Types of diseases in the pancreaticoduodenal sulcus area and imaging findings

Pancreaticoduodenal groove (PDG) is a small space between the head of the pancreas and the duodenum, allowing for multi-organ interactions and some physiological processes
.
Together, muscle, nerve and hormone enzymes help digest and absorb key nutrients
.
Due to the combined action of many organs and cells, various benign and malignant lesions can occur in or near this gap
.
Management of lesions in this area is also complex and includes exploration, endoscopic resection, or challenging surgery (such as Whipple).

Radiologists play an important role
in evaluating PDG lesions.
CT is usually the first-line test and MRI provides complementary information
.
Although the imaging findings of lesions involving PDG often overlap, understanding their characteristic and pathologic features, and based on the presence of suspected organ origin and other associated findings, can often classify the disease
.

The pancreas, common bile duct (CBD), and duodenum have intricate relationships
with the surrounding connective tissue, autonomic nerves, blood vessels, and lymph nodes.
The pancreaticoduodenal sulcus (PDG) is a thin anatomical space located anteriorly above the pararenal space, medial to the head of the pancreas, above the duodenal bulb, on the outside is the descending duodenum, below is the horizontal segment of the duodenum, and posterior is the inferior vena cava (IVC) (figure).

Anatomy of the pancreaticoduodenal region
.

AD/mP = parapancreatic duct and small papilla, Ao = aorta, AV/MP = Vater ampulla and large papple, CT = abdominal trunk, D = duodenum, G = PDG (purple), GDA = gastroduodenal artery, P = pancreas, PD = pancreatic duct, PDA = pancreaticoduodenal artery, PV = portal vein, SMA = superior mesenteric artery, SMV = superior mesenteric vein, SMV = superior mesenteric vein, SV = splenic vein
.
Histopathological features
of the pancreaticoduodenal region.

Vater ampulla (A), gastroduodenal artery (GDA), pancreaticoduodenal artery (PDA), pancreatic duct (PD) and pancreatic duct branch (PD-SB).

Vertical row at the bottom left: lumen, mucosa, submucosa, muscular.

Color map identification at the bottom right (origin and lesions):

A 35-year-old man with a history of alcohol abuse, paraduodenal pancreatitis (PDP) [also known as grooved pancreatitis].

(A) Axial contrast-enhanced CT images showing low density of enlarged PDG (white arrow), slight lateral duodenal wall thickening (black arrow), and slight inward shift of the pancreatic head (white arrow).

(B) Coronal CT image showing PDG enlargement (white arrows) and multiple small round cysts (black arrows)
along the medial wall of the descending duodenum.
Note the narrowing
of the duodenal lumen.
(C) Axial FS-T2WI showed abnormal hyperintensity (arrows) around the head of the pancreas and duodenum, the distribution was consistent with that shown on CT, and multiple cysts (arrows)
were seen on PDG and the inner wall of the duodenum.
(D-F) Pre-enhancement (D), early enhancement (E), late enhancement (F) T1WI showed delayed strengthening of T1 low signal foci (white arrows) in PDG, consistent with
fibrosis.
Asymmetrical thickening of the inner wall of the duodenum (arrow) (E) and CBD (arrow) (F)
of normal pipe diameter can be seen.
62-year-old man with pancreatic ductal adenocarcinoma (PDAC).

(A) Axial contrast-enhanced CT images showing weakly enhanced PDG masses (white arrows) directly invading the medial duodenal wall (black arrow) and IVC (white arrow).

Note that the CBD pipe diameter is normal (black arrow).

(B) Coronal enhanced CT image showing PDG (white arrow) has a weakly strengthened mass inseparable from the duodenum, morphologically irregular (arrow), associated with
direct invasion.
Note metastatic periportal swollen lymph nodes (*), normal diameter of the CBD and pancreatic ducts (black arrows), consistent with PDAC medial to the head of the pancreas, and no involvement of the biliary pancreatico
.
55-year-old female with duodenal adenocarcinoma
.
(A) Axial contrast-enhanced CT image showing heterogeneous enhanced mass (white arrow)
centered on duodenum and PDG.
The pancreatic duct is normal (black arrow).

(B) Coronal contrast-enhanced CT image showing thickened and weakly strengthened mass in the descending duodenal wall, marked narrowing of the corresponding intestinal lumen (white arrow), obstruction caused by an "apple core"-like lesion, and marked dilation of the stomach and duodenal bulb (black arrow).

(C) Another case, ampullary adenocarcinoma
.
Coronal contrast-enhanced CT images show a weakly strengthened foci along the ampullary area along the medial wall of the descending duodenum (black arrow) with dilated common bile duct (CBD) (white arrow) and pancreatic duct (black arrow), manifesting as a "double duct sign
.
"

Complications
of pancreatitis.

(A) Pancreatic pseudocyst.

Axial CT non-contrast image (oral contrast medium) shows a circular low-density foci (white arrow) on the medial wall of the duodenum, the duodenal lumen containing oral contrast is compressed and narrowed, crescent-shaped (black arrow), and attention is paid to calcifications in the parenchymal pancreas (black arrow), suggesting chronic pancreatitis
.

(B, C) Necrotizing pancreatitis
.
Axial T2WI(B) showed hyperintense accumulation of fluid and debris (arrows) instead of normal pancreatic parenchyma, and axial contrast enhancement T1WI(C) showed no strengthening
except for thick cyst walls (arrows).
Note the mass effect (arrows)
of the lesion on the descending duodenum.

(D) Mass-type chronic pancreatitis
.
Axial FS-T2WI shows a lump-like enlargement of the head of the pancreas (white arrow), and the normal diameter of the pancreatic duct (black arrow) passes through the mass and is mildly irregular (white arrow), manifested as a "penetrating duct sign"
.
Duodenal inflammation
.

(A) Crohn's disease
.
Coronal contrast-enhanced CT images show thickening of the duodenal wall with mucosal strengthening (black arrows), submucosal edema of low density, and opacity of the periduodenal fat space (white arrows).

Note that edema extends to the lower edge of PDG (black arrow).

(B) Peptic ulcer
.
Axial contrast-enhanced CT image showing duodenal wall thickening and surrounding space clouding (white arrow).

A small low-density foci on the inner wall of the duodenum with fluid and a little gas (black arrow) suggests an ulcer
.

47-year-old man with leiomyosarcoma
.
(A) Axial contrast-enhanced CT images showing aggressive, heterogeneously enhanced lower density masses (white arrows) behind the peritoneum, involving IVC (white arrows), protruding into PDG, duodenum, and pancreatic head (black arrows) moving forward, which helps to determine that the mass originates dorsally rather than within
the PDG.
(B) Coronary CT enhanced image showing IVC intraluminal cancer thrombus (white arrow) extending to the right renal vein (black arrow).

52-year-old woman with a history of abdominal trauma and multiple decombriomas
.
(A) Coronal CT enhanced image showing a uniform weakly reinforced foci (white arrow) on the medial side of the descending duodenum and a well-demarcated large mass (black arrow)
in the right lower abdomen.
(B) Axial contrast enhancement CT image showing that the mass (white arrow) is located medial and posterior to the PDG and has a mass effect on the IVC and left renal vein (black arrow).

36-year-old male with history of multiple endocrine neoplasia type 2 (MEN 2), multiple paraganglioma
.
(A) The axial enhancement arterial phase shows that the pancreas-duodenum (arrow) is compressed and forward, and a clearly heterogeneous reinforced mass (white*)
with a clear boundary behind it.
An even, well-strengthened mass (black*)
is also seen behind the left peritoneum.
(B) Axial T2WI showed hyperintensity, especially the mass (white*)
behind PDG.
41-year-old male with schwannoma
.
Axial contrast-enhanced CT image showing a well-defined, uniformly and weakly strengthened circular-like mass (white arrow) separating the anterior duodenum and pancreas (black arrow) and posterior IVC (white arrow), which is compressed and flattened
.
55-year-old female with a history of breast cancer, metastatic enlarged lymph nodes
.
(A) Axial contrast enhancement T1WI image shows weakly strengthened oval masses (arrows)
in PDG.
(B) DWI shows high signal of the mass (arrow) and low signal on the ADC plot, indicating limited
spread.
(C) PET/CT (FDG) images show markedly high metabolism of the mass (arrow), indicating significant radiotracer uptake
.
49-year-old male with metastatic duodenal neuroendocrine tumor (NET).

(A) Axial contrast-enhanced CT arterial phase images show a distinct oval strengthening foci (*) anterior to PDG, and a slight posterior shift of the head of the pancreas and duodenum (arrows).

(B) Coronary CT image showing a reinforced small nodular foci (white arrow) on the lateral wall of the duodenal bulb, confirmed as primary duodenal NET, see also micro-enhanced foci in the left lobe of the liver (black arrow).

The primary lesion is intensified to the same extent as
metastatic lymph nodes.

Periampullary duodenal diverticulum
.

(A-C) Lemmel syndrome (duodenal diverticulum obstructive jaundice syndrome).

Coronal (A) and axial (B) contrast-enhanced CT images show PDG showing an oval heterogeneous periampullary "mass" (arrow) obstructing CBD (white arrow).

The key to diagnosis is the presence of trace gases (black arrows)
in the diverticulum.
Coronal contrast-enhanced CT with oral and intravenous contrast (C) shows defects (arrows)
at the root of the diverticulum (white arrow) on the medial wall of the descending duodenum.

(D) Gastric outlet obstruction
.
Coronal contrast-enhanced CT with oral and intravenous contrast shows a class of round contrast-filled pouches (arrows) around the ampulla of PDG, which results in dilation of the stomach and duodenal bulbs (arrows).

(E) Gastrointestinal stones and pancreatitis
.
Axial contrast-enhanced CT and oral contrast showed PDG with a class of round lesions (arrows) containing mixed substances and gases
.
Note that extensive inflammatory exudation and fluid (arrows) may be seen in the sac area of the lesser omentum, consistent with
acute pancreatitis.

22-year-old man with duodenal repetitive cyst.

MRCP shows a lobular thick-walled cystic mass (arrow) that is not heterogeneous and hyperintensive
.
The mass protrudes into the duodenal lumen without direct communication
.

25-year-old female, common bile duct cyst (type III).

MRCP shows a cyst in the descending duodenal cavity (black arrow), a cyst in the ampulla that originates in the intramural part
of the common bile duct.
The remaining bile ducts and pancreatic ducts are normal
.
58-year-old male, annular pancreas
.
Axial contrast-enhanced CT with oral and intravenous contrast shows thicker fortified soft tissue (white arrow) enveloping the descending duodenum containing oral contrast, similar to thickening
of the duodenal wall.
Note that the head segment of the common bile duct pancreas (black arrow) is located on the inside of
the duodenum.

34-year-old male with lymphangiomality
.
(A) Axial T2WI shows a lobular hyperintense cystic mass (black arrow) in the anterior pararenal space, with internal septum and small cystic cavity, located between
IVC (black arrow) and descending duodenal segment (white arrow).
(B) Axial contrast enhancement shows no reinforcement of the lesion (arrows), and spacing is slightly strengthened (arrows).

Various vascular diseases
.

(A, B) pseudoaneurysms
secondary to peptic ulcers.
(A) Coronary CTA shows a small round highly fortified foci (arrow) near PDG with thickened inner duodenal wall around it, and a deep penetrating ulcer (arrow)
is seen.
(B) DSA shows a pseudoaneurysm (white arrow) originating from the gastroduodenal artery (white arrow) and active extravasation of contrast (black arrow) into the ulcer pit and duodenal lumen
.

(C) True aneurysm
.
Sagittal CTA shows a local dilation (arrow) of the gastroduodenal artery in front of the head of the pancreas (white arrow) near the PDG, and true aneurysms are common with peripheral calcifications (black arrows)
due to their chronic process.

(D) Spongy lesions in the portal vein
.
Coronal contrast-enhanced CT images show multiple chronically enhanced tortuous structures (arrows) in and around the head of the pancreas, secondary to chronic occlusion (arrows)
at the portal-mesenteric vein junction.
Trauma
.

(A) duodenal rupture
.
Axial CT non-contrast with oral contrast showed leakage into the PDG (arrow) and accumulation on the right side of the abdominal cavity, with gas visible in both the descending duodenal segment (*) and the abdominal cavity (white arrow).

(B, C) duodenal hematoma
.
(B) Axial T1WI-fs showed hyperintensity (arrows) in the descending duodenal and PDG regions, and pancreatic head inward shift (arrows).

(C) Axial T2WI shows a low-signal oval mass (arrow) with lower margins, the center of the lesion is located on the lateral wall of the descending duodenum, and a "claw sign" (arrow) is seen, and the duodenal lumen narrows into a crescent-shaped
shape.

74-year-old man with glioid pancreatic carcinoma
.
Coronal T2WI shows a cystic heterogeneous hyperintense mass (arrow) centered on the head of the pancreas, causing biliary obstruction (arrow).

Note that the pancreatic duct is markedly dilated (*), and the main pancreatic tube type IPMN is considered on endoscopy, which protrudes into the duodenal lumen and secretes a large amount of mucin
.

Duodenal GIST
.
Axial contrast-enhanced arterial phase CT images show a significantly enhanced peripherally enhanced mass in the PDG area
.
Lesions originate from the posterior medial wall of the descending duodenum, with most exophytes (white arrows) and a small portion convex into the cavity (black arrows).

Lesions involving the pancreaticoduodenal region (depending on etiology and organ of origin)

(Organs of origin: infection/inflammation; Tumor; Congenital; Vascular; Trauma; Obstruction)

PDG：

Pancreas:

Duodenum:

Bile duct:

Ampulla-nipple complex:

English abbreviations: AVM = arteriovenous malformation, GDA = gastroduodenal artery, GIST = gastrointestinal stromal tumor, IgA = immunoglobulin A, IgG4 = immunoglobulin G4, IPMN = intraductal papillary myxoma, IPNB = intraductal papilloma, MCN = myxocystic tumor, NA = not applicable, NET = neuroendocrine tumor, PDA = pancreaticoduodenal artery, PDP = paraduodenal pancreatitis (grooved pancreatitis), PV = portal vein, SCA = serous cystadenoma, SLE = systemic lupus erythema, SPEN = solid pseudopapillary epithelial tumor
.

A variety of inflammatory, structural, or neoplastic entities can affect PDG
.
Depending on the nature and location of the lesion, the effect on adjacent structures, and other relevant presentations, taking into account the histological diversity of the area, radiologists can narrow the differential diagnosis
.
It is important to provide accurate interpretation to guide the next steps in the clinic, from conservative treatment to biopsy and surgical intervention
.

Knowledge Points: