6.1 EUS Criteria
6.1.1 Traditional EUS Criteria
Traditional EUS criteria contain nine features，including parenchyma and ductal features（Table 7.6），and the surgical specimens showed that these criteria were related to the histological changes.Eleven diagnostic criteria introduced two additional criteria: pancreas enlargement and pancreatic duct stenosis（Gardner and Levy 2010；Raimondo and Wallace 2004；Bhutani et al.2009）.
The sensitivity and specificity of EUS in the diagnosis of CP were determined by the threshold.Low threshold result in higher sensitivity，which could be used to ruled out CP，but with poor specificity and high risk of over-diagnosis.In converse，high threshold can be used for diagnosis of CP.However，Endoscopic physician found the value of each EUS criteria is unequal in clinical practice（Catalano et al.1998，2009；Rajan et al.2005）.Rajan et al.study found the frequency of EUS abnormalities in patients without clinical evidence of CP increases with age，particularly after 60 years of age（Rajan et al.2005）.Their study showed in 120 patients with no history or symptoms of pancreaticobiliary diseases，28%of the patients had at least one parenchymal and/or ductualabnormality，which with a trend of increasing abnormality with age.Hyperechoic stranding was the most common finding in all age groups.And no patient had more than three abnormal EUS features.Therefore they thought the threshold number of EUS criteria for the diagnosis of CP is variable and ductal or parenchymal calculi，ductal narrowing，ductal dilatation，or more than three abnormalities appear to be more specific features for the EUS diagnosis of CP at any age.
Table 7.6 Nine EUS criteria for CP diagnosis and correlation histologic change
Table 7.7 Consensus-based parenchymal and ductal features of CP according to the new Rosemont classification（Catalano et al.2009）
aLocated in head，body or tail
bLocated in dorsal of head，body or tail；only located in body or tail
6.1.2 Rosemont Classification
It is precisely because of the predictive value of each EUS criteria weight EUS is inconsistent，most scholars believe that these criteria need to be optimized utilization.Therefore，in Apr，2007，a new classification criterion was made in an international consensus meeting which was convened in Rosemont.This system gives a strictly level for each criterion，including Major and minor criterion（Tables 7.7 and 7.8，Figs.7.16，7.17，and 7.18）（Catalano et al.2009）.
Table 7.8 Rosemont consensus for EUS diagnosis of CP（Catalano et al.2009）
Fig.7.16 Multiple strong echo foci in the parenchyma of the pancreas with acoustic shadows
Fig.7.17 Strong echo with acoustic shadow in main pancreatic duct（stone）
Fig.7.18 Pancreatic duct distortion and dilation
Sincethis classification system gives a strictly criteria for EUS based CP diagnostic，it plays an important role in CP diagnosis，especially in early stage（Catalano et al.2009）.But，its significance in diagnosis，treatment，and research of CP is need to be further verified and the criteria should be mortified and improved along with the progress of EUS technology and the deep understanding of the EUS features of various types of CP（Stevens and Parsi 2010；Park and Van Dam 2009）.In addition，due to the lack of strict histological comparison，the advantage of EUS in the early stage CP diagnosis has not been fully demonstrated，and factors such as age，body weight，smoking and other factors affect that the EUS based diagnosis still need further study（Gardner and Levy 2010；Stevens 2011）.(https://www.daowen.com)
6.1.3 EUS-Guided Fine Need Aspiration/Biopsy（EUS-FNA/B）
So far，few studies described the value of EUSFNA for CP diagnosis，due to the possible and severe complications related to the procedure and the lack of a generally agreed histologic definition of CP.Hollerbach et al.（2001）showed compared with EUS，EUS-FNA improves the negative predictive value，but it does not improve the specificity of EUS.Another study showed that in 14 patients with alcohol related CP who underwent EUS guided pancreatic fine needle biopsy（EUS-FNB），adequate tissue samples for histological evaluation were obtained in all cases and infiltration of inflammatory cells was observed in all tissue specimens（Iglesias-Garcia et al.2006）.Biopsies including pancreatic acini were those obtained from patients with mild to moderate EUS changes of CP（up to five EUS criteria）.But，biopsy samples from more severe cases（8-10 EUS criteria）were those showing only ductal epithelium with fibrotic components.Therefore although EUS-FNA may be an alternative choice for CP diagnosis and staging，its efficiency and safety for CP diagnosis are remain unclear.
6.1.4 EUS Guided Tru-Cut Biopsy（EUS-TCB）
EUS-TCB is superior to EUS-FNA in obtaining no-surgical modality specimen.A study evaluate the utility and the safety profile of EUS-TCB for the histologic diagnosis of suspected non-focal CP（DeWitt et al.2005）.In this study，16 patients with suspected CP（＞or=3 EUS criteria）underwent transgastric EUS-TCB of the pancreas.EUS-TCB results were as follows:one case of probable CP，two cases of normal pancreas，six cases of non-diagnostic CP，and one case of device malfunction.Complications occurred in two patients.Therefore，the author thought because of potential complications and limited diagnostic yield，this technique is not currently recommended for evaluation of these patients.
6.1.5 EUS and Histologic Correlation
At present，the correlation of EUS features of CP and histologic changes remain undetermined due to the limitation of specimen obtain and noconsensus of histologic diagnosis criteria（Gardner and Levy 2010；Levy and Wiersema 2005）.Varadarajulu et al.（2007）found that parenchymal feature of EUS were foci，stranding，and lobulations and ductal feature were dilated or irregular main pancreatic duct，side branches，and hyperechoic duct margins.Four or more EUS criteria provided the best sensitivity，specificity，and accuracy.But in Chong et al.（2007）reported that three or more EUS criteria was thought to provide the best balance of sensitivity and specificity for predicting abnormal histology.In addition，in a recent study（LeBlanc et al.2014），main pancreatic duct（MPD）dilation and irregularity were found to associated with moderate and severe fibrosis.Lobularity with honeycombing，hyperechoic foci with shadowing，hyperechoic foci without shadowing，MPD dilation，MPD irregularity，and dilated side branches were associated with severe CP.Therefore the importance of pancreatic ductal changes should not be minimized in the evaluation of CP.