Teaching Case

A 42-year-old man with history of chronic alcohol abuse was admitted with acute epigastric pain and vomiting. Laboratory tests revealed increased amylase, lipase, total bilirubin and direct bilirubin. Ultrasonography was performed followed by contrast-enhanced CT. The patient was treated medically, and an abdominal MR was performed a few months later.

Ultrasound revealed duodenal thickening with some cystic areas within the wall (Fig. 1).

CT (Fig. 2a, b) revealed an infiltrating soft-tissue lesion in pancreaticoduodenal groove, associated with thickening of the duodenal wall, with some cysts within it. The pancreatic head was heterogeneous, with some small cystic lesions. The pancreatic body and tail parenchyma was unremarkable. The pancreatic duct and common bile duct were dilated. These imaging findings suggested the diagnosis of paraduodenal pancreatitis. The patient was treated medically and was discharged a few days later. On the MRI (Fig. 3a-c) performed a few months later, the pancreatic parenchyma was unremarkable, except for a small simple cystic lesion on the pancreatic head. The pancreatic main duct and common bile duct were normal caliber. There was no thickening of the duodenal wall. Nevertheless, small cystic lesions were observed within the duodenal wall, suggesting cystic duodenal dystrophy.  Endoscopic ultrasound confirmed the diagnosis of chronic pancreatitis.

Paraduodenal pancreatitis is defined as an uncommon type of focal chronic pancreatitis affecting the groove between the head of the pancreas, the duodenum, and the common bile duct [1-3]. This is a unifying term for entities such as groove pancreatitis, paraduodenal wall cyst and cystic dystrophy of heterotopic pancreas. Histopathological analysis of all of these conditions revealed common findings of chronic inflammatory, cystic and fibrotic changes in the duodenal wall and heterotopic pancreatic acinar tissue near the minor papilla [4].

Patients affected by paraduodenal pancreatitis are usually young men with a history of alcohol abuse in the majority of cases [2,5]. The pathogenesis of this condition remains unclear, but disturbances of pancreatic outflow over the Duct of Santorini are frequently involved [2].

Paraduodenal pancreatitis can be subdivided into a pure form which affects exclusively the groove and a segmental form, which also extends to the pancreatic head with a clear predominance in the groove [1,2].

The clinical manifestations of this condition are similar to the usual form of chronic pancreatitis, in addition to duodenal and biliary obstruction [1]. Jaundice often fluctuates in opposition to the continuous increase jaundice found in patients with pancreatic carcinoma [1,2,6]. Vomiting tends to be more pronounced, comparing to chronic pancreatitis, due to marked duodenal stenosis. Blood tests frequently show an elevation of serum pancreatic enzymes [2]. Another important clue to differentiate paraduodenal pancreatitis from carcinoma is the normal appearance of the peripancreatic vessels that may be displaced, but they do not show signs of obstruction or encasement [6].

At CT evaluation, paraduodenal pancreatitis is seen as a hypoattenuating poorly enhancing mass in the groove between the head of the pancreas and the C-loop of the duodenum. This may be accompanied by thickening of the duodenal wall and paraduodenal cysts [2,5].

On endoscopic sonography, it also has a varied appearance, including a hypoechoic and heterogeneous mass along the second portion of the duodenum with periduodenal and intramural fluid collections [1,2].

The most typical finding on MRI is a sheet-like mass corresponding to the fibrous scar in the groove. This mass is hypointense to the pancreatic parenchyma on T1-weighted images and can be hypo-, iso-, or hyperintense relatively to the pancreas on T2-weighted images. Other MR imaging appearances include inflammatory changes, groove cyst lesions, duodenal wall thickening, and duodenal stenosis [1,3].

Teaching point:

The focal thickening and cystic changes of the second portion of the duodenum, in a patient with pancreatitis, suggests the diagnosis of paraduodenal pancreatitis.