is homogeneously stiff (hard), which can be used as a diagnostic sign [1]. In addition, we could show that the vascularization and perfusion pattern of the inflammatory tissue really does not matter in the earlier stages. In the end-stage disease, only fibrotic and sclerotic tissue is present but such patients were not included in our study. A prospective multicenter study investigating the stage-dependent diagnosis of AIP would provide useful information in this regard.

The authors of the letter are referring to a study by Figueiredo et al. [2], which included an unexplained difference in vascularization behavior in patients with AIP. Unfortunately, the study has only been published in abstract form to date. However, as far as we understand, the study refers to contrast-enhanced endosonography (CE–EUS) for the discrimination between benign and malignant pancreatic lesions and not for patients with AIP, which in our view is an important difference. We think that the contrast-enhancing behavior of AIP is not necessarily equal to that shown in chronic pancreatitis. Whereas it is well known that focal lesions from patients with chronic pancreatitis can be hypovascularized in the late stages (still showing arterial and venous vessels in pulsed wave Doppler measurements) [3], it is, in our experience, very rare in patients with AIP and is only seen in diffuse infiltrating end-stage diseases. We do not think that the study of Figueiredo really contradicts our work.

Regarding the need for histological or cytological proof of AIP, the comment by Ustundag et al. remains controversial: we would like to follow their suggestion, however it seems to be a risky approach. We know that nearly 11 % of pancreatic cancer lesions appear isodense compared with the surrounding tissue on computed tomography (CT) [4]; in our experience with CE–EUS in an unselected group of patients (including patients with chronic pancreatitis), the appearance of isodense lesions was up to 30 % [5]. Because lesions of suspected AIP should be primarily resectable, we do not recommend basing the decision of whether or not to resect the lesion on CT or EUS scans alone. In our case study, we attempted to assess whether or not the less invasive cytology investigation could compare with the more invasive histology investigation and were able to show positive results. However, whether our approach to substitute histology with cytology (in five patients) can be generally recommended should be the topic of further studies.

Regarding the technique and the investigation costs as well as the learning curve the comment of the authors have to be taken into account. However, comparing CT and particularly magnetic resonance imaging costs with the mentioned costs of the ultrasound contrast agents there is no doubt that contrast-enhanced ultrasound is much cheaper. What we could prove is that with the help of the right technique and a little more money in the hands of an experienced investigator in EUS, it is possible to improve the technique of EUS further. We believe that these cases can be used as the starting point for more technical developments and a broader usage of the interesting technique of CE–EUS (and sonoelastography).

References

• 1 Hirche T O, Ignee A, Barreiros A P et al. Indications and limitations of endoscopic ultrasound elastography for evaluation of focal pancreatic lesions.  Endoscopy. 2008;  40 910-917
• 2 Figueiredo F A, Giovannini M, Bories E et al. Endoscopic ultrasonography (EUS) strain ratio (SR-EUS) vs. contrast-enhanced EUS (CE-EUS) for the diagnosis of focal pancreatic lesions.  Gastrointest Endosc. 2009;  69 129
• 3 Hocke M, Schmidt C, Zimmer B et al. Contrast enhanced endosonography for improving differential diagnosis between chronic pancreatitis and pancreatic cancer.  Dtsch Med Wochenschr. 2008;  133 1888-1892
• 4 Prokesch R W, Chow L C, Beaulieu C F et al. Isoattenuating pancreatic adenocarcinoma at multi-detector row CT: secondary signs.  Radiology. 2002;  224 764-768
• 5 Hocke M. Klinische Bedeutung der kontrastverstärkten Endosonographie. [thesis]. Jena, Germany: Jena University; 2008