Читать книгу Clinical Pancreatology for Practising Gastroenterologists and Surgeons - Группа авторов - Страница 92

Acute pancreatitis is an acute inflammatory process of the pancreas that is divided into two distinct subtypes, interstitial edematous pancreatitis and necrotizing pancreatitis. This is based on the 2012 Revised Atlanta Classification, an international model used to improve communication among practitioners and increase standardization in radiology reports [1].

Magnetic resonance imaging (MRI) is a reliable and reproducible tool for diagnosis, grading, and identification of complications of acute pancreatitis. Advancement in MRI technologies, such as the use of surface phase array coils and parallel imaging, new and fast sequences such as three‐dimensional gradient echo technique (GRE) Dixon fat suppression, three‐dimensional respiratory triggering [2], and compensation sequences, have significantly improved spatial resolution and decreased total scan time [3]. Dynamic multiphase imaging after gadolinium‐based intravenous contrast administration provides invaluable information about severity of inflammation and parenchymal necrosis.

MRI is a noninvasive modality that accurately shows both parenchymal and pancreatic duct abnormalities and, in combination with magnetic resonance cholangiopancreatography (MRCP), provides comprehensive evaluation for etiologies underlying acute pancreatitis and other pancreatic diseases. MRCP sequences provide high‐resolution imaging of the pancreatic and bile ducts. They can depict duct stones as small as 2 mm in size, as well as identify congenital anomalies that may cause recurrent acute pancreatitis such as pancreas divisum and annular pancreas [4].

MRI of the pancreas using intravenous synthetic secretin hormone provides invaluable information. Secretin stimulates exocrine pancreatic secretion of bicarbonate‐rich fluid from the acinar cells of the pancreas into the duodenum, which can be imaged using fluid‐sensitive T2‐weighted MRCP sequences. Secretin enhancement improves visualization of the main pancreatic duct and associated anomalies such as pancreas divisum, subtle ductal stricture, and exocrine function of the gland [5].

MRI has multiple advantages in the setting of acute pancreatitis when compared with the use of computed tomography (CT). MRI is more sensitive than CT in identifying pancreatitis, since mild or early acute disease [6] may not change the morphology of the pancreas but can show interstitial edema that is visible as increased T2‐weighted MRI signal around the gland. This, along with supporting clinical findings, may be sufficient to make the diagnosis of acute pancreatitis.

This ability of MRI to provide excellent soft‐tissue contrast is not dependent on the use of intravenous contrast. This is especially useful in patients with renal failure, who ordinarily do not receive intravenous contrast agents during MRI or CT. Noncontrast CT has a very limited role to play in the evaluation of acute pancreatitis, and while intravenous contrast is always preferred for the evaluation of necrosis and vascular complications, noncontrast MRI can still evaluate for pancreatic edema and surrounding fluid collections with good sensitivity. In addition, one of the most common causes of acute pancreatitis is underlying gallstones, which can be diagnosed with MRCP with similar accuracy as endoscopic retrograde cholangiopancreatography (ERCP). MRCP also visualizes the biliary and pancreatic ducts to assess for ductal obstruction, abnormal duct anatomy, and stricture.