Laboratory Studies
If pancreatitis is suspected, amylase and lipase levels should be measured, as they may support a clinical diagnosis. However, these laboratory test findings alone are not reliable or cost effective as a screening tool, and the magnitude of enzyme elevation does not correlate with the severity of pancreatic injury. [12]
Elevated serum or urine amylase levels aid in the diagnosis of pancreatitis and peak 48 hours after onset. Serum amylase levels are typically elevated for as long as 4 days. Amylase levels have been found to be within the reference range in 10-15% of patients with pancreatitis. Amylase levels can be elevated in patients with other abdominal conditions, but typically, they are not as high as levels found in patients with pancreatitis.
Serum lipase is more specific than amylase for acute pancreatitis, and typically, lipase levels remain elevated 8-14 days longer than amylase levels. Serum lipase levels can also be elevated in patients with other diseases or conditions; therefore, all laboratory results should be evaluated in the context of the clinical presentation.
Other laboratory abnormalities found in patients with pancreatitis may include coagulopathies, leukocytosis, hyperglycemia, glucosuria, hypocalcemia, hyperbilirubinemia, and elevated gamma glutamyl transpeptidase.
Urinary levels of trypsin activator peptide (TAP) may help determine the severity of the pancreatitis.
Imaging Studies
Ultrasonography and CT scanning are the preferred imaging modalities used to diagnose and follow the course of pancreatitis and pancreatic pseudocysts. Ultrasonography is the primary screening tool for evaluation of the pediatric pancreas, due to the absence of ionizing radiation and ability to image without sedation. CT scanning may be better suited for evaluation of chronic pancreatitis and its complications, pancreatic trauma, and neoplastic conditions and is often used to further evaluate abnormalities found on ultrasonography.
Ultrasonography findings may include a focally or diffusely enlarged, hypoechoic, sonolucent, or edematous pancreas; dilated pancreatic ducts; a pancreatic mass; a fluid collection or peripancreatic fluid; an abscess; or a pseudocyst demonstrated as a well-defined, hypoechoic mass, which may be multilocular.
CT scan findings include an enlarged gland with ill-defined margins; peripancreatic fluid; areas of decreased or enhanced density; or pseudocysts with a well-defined wall or capsule and central area of low attenuation. CT scanning is a better modality for evaluating presence and extent of pancreatic necrosis and inflammation of peripancreatic fat. Of note, findings on imaging studies initially appear normal in 20% of children with acute pancreatitis.
MRI is another modality to diagnose pancreatitis and is used for the same indications as CT scanning.
Endoscopic retrograde cholangiopancreatography (ERCP) is essential for evaluation of pancreatic and biliary anomalies. ERCP can aid in the diagnosis of various ductal abnormalities or obstructions and may serve as a therapeutic intervention (ie, sphincterotomy, stent placement).
Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive alternative to ERCP but lacks therapeutic capabilities.
Roentgenography may demonstrate nonspecific findings ranging from a distended loop of small intestine (ie, sentinel loop), calcifications, radio-opaque gallstones, dilation of the transverse colon (ie, cutoff sign), ascites, peripancreatic extraluminal gas bubbles, ileus, left-sided basal pleural effusion, and blurring of the left psoas margin to pancreatic calcifications from chronic or recurrent pancreatitis.
Histologic Findings
Acute pancreatitis is characterized by enzymatic necrosis and inflammation of the pancreas. Focal areas of fat necrosis are interspersed with areas of interstitial hemorrhage secondary to destruction of blood vessels. In severe cases, large blue-black hemorrhagic foci are interspersed with yellow-white chalky areas of fat necrosis.
Chronic pancreatitis is characterized by irreversible destruction of the pancreatic parenchyma and subsequent replacement with fibrous tissue. Histologic features include intraglandular fibrosis, acinar cell destruction, lymphocytic infiltration, and pancreatic duct obstruction. The pancreatic ducts are dilated and obstructed with protein plugs in their lumens. Grossly, the gland is hard.
Pancreatic pseudocysts are localized collections of pancreatic secretions walled off by granulation tissue that lack a true epithelial lining. The stomach, duodenum, small bowel, colon, or omentum may abut or form part of the pseudocyst capsule.
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This CT scan of the abdomen in the region of the pancreas demonstrates a large well-marginated cystic structure that represents a pancreatic pseudocyst.
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This real-time ultrasonography of the abdomen, with attention to the right upper quadrant, revealed a loculated fluid collection in the hilum of the liver. This was compatible with a pancreatic pseudocyst. Differential diagnosis included a large choledochal cyst.
