Diagnosis of early-stage chronic pancreatitis by secretin-enhanced magnetic resonance cholangiopancreatography

Abstract

A diagnostic means of detecting chronic pancreatitis at an early stage, when the disease is still reversible, needs to be developed. Magnetic resonance cholangiopancreatography (MRCP) has recently been evolving as an important tool for the evaluation of chronic pancreatitis. In patients with moderate chronic pancreatitis, the pancreatic parenchyma displays an abnormal enhancement pattern on T1-weighted sequences after gadolinium administration. The presence of a signal intensity ratio of <1.7 in the arterial phase and/or delayed peak enhancement after contrast administration has a sensitivity of 92% and a specificity of 75% for the demonstration of early chronic pancreatitis. The secretin-induced pancreatic T2 signal intensity changes are significantly reduced in patients with a mild exocrine pancreatic insufficiency as compared with healthy volunteers. MRCP visualizes fluid in the pancreatic and biliary ducts as high signal intensity on heavily T2-weighted sequences. However, visualization of normal or minimally dilated pancreatic ducts by MRCP is more challenging because of their small size. Secretin administration stimulates fluid and bicarbonate secretion by the exocrine pancreas; consequently, it improves the pancreatic duct and side-branch delineation and allows an evaluation of the exocrine pancreatic function. Side-branch ectasia, mild ductal dilatation with loss of the normal gentle taper, and mural irregularities are the pathognomonic MRCP features of early-stage chronic pancreatitis. Through measurement of the duodenal filling, secretin-MRCP allows quantitative assessment of the exocrine pancreatic function, even in patients with a mild exocrine insufficiency. The morphology of the pancreatic ducts, particularly in the early stages, does not always correlate with the functional status. MRCP permits visualization of the ductal changes and furnishes functional information on the pancreas; this combination may enhance its diagnostic accuracy so that MRCP can become a valuable diagnostic means in early-stage chronic pancreatitis.