**9. Role of EUS and ERCP in the diagnosis of chronic pancreatitis**

The diagnosis of chronic pancreatitis is based on altered pancreatic morphology and function. However, there is variation in the imaging findings using different modalities among patients with clinical features suggestive of chronic pancreatitis which sometimes delays diagnosis.

The American College of Gastroenterology (ACG) recommends cross-sectional imaging such as MRI or CT as first-line in the diagnosis of chronic pancreatitis in combination with careful history, physical examination, exposure risk, direct and/or indirect pancreatic function tests. These are preferred over ERCP and EUS due to the less invasiveness, objectivity, availability and cost differences. Endoscopic ultrasound can however be utilized if the findings from the cross-sectional imaging are in question. If EUS is inconclusive, secretin-enhanced magnetic resonance cholangiopancreatography (s-MRCP) or secretin- enhanced EUS are recommended [30]. A systematic review and meta-analysis on diagnostic performance of imaging modalities in chronic pancreatitis compared the sensitivity and specificity estimates of EUS, ERCP, MRI and CT, with no significant differences noted. Sensitivities for ERCP, EUS, MRI and CT reported were 82%; 95%CI: 76–87%), 81% (95%CI: 70–89%), 78% (95%CI: 69–85%), and 75% (95%CI: 66–83%), respectively and specificities, 94%; 95%CI: 87–98%), 90%; 95%CI: 82–95%), 96%; 95%CI: 90–98%) and 91%; 95% CI: 81–96%) respectively [31]. In the same study, abdominal ultrasonography was reported to have the lowest accuracy in diagnosing chronic pancreatitis. EUS can detect pancreatic parenchymal and ductal changes with high sensitivity and specificity producing high resolution ultrasonographic images due to the close proximity of the pancreas to the gastric and duodenal lumen.

A total of ten EUS criteria have been proposed by the International Working Group for Minimum Standard Terminology in Gastrointestinal Endoscopy for diagnosing chronic pancreatitis including five parenchymal criteria (hyperechoic foci, hyperechoic strands, parenchymal lobularity, cysts, calcifications) and five ductal criteria (pancreatic duct dilation, pancreatic duct irregularity, hyperechoic pancreatic duct walls, visible pancreatic side branches, intraductal calcifications) [32]. Diagnostic probability depends on the number of criteria observed, presence of two or less rules out chronic pancreatitis, presence of five or more criteria provides and definitive diagnosis, and presence of two to five criteria is indeterminate requiring pancreatic function tests. Some of the pancreatic changes seen during EUS have however been also associated with advanced age, smoking, obesity in the absence of chronic pancreatitis. EUS is operator dependant with poor inter-observer agreement which affects the reliability and standardization of EUS interpretation [33].

The Rosemont criteria was developed by a group of 32 experienced endosonographers in an attempt to harmonize and standardize the EUS based diagnosis of chronic pancreatitis. Ductal and parenchymal EUS findings are divided into major A, major


### **Table 1.**

*Rosemont criteria for endoscopic ultrasound diagnosis of chronic pancreatitis [34].*


### **Table 2.**

*Interpretation of the Rosemont criteria [34].*

B and minor criteria with different weight to different findings. Based on the number and character of positive EUS criteria, EUS evaluation is classified as "consistent with CP", "suggestive of CP", "indeterminate for CP", or "normal" [34]. However, the Rosemont criteria does not improve the inter-observer agreement compared to the standard EUS criteria [34] (**Tables 1** and **2**).

Diagnosis of early chronic pancreatitis presents a clinical challenge. EUS has been shown to detect some of the early features of chronic pancreatitis not detected by other imaging modalities [35]. ERCP remains a last-line diagnostic test and should be rarely used outside of therapeutic purposes.

Currently, histology is the gold standard for diagnosing early and late stages of chronic pancreatitis but not routinely done due to considerations of safety in obtaining samples from the pancreas. EUS is useful in obtaining pancreatic biopsies for histopathological diagnosis of chronic pancreatitis and other causative factors like pancreatic masses, autoimmune hepatitis. EUS-guided Fine Needle Aspiration (FNA) or Fine Needle Biospy (FNB) can be utilized to obtain biopsies for cytological and histological evaluation especially for cystic and mass lesions [36–39].
