Groove pancreatitis: CT, MRI & MRCP findings

Clinical History

A 51-year-old male patient presented with recurrent episodes of upper abdominal pain for the past year. The pain was chiefly localised to the epigastrium and also radiated to the back. Laboratory tests revealed mildly elevated serum amylase and lipase. Liver function tests were within normal limits.

Imaging Findings

US of the abdomen revealed GB sludge and dilated main pancreatic duct (MPD) raising the suspicion of chronic pancreatitis. CT visualized an ill-defined poorly enhancing soft tissue sandwiched between the pancreatic head and the duodenum. It displayed heterogeneous appearance with foci of calcification. Adjacent duodenal wall thickening was present. MPD was dilated. No overt calcification was seen in the pancreatic parenchyma. The peri-pancreatic fat planes, except in the pancreatico-duodenal groove, were preserved. MRI confirmed the presence of an ill-defined soft tissue in the pancreatico-duodenal groove which was closely abutting the head of pancreas. MPD was dilated and showed a subtle beaded appearance. Cystic areas were seen within the groove on T2-weighted imaging. MRCP revealed widening of the space between the duodenum and the distal common bile duct (CBD) and pancreatic ducts with presence of cystic lesions in the pancreatico-duodenal groove. Imaging findings were consistent with 'segmental' groove pancreatitis.

Discussion

"Groove pancreatitis" is an uncommon form of chronic pancreatitis which is localised within the "groove" between the head of pancreas, the duodenum and the common bile duct. It was first described in 1973 by Becker and Bauchspeichel, however, Stolte et al. coined this term in 1982. In 1991, Becker and Mischke classified it into 2 subtypes: pure and segmental form. In the 'pure' form only the pancreatico-duodenal groove is involved, with sparing of the pancreatic parenchyma and the main pancreatic ducts; while in its 'segmental' form the head of the pancreas is also involved.

The exact etiopathogenesis is contentious, although quite a few factors such as heterotopic pancreatic parenchyma in the duodenal wall, peptic ulcer disease, gastric resection, true duodenal-wall cysts, and disturbance of flow in MPD have been linked to this condition. A disturbance of the pancreatic outflow in the Santorini duct through the minor papilla has been attributed. Histopathological analysis of groove pancreatitis reveals scar tissue in the pancreatico-duodenal groove. This is frequently associated with scarring of the duodenal wall which can lead to recurrent vomiting.

At CT examination, groove pancreatitis is seen as a hypoattenuating poorly enhancing soft tissue mass in the pancreatico-duodenal groove. Duodenal wall is frequently involved and thickened. This may be accompanied with cysts in the duodenal wall and/or the groove. It is unclear whether groove pancreatitis and cystic dystrophy of the duodenum are distinct entities or part of the same spectrum. Hence, a broad category labeled 'paraduodenal pancreatitis' has been proposed to include groove pancreatitis, cystic dystrophy of the duodenal wall and paraduodenal wall cysts. The most characteristic finding on MRI is sheet-like mass corresponding to the fibrous scar in the groove. This exhibits hypointense signal relative to the pancreatic parenchyma on T1-weighted images with isointense/ hypointense/ or slightly hyperintense signal on T2-weighted images. Cystic lesions of the groove and/ or the duodenal wall are well displayed on T2-weighted images. Dynamic contrast study has been suggested to differentiate groove pancreatitis from groove pancreatic-carcinoma. On portal venous phase, patchy focal enhancement is seen in groove pancreatitis while a peripheral enhancement is more in favour of groove pancreatic-carcinoma. MRCP can show widening of the space between the duodenal lumen and the distal CBD and pancreatic ducts. A long segmental smooth distal CBD stenosis may be present as opposed to an irregular stricture with shouldering in groove carcinomas. Obstructive jaundice and elevated tumor-markers also suggest groove carcinoma.

Differential Diagnosis List

Final Diagnosis

Groove pancreatitis

URL:	https://www.eurorad.org/case/9404
DOI:	10.1594/EURORAD/CASE.9404
ISSN:	1563-4086