Focal autoimmune pancreatitis: role of “modern” endoscopic ultrasound endoscopy?

We read with interest the review by Maillette de Buy Wenniger et al. [1] on the immunoglobulin-G4-associated disease of the pancreas and biliary tree. The authors illustrated in detail the multidisciplinary diagnostic approach of autoimmune pancreatitis (AIP), which combines histology, imaging, serology, other organ (nonpancreatic) involvement, and response to steroid therapy (Mayo HISORt criteria) [1] [2].

We would like to comment on the role of new endoscopic ultrasound (EUS) techniques in the diagnosis of focal AIP. Due to the absence of pathognomonic features on standard imaging studies, tissue sampling is generally necessary to firmly establish the diagnosis. However, is tissue sampling sufficient to both exclude malignancy and be specific enough for a diagnosis of AIP? EUS-guided fine-needle aspiration (FNA) has an accuracy of between 85 % and 95 % for cancer diagnosis, with still a significant rate of false-negative results, which indicates the need for repeat EUS – FNA [3] [4] [5]. However, negative cytology or histology obtained by EUS – FNA does not exclude AIP. In order to further investigate these subgroups of patients, the endoscopist possesses two promising imaging tools: real-time EUS elastography of the pancreas [6] [7] [8] [9] and/or contrast-enhanced EUS [10] [11] [12]. Of course, these modalities need state-of-the-art ultrasound systems, and new technology comes with a price tag.

Elastographic imaging of pancreatic tumors is usually homogeneous and largely dominated by blue (stiff) areas or strands, with normal elastographic patterns in the remaining parenchyma [6]. Conversely, patients with focal AIP present with a unique pattern of small spotted mainly blue color signals that are evenly spread [6]. In addition, when targeted masses are unclear on fundamental B-mode EUS imaging, elastography may be useful to find the targeted area [7].

Contrast-enhanced EUS using Doppler mode has also proved useful in the discrimination of pancreatic cancer from focal chronic pancreatitis [10]. Focal AIP presents a net-like hypervascularization pattern after contrast agent injection [11]. Conversely, color and power Doppler demonstrate a relatively hypovascular pattern in pancreatic adenocarcinoma compared with the remaining pancreas parenchyma, with a sensitivity and specificity comparable to cytopathology [11] [13].

We believe therefore that EUS elastography and contrast-enhanced EUS alone or in combination are promising tools in the diagnostic approach of focal AIP. Although, they may be considered as “toys” by some experts, it seems that in the near future their use might be integrated in the diagnostic algorithms of AIP.

• References

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• 2 Chari ST, Takahashi N, Levy MJ et al. A diagnostic strategy to distinguish autoimmune pancreatitis from pancreatic cancer. Clin Gastroenterol Hepatol 2009; 7: 1097-1103
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• 12 Săftoiu A, Iordache SA, Gheonea DI et al. Combined contrast-enhanced power Doppler and real-time sonoelastography performed during EUS, used in the differential diagnosis of focal pancreatic masses (with videos). Gastrointest Endosc 2010; 72: 739-747
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