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Normal Anatomy and Disease Processes of the Pancreatoduodenal Groove: Imaging Features

¹ All authors: Department of Radiology, Abdominal Imaging Section, Virginia Commonwealth University, Medical College of Virginia Hospitals and Physicians, 1250 E Marshall St., PO Box 980615, Richmond, VA 23298-0615.

Received July 9, 2003; accepted after revision April 26, 2004.

Address correspondence to J. Yu (jiyu{at}hsc.vcu.edu).

The pancreatoduodenal groove is a potential space bordered by the head of the pancreas, duodenum, and common bile duct [1–3] (Fig. 1). Diseases arising from or involving the pancreatoduodenal groove can be categorized into four types: diseases associated with the pancreas, duodenum, lymph nodes, and distal common bile duct. We present the key diagnostic findings of these diseases, along with features that can be used to distinguish among them, in this pictorial essay. Knowledge of the features of each disease may allow one to make a specific diagnosis, which assists in clinical management and helps to prevent unnecessary surgical intervention.

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1. —Schematic drawing of anatomy of pancreatoduodenal groove. Arrowheads indicate groove formed by junction of pancreatic head (P), duodenum (D), and bile duct (B). Arrows indicate small lymph nodes, normally present in groove.

Anatomy

The specific borders of the pancreatoduodenal groove are as follows: The medial border of the pancreatoduodenal groove is formed by the pancreatic head. The serosal surface of the descending duodenum is intimately related to the pancreatic head and forms the lateral border of the pancreatoduodenal groove (Figs. 2A and 2B). The posterior border of the groove is formed by the third portion of the duodenum or by the inferior vena cava. Because the distal common bile duct lies either in the parenchyma of the pancreatic head or adjacent to the posterior aspect of the pancreatic head, the distal common bile duct traverses the posterior aspect of the pancreatoduodenal groove. The anterior border of the pancreatoduodenal groove is formed by the first portion of the duodenum and at times by the gastric antrum. Normally, there are small lymph nodes in the groove that are not generally depicted on imaging.

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —Normal anatomy of pancreatoduodenal groove in healthy 46-year-old woman. P = pancreatic head, D = duodenum. Axial CT scan of abdomen shows potential space (arrows) between pancreatic head and duodenum.

View larger version (120K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —Normal anatomy of pancreatoduodenal groove in healthy 46-year-old woman. P = pancreatic head, D = duodenum. Axial T2-weighted image shows duodenum, pancreatic head, and groove (arrows).

Diseases Associated with the Pancreas

Groove Pancreatitis
Groove pancreatitis is a form of chronic segmental pancreatitis affecting the groove in the region of the pancreatic head, duodenum, and common bile duct [1–3]. There are two forms of groove pancreatitis: pure and segmental. The pure form of groove pancreatitis affects the groove only, and the segmental form involves the head of the pancreas, with scar tissue located in the groove [3]. The pathogenesis of groove pancreatitis remains unclear, although several factors such as peptic ulcers, gastric resection, true duodenal-wall cysts, and pancreatic heterotopia in the duodenal wall may be related to this condition [3]. On IV contrast–enhanced CT or MRI, soft-tissue-attenuation material with delayed enhancement is noted between the pancreatic head and the adjacent duodenum [1, 2] (Figs. 3A, 3B, 3C, and 3D). Irie et al. [1] described the MRI features of five patients with groove pancreatitis. They noted a sheetlike mass in the pancreatoduodenal groove that was hypointense relative to the pancreatic parenchyma on T1-weighted images and isointense or slightly hyperintense on T2-weighted images. Histologic analysis revealed that these imaging features correlated with fibrous scar in each of the five patients.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A. —Groove pancreatitis in 47-year-old man with history of pancreatitis. P = pancreatic head, D = duodenum. Axial T2-weighted image shows groove pancreatitis (arrows) that is slightly hyperintense relative to pancreatic head and contains focal areas of markedly increased signal intensity.

View larger version (131K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B. —Groove pancreatitis in 47-year-old man with history of pancreatitis. P = pancreatic head, D = duodenum. Axial T1-weighted image indicates lesion (arrows) with low signal intensity between pancreatic head and duodenum.

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3C. —Groove pancreatitis in 47-year-old man with history of pancreatitis. P = pancreatic head, D = duodenum. Dynamic axial MR image obtained during arterial phase after IV administration of gadolinium shows minimal enhancement of lesion (arrows) between pancreatic head and duodenum.

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3D. —Groove pancreatitis in 47-year-old man with history of pancreatitis. P = pancreatic head, D = duodenum. Delayed contrast-enhanced axial T1-weighted MR image obtained 5 min after injection of gadolinium shows partial enhancement of lesion (arrows) between duodenum and pancreatic head.

Cystic dystrophy of the duodenal wall, an entity that is most likely related to groove pancreatitis, is characterized by the presence of cystic lesions in the thickened wall of the second portion of the duodenum (Figs. 4A and 4B). The thickening of the duodenal wall appears as a solid layer between the duodenal lumen and the pancreas that exhibits delayed enhancement on contrast-enhanced CT [4]. The macro- and microscopic features of groove pancreatitis reported in the literature [1–3] are quite similar to those reported for cystic dystrophy of the duodenal wall [4].

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A. —Cystic dystrophy of duodenal wall in 58-year-old man with history of pancreatitis. Axial CT scan shows cystic lesion (solid arrows) in thickened duodenal wall with peripheral enhancement. Cystic lesion is lateral relative to pancreatic head and medial relative to duodenal lumen. Inflammation in anterior pararenal space (open arrow) is caused by pancreatitis. P = pancreatic head, D = duodenum.

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B. —Cystic dystrophy of duodenal wall in 58-year-old man with history of pancreatitis. Coronal MR cholangiopancreatographic image shows high-signal-intensity cystic lesion (solid arrows) in duodenal wall medial to gallbladder (G) and anterior and lateral to common bile duct. Open arrow indicates common hepatic duct. Diagnosis of cystic dystrophy of duodenal wall was confirmed surgically.

The differentiation of groove pancreatitis (especially the segmental form) from pancreatic carcinoma may be difficult, particularly in those cases of pancreatic carcinoma that have a significant fibrous component and therefore may display delayed enhancement similar to that seen with groove pancreatitis. On MR cholangiopancreatography, the intrapancreatic portion of the bile duct in patients with groove pancreatitis has a long, smooth, narrowed configuration, in contrast to the abrupt, circumscribed, irregular ductal stenosis or complete ductal obstruction seen in patients with pancreatic carcinoma.

Acute Pancreatitis
Acute pancreatitis with fluid collections and inflammation in the peripancreatic spaces, including in the pancreatoduodenal groove (Figs. 5A and 5B), is different from groove pancreatitis. Fluid collections and inflammation in the groove from acute pancreatitis exhibit rapid interval change on serial imaging studies and have high signal intensity on T2-weighted imaging.

View larger version (131K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A. —Fluid collection evolving into pseudocyst in pancreatoduodenal groove in 47-year-old man with acute pancreatitis. P = pancreatic head, D = duodenum. Axial CT scan reveals small amount of fluid (arrows) in groove between pancreatic head and duodenum.

View larger version (129K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B. —Fluid collection evolving into pseudocyst in pancreatoduodenal groove in 47-year-old man with acute pancreatitis. P = pancreatic head, D = duodenum. Axial CT scan obtained 6 weeks after A shows small pseudocyst formation (arrows) in groove between pancreatic head and duodenum.

Exophytic Pancreatic Ductal Adenocarcinoma
Ductal adenocarcinoma of the pancreatic head sometimes may present as an exophytic mass that appears to arise from the pancreatoduodenal groove (Figs. 6A, 6B, and 6C). Key features of exophytic pancreatic ductal adenocarcinoma on CT and MRI that help to narrow the differential diagnosis from other entities affecting the groove include a mass that is inseparable from the pancreatic head, obstruction of common bile and pancreatic ducts, and adjacent vascular encasement.

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A. —Exophytic pancreatic ductal adenocarcinoma in 45-year-old man. Axial CT scan shows exophytic mass (arrow) in pancreatoduodenal groove that is inseparable from pancreatic head and medial wall of duodenum. P = pancreatic head, D = duodenum.

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B. —Exophytic pancreatic ductal adenocarcinoma in 45-year-old man. Coronal MR cholangiopancreatographic image reveals obstruction of distal common bile duct (arrow) with dilatation of more proximal biliary duct (C) and gallbladder (G).

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6C. —Exophytic pancreatic ductal adenocarcinoma in 45-year-old man. Coronal MR cholangiopancreatographic image shows obstruction of pancreatic duct at pancreatic head (solid arrow). Extrahepatic hepatic bile duct (C), intrahepatic ducts (open arrows), and gallbladder (G) are dilated.

Neuroendocrine Tumor
The pancreatoduodenal groove is an important space within the gastrinoma triangle whose vertices are the cystic duct confluence, the junction of the pancreatic neck and body, and the junction of the second and third portions of the duodenum [1, 5]. Gastrinoma is the most common neuroendocrine tumor occurring at the groove. On dynamic contrast-enhanced CT or MRI, neuroendocrine tumors enhance to a greater degree than normal pancreatic parenchyma during the arterial and capillary phases (Figs. 7A and 7B). The features that distinguish neuroendocrine tumors and specifically gastrinomas from ductal adenocarcinomas include intense homogeneous early enhancement on CT or MRI, high signal intensity on T2-weighted MRI, location of the mass within the gastrinoma triangle and perhaps even within the pancreatoduodenal groove, and hypervascular liver metastases [5].

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7A. —Surgically proven pancreatoduodenal groove gastrinoma extending into ampulla of Vater and duodenum with large duodenal hematoma in 50-year-old man. P = pancreatic head, D = duodenum, G = gallbladder. Contrast-enhanced axial CT scan shows enhancing mass (arrows) in pancreatoduodenal groove lateral to pancreatic head and medial to duodenum.

View larger version (116K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7B. —Surgically proven pancreatoduodenal groove gastrinoma extending into ampulla of Vater and duodenum with large duodenal hematoma in 50-year-old man. P = pancreatic head, D = duodenum, G = gallbladder. Contrast-enhanced axial CT scan shows mass (solid arrows) associated with large duodenal hematoma (open arrow).

Diseases Associated with the Duodenum

Duodenal Diverticulum
Duodenal diverticula typically occur in the periampullary region, along the medial aspect of the second and third portions of the duodenum in the pancreatoduodenal groove [6]. A duodenal diverticulum may mimic other groove diseases such as tumor or a pancreatic pseudocyst or abscess [4]. Duodenal diverticula may also occasionally become impacted with debris, leading to duodenal diverticulitis, which presents as an inflammatory process in the groove. Identifying intradiverticular oral contrast material or a small amount of gas and recognizing the communication with the duodenum assists one in making the correct diagnosis (Figs. 8A and 8B).

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8A. —Duodenal diverticulum in 70-year-old woman who was being evaluated for possible pancreatic mass seen on prior chest CT study. Air–fluid level (arrows) is medial relative to second portion of duodenum (D), anterior relative to inferior vena cava, and lateral relative to pancreas (P) on axial CT scan.

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8B. —Duodenal diverticulum in 70-year-old woman who was being evaluated for possible pancreatic mass seen on prior chest CT study. Coronal MR cholangiopancreatographic scan shows diverticulum with low signal intensity (single solid arrows) consistent with air. Diverticulum exerts mass effect on distal common bile duct (open arrow). Double solid arrows indicate pancreatic duct.

Exophytic Duodenal Adenocarcinoma
Adenocarcinoma may occur in the periampullary region of the duodenum. This tumor tends to be polypoid [7] and may lie in the pancreatoduodenal groove (Figs. 9A and 9B). An exophytic duodenal mass, duodenal mucosal destruction at the upper gastrointestinal tract, and common bile duct and proximal bowel obstruction are the major imaging features that are associated with this entity.

View larger version (136K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9A. —Exophytic duodenal adenocarcinoma in 59-year-old woman. D = duodenum, P = pancreatic head. Contrast-enhancing mass (arrows) in pancreatoduodenal groove is medial relative to dilated duodenum and lateral relative to pancreatic head on axial CT scan. Duodenal dilatation is reflective of obstruction.

View larger version (126K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9B. —Exophytic duodenal adenocarcinoma in 59-year-old woman. D = duodenum, P = pancreatic head. Axial CT scan obtained at level inferior to A shows enhancing mass (arrows) between pancreatic head and duodenum. Surgery confirmed diagnosis of exophytic duodenal adenocarcinoma.

Diseases Associated with the Lymph Nodes

Lymph nodes are located in the pancreatoduodenal groove. Specifically, the lymphatics of liver and biliary tract drain along the hepatoduodenal ligament that inserts at or near the pancreatoduodenal groove. Pancreatoduodenal nodes also receive lymphatic drainage from adjacent structures such as the duodenum and pancreas. Therefore, diseases of the liver, biliary tract, duodenum, and pancreas may cause enlarged lymph nodes in the pancreatoduodenal groove; these diseases include metastasis (Fig. 10), lymphoma (Fig. 11), and infection (Fig. 12). At times, differentiating a solitary enlarged lymph node from a pancreatic tumor is difficult, although a tumor often intrinsically involves and obstructs the pancreatic and common bile ducts.

View larger version (169K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 10. —Metastatic lymphadenopathy in 62-year-old man with history of lung carcinoma. On axial CT scan, necrotic lymph node (solid arrows) is seen in pancreatoduodenal groove between duodenum (D) and pancreatic head (P). Liver metastasis (M) and necrotic peritoneal metastasis (open arrow) are noted.

View larger version (136K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11. —Non-Hodgkin's lymphoma in 41-year-old man. Axial CT scan reveals large mass (M) medial relative to duodenum (D) and lateral and posterior relative to pancreatic head (P), consistent with enlarged lymph node. Metallic biliary stent (arrow) is seen in common bile duct.

View larger version (156K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 12. —Mycobacterium avium-intracellulare (MAI) infection in 35-year-old man with AIDS. Axial CT scan shows several low-attenuation lymph nodes (arrows) in pancreatoduodenal groove medial relative to duodenum (D) and lateral and posterior relative to pancreatic head (P). Open biopsy confirmed diagnosis of MAI infection in lymph nodes. G = gallbladder.

Diseases Associated with the Distal Common Bile Duct

Cholangiocarcinoma
Distal common bile duct carcinoma may present as a mass arising from the pancreatoduodenal groove. The key features of distal cholangiocarcinoma are biliary ductal dilatation terminating abruptly at a point of ductal wall thickening or a polypoid mass. If the obstruction of the distal common bile duct is at the level of the ampulla of Vater, it may be impossible to be certain, even at histologic examination, if the tumor originates from the bile duct, pancreas, or duodenum [8] (Figs. 13A and 13B).

View larger version (131K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13A. —Villous adenocarcinoma in periampullary region in 55-year-old woman. Axial CT scan shows mass in region of distal common bile duct (arrows) between pancreas (P) and duodenum (D).

View larger version (108K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13B. —Villous adenocarcinoma in periampullary region in 55-year-old woman. MR cholangiopancreatographic image reveals mass (arrows) in distal common bile duct (C) and pancreatic duct (P) that is medial relative to duodenum (D). G = gallbladder.

Choledochal Cyst
Distal dilatation of the common bile duct (choledochal cyst) may mimic a fluid collection in the pancreatoduodenal groove. An abrupt change of caliber at the junction of the dilated segment and normal ducts is common. Confirmation of the tubular dilated portion of common bile duct communicating with the hepatic ducts assists one in establishing the diagnosis.

References

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4. Procacci C, Graziani R, Zamboni G, et al. Cystic dystrophy of the duodenal wall: radiologic findings. Radiology1997; 205:741 -747[Abstract/Free Full Text]
5. Stabile BE, Morrow DJ, Passaro E. The gastrinoma triangle: operative implication. Am J Surg1984; 147:25 -32[Medline]
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