3.5 Diagnostic Testing
3.5.1 Biochemistry
There are no specific laboratory tests for CP.In most cases，serum amylase and lipase are normal or only mildly elevated（Steer et al.1995）.Patients with CP may continue to have acute exacerbations and elevations in their amylase and lipase.
3.5.2 Radiology
Imaging studies play an important role in the diagnosis of CP but they are not sensitive enough to detect early or minimal changes in the pancreas.In the INSPPIRE cohort，pancreatic calcifications were present in only nine（12%）on initial imaging，while ductal dilatation（61%），irregularity（47%），and stricture（21%），and pancreatic atrophy（21%）were more common（Schwarzenberg et al.2015）.Calcifications were rare in the pediatric age group.
Ultrasonography.Ultrasonography（US）is the first imaging of choice as it has high likelihood to delineate pancreas anatomy in children without the risk of radiation exposure（Darge and Anupindi 2009）.Although US performs well in pediatric AP（Abu-El-Haija et al.2014），the diagnostic accuracy in CP has not been studied（Nydegger et al.2006）.US is helpful in assessing the pancreatic duct diameter in children with CP（normals are：≤1.5 mm in children 1-6 years；≤1.9 mm at ages 7-12 years；≤2.2 mm at ages 13-18 years）.Calcifications and intraductal stones can also be detected with US in CP（Darge and Anupindi 2009）.
Endoscopic US（EUS）.EUS is technically feasible in children as young as 5 years of age（Varadarajulu et al.2005），but the experience is limited only to few studies（Stevens 2013）.There are no pediatric-specific EUS criteria for CP.
Magnetic resonance cholangiopancreatography（MRCP）.Due to its non-invasive nature and lack of radiation，MRCP has become the diagnostic imaging test of choice in children with CP（Delaney et al.2008；Tipnis and Werlin 2007）.MRCP can reliably detect pancreas atrophy，ductal dilatations，small filling defects，strictures，irregularities of the main pancreatic duct，and irregularity of side branches（Hansen et al.2013）（Fig.11.8）.Unlike ERCP that images ducts under pressure，MRCP visualizes the ducts in their normal physiologic state（Darge and Anupindi 2009）.Therefore MRCP may not reveal the details of small ducts，which may be important in diagnosing early CP.Secretin may be more important in children than in adults as it increases the detectability of the normally smaller pancreatic ducts on MRCP（Manfredi et al.2002）.More studies are needed whether secretin-MRCP（s-MRCP）is superior to MRCP in children for the diagnosis of CP（Manfredi et al.2002；Trout et al.2013）.
EndoscopicRetrograde Cholangiopancreateography（ERCP）.ERCP should mainly be reserved for therapeutic interventions（pancreatic duct stenting，sphincterotomy，stone extraction）in children.Although relatively safe and widely available，ERCP carries an overall morbidity of～7%，which includes acute pancreatitis（4%），hemorrhage（1%），cholangitis（1%），perforation（0.5%），and death（0.1%）（Lee and Conwell 2012）.In pediatric CP，ERCP findings include main pancreatic duct dilatation，ductal stones，and changes in the main duct branches and small ducts（Fig.11.9）.The ERCP-based grading system of CP severity has been developed in adults（Cambridge classification），but it has not been validated in children（Axon et al.1984）.(https://www.daowen.com)
Fig.11.8 MRCP findings in chronic pancreatitis.Magnetic resonance imaging（MRI/MRCP）in in a 9-year-old male with CP showing diffuse parenchymal atrophy，duct dilatations in the head and neck of the pancreas with several dilated side branches elsewhere.There are several foci of low signal intensity consistent with extensive pancreatic calcifications，including intraductal stones.（Image is courtesy of Dr.Andrew Trout，Cincinnati Children's Hospital，Cincinnati，Ohio，USA）
Computerized tomography（CT）with contrast.CT can detect advanced changes in CP，including calcifications，pancreas atrophy，fat replacement，and ductal dilatation（Fig.11.10）.CT has poor sensitivity to identify ductal abnormalities and subtle parenchymal changes and the radiation exposure is not preferred in the pediatric age range（Kinney and Freeman 2008；Nydegger et al.2006）.
Fig.11.9 ERCP changes in chronic pancreatitis.（a）ERCP fluoroscopy image from a child with idiopathic CP showing intraductal stone（arrow）with dilated main pancreatic duct；（b）dilated main pancreatic duct with dilated main side branches in a child with CP.（Image is courtesy of Dr.Tom K.Lin，Cincinnati Children's Hospital，Cincinnati，Ohio，USA）
Fig.11.10 CT changes in chronic pancreatitis.Computed tomography with intravenous and oral contrast，in a 9-year-old male with CP showing findings consistent with chronic pancreatitis including diffuse parenchymal atrophy and calcifications.（Image is courtesy of Dr.Andrew Trout，Cincinnati Children's Hospital，Cincinnati，Ohio，USA）