(Radiographics. 1999;19:5-24.)
© RSNA, 1999
MR Pancreatography: A Useful Tool for Evaluating Pancreatic Disorders
Ann S. Fulcher, MD1 and
Mary Ann Turner, MD1
1 Department of Radiology, Medical College of Virginia, Virginia Commonwealth University, 401 N 12th St, Richmond, VA 23298-0615.
 |
Abstract
|
|---|
Magnetic resonance (MR) pancreatography is being used with increasing frequency as a noninvasive alternative to diagnostic endoscopic retrograde pancreatography in the evaluation of the pancreatic duct and various pathologic conditions of the pancreas. This recently developed technique allows improved spatial resolution and permits imaging of the entire pancreaticobiliary tract during a single breath hold. MR pancreatography can help identify the course and drainage pattern of the pancreatic duct and is useful in diagnosing congenital anomalies such as pancreas divisum and annular pancreas without the risk of inducing pancreatitis. In some instances, MR pancreatography may demonstrate duct disruption and associated fluid collections resulting from trauma. In recurrent acute pancreatitis, MR pancreatography is useful in suggesting the cause of the disease; in chronic pancreatitis, it is useful in depicting ductal anatomy, detecting strictures or intraductal calculi prior to surgery, and detecting complications such as pseudocysts and fistulas. In addition, MR pancreatography performed in conjunction with abdominal MR imaging is useful in identifying pancreatic malignancies as well as in establishing resectability and preventing unnecessary preoperative stent placement.
Index Terms: Pancreas, abnormalities, 770.1491 • Pancreas, diseases, 770.245, 770.256, 770.3123 • Pancreas, injuries, 770.40 • Pancreas, neoplasms, 770.321 • Pancreatic ducts • Pancreatic ducts, MR, 774.1214 • Pancreatitis, 770.291
|
INTRODUCTION
|
|---|
Magnetic resonance (MR) pancreatography is a relatively new MR imaging technique that has emerged as an accurate, noninvasive means of evaluating the pancreatic duct. MR pancreatography makes use of heavily T2-weighted sequences that depict the fluid-containing pancreatic duct as a high-signal-intensity structure. Since its first clinical application more than 5 years ago, the technique has undergone a number of refinements such as the half-Fourier rapid acquisition with relaxation enhancement (RARE) sequence that have improved spatial resolution and contrast-to-noise ratios and have resulted in total examination times as short as 10 minutes (1,2). These refinements, together with increasing clinical and radiologic experience, have made MR pancreatography a viable alternative to diagnostic endoscopic retrograde pancreatography (ERP) in this context.
In this article, we describe and illustrate the use of MR pancreatography in the evaluation of the pancreatic duct and of pancreatic disease processes such as congenital anomalies, sequelae of traumatic injury, chronic pancreatitis and related complications, and neoplasms. The techniques and MR imaging findings described are based on our clinical experience with a series of 400 patients.
|
CLINICAL EXPERIENCE
|
|---|
MR pancreatography was performed in 400 patients with a 1.0-T (Magnetom Expert; Siemens, Erlangen, Germany) (n = 375) or 1.5-T (Magnetom Vision; Siemens) (n = 25) superconducting magnet programmed with the half-Fourier RARE sequence. A circularly polarized, phased-array surface coil was used. Antiperistaltic agents were not administered. MR pancreatograms were obtained as part of MR cholangiopancreatography with a previously described technique (3).
Our protocol begins with the acquisition of a coronal thick-slab (70-mm) scout image of the upper abdomen to localize the pancreatic duct and determine its orientation in the abdomen (Fig 1a) (Table 1). The pancreatic duct is localized with this scout image (Fig 1b), and a thick-slab (70-mm) axial image is acquired through the duct.The axial image is used throughout the examination as a guide for prescribing the appropriate angles for imaging the pancreatic duct with thin-slab (3–5-mm) sections in the coronal-oblique plane (Fig 1c) parallel to the duct in the pancreatic head, body, and tail. Although the majority of MR pancreatograms are obtained in the coronal-oblique plane, imaging is performed in the axial and axial-oblique planes at times for optimal delineation of ductal disease. The half-Fourier RARE sequence allows performance of thin-slab, multisection MR pancreatography such that 13 images of the pancreatic duct are acquired during an 18–20-second breath hold (Table 2).
View larger version (109K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1a. MR pancreatographic technique. (a) Coronal thick-slab scout image of the abdomen demonstrates the pancreatic duct (arrows) and biliary tract (arrowheads). (b) Coronal thick-slab scout image with a localizer (arrow) placed in the region of the pancreatic duct demarcates the area through which an axial thick-slab image will be obtained. (c) Axial thick-slab scout image obtained at the level of the pancreatic duct serves as a guide for prescribing angles (arrows) for obtaining thin-slab images of the duct in the coronal-oblique plane.
|
|
View larger version (121K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1b. MR pancreatographic technique. (a) Coronal thick-slab scout image of the abdomen demonstrates the pancreatic duct (arrows) and biliary tract (arrowheads). (b) Coronal thick-slab scout image with a localizer (arrow) placed in the region of the pancreatic duct demarcates the area through which an axial thick-slab image will be obtained. (c) Axial thick-slab scout image obtained at the level of the pancreatic duct serves as a guide for prescribing angles (arrows) for obtaining thin-slab images of the duct in the coronal-oblique plane.
|
|
View larger version (116K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1c. MR pancreatographic technique. (a) Coronal thick-slab scout image of the abdomen demonstrates the pancreatic duct (arrows) and biliary tract (arrowheads). (b) Coronal thick-slab scout image with a localizer (arrow) placed in the region of the pancreatic duct demarcates the area through which an axial thick-slab image will be obtained. (c) Axial thick-slab scout image obtained at the level of the pancreatic duct serves as a guide for prescribing angles (arrows) for obtaining thin-slab images of the duct in the coronal-oblique plane.
|
|
Because the pancreatic duct is often oriented obliquely in the abdomen, it is usually not seen in its entirety on any one thin-slab image. However, by reviewing all source images, one can visualize the entire duct. Although diagnostic decisions are made on the basis of the thin-slab source images, maximum-intensity projections and multiplanar reformatted images often allow depiction of a greater length of duct on a single image than on any one thin-slab source image (Fig 2). In addition, maximum-intensity projections and multiplanar reformatted images are useful in the three-dimensional depiction of ductal anatomy and in planning surgical procedures and radiation therapy.
|
NORMAL AND VARIANT PANCREATIC DUCTAL ANATOMY
|
|---|
The normal pancreatic duct measures 2–3 mm in caliber and demonstrates smooth margins (Fig 2). The caliber of the duct increases slightly from the pancreatic tail to the head. The pancreatic duct receives 20–35 short tributaries that enter at right angles. These tributaries or side branches are not usually seen at MR pancreatography unless they are dilated.
In our experience, MR pancreatograms generated with the half-Fourier RARE multisection technique permit visualization of the entire normal-caliber pancreatic duct in the head and body in 97% of cases and in the tail in 83% of cases (3). Complete visualization of a dilated pancreatic duct is possible in 100% of cases.
The pancreatic duct course varies greatly (Fig 3) but is most commonly a descending course (50% of cases). Other courses include sigmoid, vertical, and loop configurations. It is important to be familiar with the various courses of the pancreatic duct because they may be mistaken for pathologic conditions such as extrinsic mass effect from neoplastic disease. When the pancreatic duct is oriented vertically, it may be confused with the extrahepatic bile duct (Fig 4). At the point of embryologic fusion of the ducts of Santorini and Wirsung in the pancreatic neck, the duct may narrow slightly or demonstrate a loop that may be confused with a stricture (Figs 3d, 5).
View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4a. Vertically oriented pancreatic duct detected incidentally in a 72-year-old man with abdominal pain. (a) MR cholangiopancreatogram reveals a vertically oriented pancreatic duct (arrows) mimicking the distal bile duct. The gallbladder (arrowheads) is seen adjacent to the pancreatic duct. (b) MR cholangiopancreatogram obtained 10 mm posterior to a depicts the course of the extrahepatic bile duct (arrows), which parallels that of the vertically oriented pancreatic duct (cf a). The gallbladder (arrowheads) and duodenal bulb (*) are also seen. (c) MR cholangiopancreatogram obtained 5 mm posterior to a shows the distal bile duct (arrow) lateral to the vertically oriented pancreatic duct (arrowheads). A fluid-filled periampullary diverticulum (*) is demonstrated incidentally.
|
|
View larger version (151K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4b. Vertically oriented pancreatic duct detected incidentally in a 72-year-old man with abdominal pain. (a) MR cholangiopancreatogram reveals a vertically oriented pancreatic duct (arrows) mimicking the distal bile duct. The gallbladder (arrowheads) is seen adjacent to the pancreatic duct. (b) MR cholangiopancreatogram obtained 10 mm posterior to a depicts the course of the extrahepatic bile duct (arrows), which parallels that of the vertically oriented pancreatic duct (cf a). The gallbladder (arrowheads) and duodenal bulb (*) are also seen. (c) MR cholangiopancreatogram obtained 5 mm posterior to a shows the distal bile duct (arrow) lateral to the vertically oriented pancreatic duct (arrowheads). A fluid-filled periampullary diverticulum (*) is demonstrated incidentally.
|
|
View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4c. Vertically oriented pancreatic duct detected incidentally in a 72-year-old man with abdominal pain. (a) MR cholangiopancreatogram reveals a vertically oriented pancreatic duct (arrows) mimicking the distal bile duct. The gallbladder (arrowheads) is seen adjacent to the pancreatic duct. (b) MR cholangiopancreatogram obtained 10 mm posterior to a depicts the course of the extrahepatic bile duct (arrows), which parallels that of the vertically oriented pancreatic duct (cf a). The gallbladder (arrowheads) and duodenal bulb (*) are also seen. (c) MR cholangiopancreatogram obtained 5 mm posterior to a shows the distal bile duct (arrow) lateral to the vertically oriented pancreatic duct (arrowheads). A fluid-filled periampullary diverticulum (*) is demonstrated incidentally.
|
|
View larger version (122K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5a. Loop configuration of the pancreatic duct in an 11-year-old girl with recurrent pancreatitis. (a) MR pancreatogram demonstrates a loop in the pancreatic duct (arrow) at the point of embryologic fusion of the ducts of Santorini and Wirsung. The loop mimics a stricture. (b) MR pancreatogram obtained at a slightly different angle shows the pancreatic duct in an uncoiled position (arrow) and excludes a stricture.
|
|
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5b. Loop configuration of the pancreatic duct in an 11-year-old girl with recurrent pancreatitis. (a) MR pancreatogram demonstrates a loop in the pancreatic duct (arrow) at the point of embryologic fusion of the ducts of Santorini and Wirsung. The loop mimics a stricture. (b) MR pancreatogram obtained at a slightly different angle shows the pancreatic duct in an uncoiled position (arrow) and excludes a stricture.
|
|
Because of its complex embryologic development, the pancreatic duct demonstrates multiple variations in drainage patterns (Figs 6–9). In 91% of individuals, the major drainage route of the pancreas is through the duct of Wirsung, which joins the bile duct at the major ampulla (4). This drainage route is formed by fusion of the duct draining the pancreatic body and tail with the duct draining the inferior pancreatic head and uncinate process (duct of Wirsung) (Fig 7). An accessory pancreatic duct (persistent duct of Santorini) that drains through the minor ampulla is present in 44% of individuals and demonstrates variable degrees of persistence (Figs 8, 9). Despite improvements in spatial resolution at MR pancreatography, it is unlikely that this technique can be used to distinguish absent from diminutive ducts of Santorini in all cases. The duct of Santorini provides the major drainage route in 9% of individuals (4). Complete failure of fusion of the ducts of the dorsal and ventral pancreas constitutes pancreas divisum.
View larger version (18K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6a. Variations in pancreatic duct drainage. Drawings illustrate the duct of Wirsung with atrophy of the duct of Santorini (a), persistent duct of Santorini with primary drainage through the duct of Wirsung (b), and isolation of the ducts of Wirsung and Santorini resulting in pancreas divisum (c).
|
|
View larger version (18K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6b. Variations in pancreatic duct drainage. Drawings illustrate the duct of Wirsung with atrophy of the duct of Santorini (a), persistent duct of Santorini with primary drainage through the duct of Wirsung (b), and isolation of the ducts of Wirsung and Santorini resulting in pancreas divisum (c).
|
|
View larger version (18K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6c. Variations in pancreatic duct drainage. Drawings illustrate the duct of Wirsung with atrophy of the duct of Santorini (a), persistent duct of Santorini with primary drainage through the duct of Wirsung (b), and isolation of the ducts of Wirsung and Santorini resulting in pancreas divisum (c).
|
|
View larger version (131K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9a. Duct of Wirsung and diminutive duct of Santorini in a 51-year-old man with acute pancreatitis. (a) MR cholangiopancreatogram shows the major drainage route of the pancreas through the duct of Wirsung (arrow) at the major ampulla. Note the distal bile duct (arrowheads). (b) MR cholangiopancreatogram obtained 5 mm anterior to a reveals a persistent but diminutive duct of Santorini (arrow) entering the minor ampulla cephalad to the duct of Wirsung (arrowheads).
|
|
View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9b. Duct of Wirsung and diminutive duct of Santorini in a 51-year-old man with acute pancreatitis. (a) MR cholangiopancreatogram shows the major drainage route of the pancreas through the duct of Wirsung (arrow) at the major ampulla. Note the distal bile duct (arrowheads). (b) MR cholangiopancreatogram obtained 5 mm anterior to a reveals a persistent but diminutive duct of Santorini (arrow) entering the minor ampulla cephalad to the duct of Wirsung (arrowheads).
|
|
View larger version (153K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7. Figures 7, 8. (7) Duct of Wirsung and absent duct of Santorini in a 47-year-old woman with cirrhosis who was referred for MR imaging and MR cholangiopancreatography prior to undergoing liver transplantation. MR cholangiopancreatogram demonstrates drainage of the pancreas through the duct of Wirsung (arrow), which joins with the distal bile duct (arrowheads) to enter the major ampulla. Note the absence of the duct of Santorini. (8) Duct of Wirsung and persistent duct of Santorini in a 61-year-old woman with abdominal pain. (a) MR cholangiopancreatogram shows a persistent duct of Santorini (arrow) entering the minor ampulla and lying cephalad to the duct of Wirsung. (b) MR cholangiopancreatogram obtained posterior to a demonstrates the distal bile duct (arrowhead) extending caudad to the partially visualized duct of Santorini (arrow).
|
|
View larger version (155K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8a. Figures 7, 8. (7) Duct of Wirsung and absent duct of Santorini in a 47-year-old woman with cirrhosis who was referred for MR imaging and MR cholangiopancreatography prior to undergoing liver transplantation. MR cholangiopancreatogram demonstrates drainage of the pancreas through the duct of Wirsung (arrow), which joins with the distal bile duct (arrowheads) to enter the major ampulla. Note the absence of the duct of Santorini. (8) Duct of Wirsung and persistent duct of Santorini in a 61-year-old woman with abdominal pain. (a) MR cholangiopancreatogram shows a persistent duct of Santorini (arrow) entering the minor ampulla and lying cephalad to the duct of Wirsung. (b) MR cholangiopancreatogram obtained posterior to a demonstrates the distal bile duct (arrowhead) extending caudad to the partially visualized duct of Santorini (arrow).
|
|
View larger version (144K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8b. Figures 7, 8. (7) Duct of Wirsung and absent duct of Santorini in a 47-year-old woman with cirrhosis who was referred for MR imaging and MR cholangiopancreatography prior to undergoing liver transplantation. MR cholangiopancreatogram demonstrates drainage of the pancreas through the duct of Wirsung (arrow), which joins with the distal bile duct (arrowheads) to enter the major ampulla. Note the absence of the duct of Santorini. (8) Duct of Wirsung and persistent duct of Santorini in a 61-year-old woman with abdominal pain. (a) MR cholangiopancreatogram shows a persistent duct of Santorini (arrow) entering the minor ampulla and lying cephalad to the duct of Wirsung. (b) MR cholangiopancreatogram obtained posterior to a demonstrates the distal bile duct (arrowhead) extending caudad to the partially visualized duct of Santorini (arrow).
|
|
An anomalous union of the pancreatic and bile ducts is seen in 1.5%–3% of individuals (Fig 10). This anomalous union is characterized by an unusually long (15-mm) channel common to the two ducts that lies proximal to the sphincters of the pancreatic and bile ducts in the duodenal wall (5).
View larger version (156K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10. Anomalous union of the pancreatic and bile ducts detected incidentally in a 74-year-old woman. MR cholangiopancreatogram shows a 1.6-cm-long channel (straight arrow) common to the duct of Wirsung (curved arrow) and the distal bile duct (arrowhead).
|
|
|
CONGENITAL ANOMALIES
|
|---|
MR pancreatography is useful in diagnosing congenital anomalies of the pancreatic duct without the risk of inducing pancreatitis. Recent technical advances have resulted in improved spatial resolution that permits visualization of ducts as small as 1 mm in diameter (3).
Pancreas Divisum
Embryologically, the pancreas forms from a ventral anlage that becomes the inferior pancreatic head and uncinate process and from a dorsal anlage that becomes the superior pancreatic head and the body and tail of the pancreas (6). At 7 weeks gestation, the two anlagen fuse, and in over 90% of cases their ducts fuse as well. The duct draining the dorsal anlage joins with that draining the ventral anlage to enter the major ampulla with the bile duct. Thus, the main route of pancreatic drainage is established through the duct of Wirsung at the major ampulla. In 5.5%–7.5% of cases, the ducts of the dorsal and ventral anlagen do not fuse, resulting in pancreas divisum (Fig 11) (4,7). Although this variant may be detected incidentally in asymptomatic patients, pancreas divisum occurs more frequently in patients who present with acute idiopathic pancreatitis than in the general population (7). In the past, the presence of pancreas divisum was established with ERP. However, because of the risk of inducing or exacerbating pancreatitis, MR pancreatography is being used with increasing frequency in the evaluation of patients with suspected pancreas divisum. Bret et al (8) reported an accuracy of 100% for MR pancreatography in the diagnosis of pancreas divisum.
View larger version (139K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11a. Pancreas divisum in a 62-year-old woman with recurrent pancreatitis. (a) MR cholangiopancreatogram demonstrates the distal bile duct (arrow) joining with the ventral pancreatic duct (arrowhead) to enter the major ampulla. (b) MR cholangiopancreatogram obtained 5 mm anterior to a shows the dorsal pancreatic duct (arrows), which is located anterior and superior to the ventral pancreatic duct (cf a). (c) Axial MR cholangiopancreatogram demonstrates the isolated ventral (arrow) and dorsal (arrowhead) pancreatic ducts. (d) Endoscopic retrograde cholangiopancreatogram obtained after injection of contrast material into the ventral duct (arrow) shows arborization of the duct. Residual contrast material from a prior injection at the minor ampulla is seen in the dorsal pancreatic duct (arrowheads).
|
|
View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11b. Pancreas divisum in a 62-year-old woman with recurrent pancreatitis. (a) MR cholangiopancreatogram demonstrates the distal bile duct (arrow) joining with the ventral pancreatic duct (arrowhead) to enter the major ampulla. (b) MR cholangiopancreatogram obtained 5 mm anterior to a shows the dorsal pancreatic duct (arrows), which is located anterior and superior to the ventral pancreatic duct (cf a). (c) Axial MR cholangiopancreatogram demonstrates the isolated ventral (arrow) and dorsal (arrowhead) pancreatic ducts. (d) Endoscopic retrograde cholangiopancreatogram obtained after injection of contrast material into the ventral duct (arrow) shows arborization of the duct. Residual contrast material from a prior injection at the minor ampulla is seen in the dorsal pancreatic duct (arrowheads).
|
|
View larger version (117K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11c. Pancreas divisum in a 62-year-old woman with recurrent pancreatitis. (a) MR cholangiopancreatogram demonstrates the distal bile duct (arrow) joining with the ventral pancreatic duct (arrowhead) to enter the major ampulla. (b) MR cholangiopancreatogram obtained 5 mm anterior to a shows the dorsal pancreatic duct (arrows), which is located anterior and superior to the ventral pancreatic duct (cf a). (c) Axial MR cholangiopancreatogram demonstrates the isolated ventral (arrow) and dorsal (arrowhead) pancreatic ducts. (d) Endoscopic retrograde cholangiopancreatogram obtained after injection of contrast material into the ventral duct (arrow) shows arborization of the duct. Residual contrast material from a prior injection at the minor ampulla is seen in the dorsal pancreatic duct (arrowheads).
|
|
View larger version (106K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11d. Pancreas divisum in a 62-year-old woman with recurrent pancreatitis. (a) MR cholangiopancreatogram demonstrates the distal bile duct (arrow) joining with the ventral pancreatic duct (arrowhead) to enter the major ampulla. (b) MR cholangiopancreatogram obtained 5 mm anterior to a shows the dorsal pancreatic duct (arrows), which is located anterior and superior to the ventral pancreatic duct (cf a). (c) Axial MR cholangiopancreatogram demonstrates the isolated ventral (arrow) and dorsal (arrowhead) pancreatic ducts. (d) Endoscopic retrograde cholangiopancreatogram obtained after injection of contrast material into the ventral duct (arrow) shows arborization of the duct. Residual contrast material from a prior injection at the minor ampulla is seen in the dorsal pancreatic duct (arrowheads).
|
|
Annular Pancreas
Annular pancreas is seen in one of every 20,000 autopsies and is characterized by pancreatic tissue completely or incompletely surrounding the duodenum, most commonly the descending duodenum. In complete annular pancreas, patients present during the neonatal stage. However, patients with incomplete or partial annular pancreas may not present until adulthood. In some instances, incomplete annular pancreas is detected incidentally. Although this anomaly may be recognized at conventional radiography, upper gastrointestinal series, or computed tomography (CT), only ERP has allowed definitive diagnosis (9). More recently, annular pancreas has been diagnosed with MR imaging and MR pancreatography by identifying the pancreatic annulus and the duct within the annulus that surrounds all or part of the duodenum (Fig 12) (10,11).
View larger version (154K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12a. Annular pancreas detected incidentally in a 61-year-old man in whom cannulation of the bile duct was not possible during endoscopic retrograde cholangiopancreatography. The patient was referred for MR cholangiography for ductal delineation. (a) MR pancreatogram shows the curvilinear duct (arrows) in the annular pancreas. (b) Endoscopic retrograde cholangiograph helps confirm the annular pancreatic duct (arrows). (c) Coronal T1-weighted, fat-suppressed abdominal MR image (repetition time msec/effective echo time msec = 200/ 4.4) demonstrates the annular pancreas (arrows) lying lateral to the fluid-filled duodenum (arrowhead).
|
|
View larger version (126K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12b. Annular pancreas detected incidentally in a 61-year-old man in whom cannulation of the bile duct was not possible during endoscopic retrograde cholangiopancreatography. The patient was referred for MR cholangiography for ductal delineation. (a) MR pancreatogram shows the curvilinear duct (arrows) in the annular pancreas. (b) Endoscopic retrograde cholangiograph helps confirm the annular pancreatic duct (arrows). (c) Coronal T1-weighted, fat-suppressed abdominal MR image (repetition time msec/effective echo time msec = 200/ 4.4) demonstrates the annular pancreas (arrows) lying lateral to the fluid-filled duodenum (arrowhead).
|
|
View larger version (155K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12c. Annular pancreas detected incidentally in a 61-year-old man in whom cannulation of the bile duct was not possible during endoscopic retrograde cholangiopancreatography. The patient was referred for MR cholangiography for ductal delineation. (a) MR pancreatogram shows the curvilinear duct (arrows) in the annular pancreas. (b) Endoscopic retrograde cholangiograph helps confirm the annular pancreatic duct (arrows). (c) Coronal T1-weighted, fat-suppressed abdominal MR image (repetition time msec/effective echo time msec = 200/ 4.4) demonstrates the annular pancreas (arrows) lying lateral to the fluid-filled duodenum (arrowhead).
|
|
Anomalous Union of the Pancreatic and Bile Ducts
The anomalous union of the pancreatic and bile ducts described earlier occurs in association with choledochal cysts in 33%–83% of cases (Fig 13) (5). It has been postulated that this anomalous union allows reflux of pancreatic enzymes into the bile duct, thus weakening the bile duct wall and predisposing the patient to development of a choledochal cyst. Gallbladder carcinoma also occurs more frequently in patients with an anomalous union than in those without such a union.
View larger version (161K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13. Anomalous union of the pancreatic and bile ducts with associated type 1 choledochal cyst in a 25-year-old woman. Coronal non–fat-suppressed RARE image ( /60) reveals an anomalous union of the pancreatic and bile ducts (arrowhead) associated with a choledochal cyst (arrows).
|
|
|
SEQUELAE OF TRAUMATIC INJURY
|
|---|
Traumatic injuries of the pancreatic duct may be related to penetrating or blunt trauma. The pancreatic duct may also be injured during surgery, particularly splenectomy. In the acute setting, suspected pancreatic disruption is often evaluated with ERP. Barkin et al (12) reported a sensitivity and specificity of 100% for ERP for the detection of pancreatic duct disruption. In our experience, however, ERP does not help identify disruption in all cases. In some instances, MR pancreatography may show the duct disruption as well as associated fluid collections (Fig 14).
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14a. Acute disruption of the pancreatic duct in a 39-year-old man. The patient presented with left upper quadrant pain and hyperamylasemia after sustaining extensive splenic lacerations in a motor vehicle accident. Splenectomy was performed 1 week prior to MR pancreatography. (a) Scout MR cholangiopancreatogram demonstrates the pancreatic duct (arrowheads) terminating in an 8-mm fluid collection (arrow) in the pancreatic tail. An adjacent pseudocyst (*) is also seen. (b) Coronal non–fat-suppressed RARE image (/60) helps confirm the 8-mm fluid collection in the pancreatic tail (arrow), indicating ductal disruption. The disrupted duct was confirmed at surgery and shown to communicate with the pseudocyst (*). (c) Endoscopic retrograde cholangiopancreatogram shows complete filling of the pancreatic duct (arrows) but no evidence of the fluid collection and duct disruption noted at MR cholangiopancreatography.
|
|
View larger version (156K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14b. Acute disruption of the pancreatic duct in a 39-year-old man. The patient presented with left upper quadrant pain and hyperamylasemia after sustaining extensive splenic lacerations in a motor vehicle accident. Splenectomy was performed 1 week prior to MR pancreatography. (a) Scout MR cholangiopancreatogram demonstrates the pancreatic duct (arrowheads) terminating in an 8-mm fluid collection (arrow) in the pancreatic tail. An adjacent pseudocyst (*) is also seen. (b) Coronal non–fat-suppressed RARE image (/60) helps confirm the 8-mm fluid collection in the pancreatic tail (arrow), indicating ductal disruption. The disrupted duct was confirmed at surgery and shown to communicate with the pseudocyst (*). (c) Endoscopic retrograde cholangiopancreatogram shows complete filling of the pancreatic duct (arrows) but no evidence of the fluid collection and duct disruption noted at MR cholangiopancreatography.
|
|
View larger version (108K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14c. Acute disruption of the pancreatic duct in a 39-year-old man. The patient presented with left upper quadrant pain and hyperamylasemia after sustaining extensive splenic lacerations in a motor vehicle accident. Splenectomy was performed 1 week prior to MR pancreatography. (a) Scout MR cholangiopancreatogram demonstrates the pancreatic duct (arrowheads) terminating in an 8-mm fluid collection (arrow) in the pancreatic tail. An adjacent pseudocyst (*) is also seen. (b) Coronal non–fat-suppressed RARE image (/60) helps confirm the 8-mm fluid collection in the pancreatic tail (arrow), indicating ductal disruption. The disrupted duct was confirmed at surgery and shown to communicate with the pseudocyst (*). (c) Endoscopic retrograde cholangiopancreatogram shows complete filling of the pancreatic duct (arrows) but no evidence of the fluid collection and duct disruption noted at MR cholangiopancreatography.
|
|
Injury of the pancreatic duct resulting from blunt trauma usually involves that portion of the duct in the pancreatic body that lies anterior to the vertebral body. This portion of the duct is relatively fixed and compressed against the vertebra during trauma. Such injury may manifest as duct disruption and leakage of fluid in the acute setting. If this injury goes unrecognized, a posttraumatic ductal stricture may occur with subsequent dilatation of the duct proximal to the stricture (Fig 15).
View larger version (131K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 15a. Stricture of the pancreatic duct resulting from trauma in a 68-year-old woman with abdominal pain and pancreatitis. The patient had experienced severe blunt abdominal trauma 17 years earlier. (a) Coronal MR cholangiopancreatogram demonstrates a normal-caliber pancreatic duct in the head, neck, and distal body of the pancreas (arrows). Marked ductal dilatation in the remainder of the pancreas (arrowheads) is present due to stricture formation. (b) Axial MR pancreatogram shows an abrupt point of transition between the normal pancreatic duct (arrow) and the dilated duct (arrowheads) in the body and tail of the pancreas.
|
|
View larger version (132K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 15b. Stricture of the pancreatic duct resulting from trauma in a 68-year-old woman with abdominal pain and pancreatitis. The patient had experienced severe blunt abdominal trauma 17 years earlier. (a) Coronal MR cholangiopancreatogram demonstrates a normal-caliber pancreatic duct in the head, neck, and distal body of the pancreas (arrows). Marked ductal dilatation in the remainder of the pancreas (arrowheads) is present due to stricture formation. (b) Axial MR pancreatogram shows an abrupt point of transition between the normal pancreatic duct (arrow) and the dilated duct (arrowheads) in the body and tail of the pancreas.
|
|
|
PANCREATITIS AND RELATED COMPLICATIONS
|
|---|
Pancreatitis is the most common benign disease involving the pancreas. Pancreatitis is classified as acute or chronic on the basis of clinical, morphologic, and histologic criteria. Acute pancreatitis is characterized by abdominal pain and elevation of serum amylase and lipase levels. In the evaluation of an initial episode of acute pancreatitis, MR cholangiopancreatography is focused primarily on the noninvasive detection or exclusion of choledocholithiasis. In patients who present with recurrent acute pancreatitis, MR pancreatography is useful in suggesting the cause of the disease (eg, pancreas divisum) (13). In patients with chronic pancreatitis, MR pancreatography is useful in depicting ductal anatomy, detecting strictures or intraductal calculi prior to surgery, and detecting complications such as pseudocysts and fistulas (14,15).
Ductal Manifestations of Pancreatitis
In acute pancreatitis, the pancreatic duct is smooth in contour but may be slightly compressed by the edematous pancreas. In contrast, chronic pancreatitis represents irreversible exocrine damage to the pancreas and irreversible morphologic changes in the pancreas and pancreatic duct. The morphologic changes in the duct that have been demonstrated with ERP and CT are also detected with MR pancreatography (16,17). These changes include dilatation of the main pancreatic duct and its side branches and contour irregularities (Figs 16, 17). In severe cases, the marked dilatation of the side branches has a "chain of lakes" appearance. Additional pancreatic ductal changes include stricture formation and intraductal calculi (Figs 16, 18). Stones as small as 2 mm have been identified at MR pancreatography (3). However, it is likely that stones lying within normal-caliber or minimally dilated side branches of the main pancreatic duct may not be identified. Because of the underlying fibrosis in chronic pancreatitis, the bile duct may be narrowed as it traverses the pancreatic head (Figs 16, 17). Typically, bile duct strictures associated with chronic pancreatitis are smooth and tapered.
View larger version (138K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 16a. Figures 16, 17. (16) Pancreatic duct dilatation, intraductal calculi, and bile duct stricture in a 47-year-old man with alcohol-induced chronic pancreatitis. (a) MR pancreatogram demonstrates dilatation of the pancreatic duct (arrows) and its side branches. Multiple intraductal calculi (arrowheads) are also seen. (b) MR cholangiopancreatogram (obtained at a different angle to allow optimal delineation of the bile duct) shows a stricture of the intrapancreatic bile duct (arrow) resulting in intrahepatic bile duct dilatation. The dilated pancreatic duct within the pancreatic head (arrowhead) is also seen. (c) Endoscopic retrograde cholangiopancreatogram demonstrates pancreatic and biliary duct dilatation, the biliary stricture (arrow), and the intraductal stones (arrowheads). (17) Bile duct stricture and pancreatic duct dilatation in a 50-year-old man with a long history of alcohol abuse and newly developed elevation of alkaline phosphatase levels. Maximum-intensity projection of an MR cholangiopancreatogram shows a smooth, tapering stricture of the intrapancreatic bile duct (arrowhead), characteristic of chronic pancreatitis. The pancreatic duct (arrows) is dilated and tortuous. The gallbladder (*) is distended.
|
|
View larger version (159K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 16b. Figures 16, 17. (16) Pancreatic duct dilatation, intraductal calculi, and bile duct stricture in a 47-year-old man with alcohol-induced chronic pancreatitis. (a) MR pancreatogram demonstrates dilatation of the pancreatic duct (arrows) and its side branches. Multiple intraductal calculi (arrowheads) are also seen. (b) MR cholangiopancreatogram (obtained at a different angle to allow optimal delineation of the bile duct) shows a stricture of the intrapancreatic bile duct (arrow) resulting in intrahepatic bile duct dilatation. The dilated pancreatic duct within the pancreatic head (arrowhead) is also seen. (c) Endoscopic retrograde cholangiopancreatogram demonstrates pancreatic and biliary duct dilatation, the biliary stricture (arrow), and the intraductal stones (arrowheads). (17) Bile duct stricture and pancreatic duct dilatation in a 50-year-old man with a long history of alcohol abuse and newly developed elevation of alkaline phosphatase levels. Maximum-intensity projection of an MR cholangiopancreatogram shows a smooth, tapering stricture of the intrapancreatic bile duct (arrowhead), characteristic of chronic pancreatitis. The pancreatic duct (arrows) is dilated and tortuous. The gallbladder (*) is distended.
|
|
View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 16c. Figures 16, 17. (16) Pancreatic duct dilatation, intraductal calculi, and bile duct stricture in a 47-year-old man with alcohol-induced chronic pancreatitis. (a) MR pancreatogram demonstrates dilatation of the pancreatic duct (arrows) and its side branches. Multiple intraductal calculi (arrowheads) are also seen. (b) MR cholangiopancreatogram (obtained at a different angle to allow optimal delineation of the bile duct) shows a stricture of the intrapancreatic bile duct (arrow) resulting in intrahepatic bile duct dilatation. The dilated pancreatic duct within the pancreatic head (arrowhead) is also seen. (c) Endoscopic retrograde cholangiopancreatogram demonstrates pancreatic and biliary duct dilatation, the biliary stricture (arrow), and the intraductal stones (arrowheads). (17) Bile duct stricture and pancreatic duct dilatation in a 50-year-old man with a long history of alcohol abuse and newly developed elevation of alkaline phosphatase levels. Maximum-intensity projection of an MR cholangiopancreatogram shows a smooth, tapering stricture of the intrapancreatic bile duct (arrowhead), characteristic of chronic pancreatitis. The pancreatic duct (arrows) is dilated and tortuous. The gallbladder (*) is distended.
|
|
View larger version (136K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 17. Figures 16, 17. (16) Pancreatic duct dilatation, intraductal calculi, and bile duct stricture in a 47-year-old man with alcohol-induced chronic pancreatitis. (a) MR pancreatogram demonstrates dilatation of the pancreatic duct (arrows) and its side branches. Multiple intraductal calculi (arrowheads) are also seen. (b) MR cholangiopancreatogram (obtained at a different angle to allow optimal delineation of the bile duct) shows a stricture of the intrapancreatic bile duct (arrow) resulting in intrahepatic bile duct dilatation. The dilated pancreatic duct within the pancreatic head (arrowhead) is also seen. (c) Endoscopic retrograde cholangiopancreatogram demonstrates pancreatic and biliary duct dilatation, the biliary stricture (arrow), and the intraductal stones (arrowheads). (17) Bile duct stricture and pancreatic duct dilatation in a 50-year-old man with a long history of alcohol abuse and newly developed elevation of alkaline phosphatase levels. Maximum-intensity projection of an MR cholangiopancreatogram shows a smooth, tapering stricture of the intrapancreatic bile duct (arrowhead), characteristic of chronic pancreatitis. The pancreatic duct (arrows) is dilated and tortuous. The gallbladder (*) is distended.
|
|
View larger version (147K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 18a. Uncinate duct calculus mimicking distal bile duct calculus in a 74-year-old woman with acute pancreatitis. (a) Axial contrast material–enhanced CT scan reveals an intraductal high-attenuation focus at the junction of the inferior pancreatic head and uncinate process (arrow), suspicious for a distal common bile duct calculus. (b) MR cholangiopancreatogram demonstrates that the distal common bile duct (straight arrow) is free of calculi. Note the angular configuration of the extrahepatic bile duct (arrowheads), often seen in association with chronic pancreatitis. The pancreatic duct in the head (curved arrow) is identified. (c) MR pancreatogram obtained posterior to a shows a filling defect in the pancreatic duct in the uncinate process (arrow) representing a calculus and corresponding to the high-attenuation focus noted on the CT scan.
|
|
View larger version (132K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 18b. Uncinate duct calculus mimicking distal bile duct calculus in a 74-year-old woman with acute pancreatitis. (a) Axial contrast material–enhanced CT scan reveals an intraductal high-attenuation focus at the junction of the inferior pancreatic head and uncinate process (arrow), suspicious for a distal common bile duct calculus. (b) MR cholangiopancreatogram demonstrates that the distal common bile duct (straight arrow) is free of calculi. Note the angular configuration of the extrahepatic bile duct (arrowheads), often seen in association with chronic pancreatitis. The pancreatic duct in the head (curved arrow) is identified. (c) MR pancreatogram obtained posterior to a shows a filling defect in the pancreatic duct in the uncinate process (arrow) representing a calculus and corresponding to the high-attenuation focus noted on the CT scan.
|
|
View larger version (133K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 18c. Uncinate duct calculus mimicking distal bile duct calculus in a 74-year-old woman with acute pancreatitis. (a) Axial contrast material–enhanced CT scan reveals an intraductal high-attenuation focus at the junction of the inferior pancreatic head and uncinate process (arrow), suspicious for a distal common bile duct calculus. (b) MR cholangiopancreatogram demonstrates that the distal common bile duct (straight arrow) is free of calculi. Note the angular configuration of the extrahepatic bile duct (arrowheads), often seen in association with chronic pancreatitis. The pancreatic duct in the head (curved arrow) is identified. (c) MR pancreatogram obtained posterior to a shows a filling defect in the pancreatic duct in the uncinate process (arrow) representing a calculus and corresponding to the high-attenuation focus noted on the CT scan.
|
|
Pseudocysts
Pseudocysts are encapsulated pancreatic fluid collections that may occur in association with acute or chronic pancreatitis (Figs 19–21). Pseudocysts may be extrapancreatic (Figs 19, 21) or intrapancreatic (Fig 20) in location and range from large to minute in size. Fewer than 50% of pseudocysts fill with contrast material when it is injected into the pancreatic duct during ERP (18). In some instances, the ductal communication can be demonstrated with MR pancreatography. Although ERP has high specificity in the diagnosis of pseudocysts, it has low sensitivity due to variable communication with the duct. Therefore, MR pancreatography, MR imaging, and other cross-sectional imaging techniques have a higher sensitivity than ERP for the detection of noncommunicating pseudocysts (Fig 20). Some pseudocysts communicate with adjacent organs, including the duodenum (Fig 21), stomach, and spleen.
Although as many as 60% of pseudocysts may resolve spontaneously (19), others will become complicated by infection or hemorrhage. MR imaging and MR pancreatography are useful in demonstrating pseudocysts and possibly their ductal communications as well as in establishing the presence of associated hemorrhage without the risk of infecting the pseudocyst as may occur at ERP.
View larger version (155K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 19. Figures 19, 20. (19) Pseudocyst adjacent to the pancreatic tail in a 31-year-old man with chronic pancreatitis. MR pancreatogram reveals dilatation of the pancreatic duct and its side branches (arrows), which terminate in a pseudocyst (*) that is inseparable from the pancreatic tail (arrowhead). MR pancreatography was performed to delineate the ductal anatomy prior to pancreatojejunostomy. (20) Intrapancreatic pseudocyst in a 72-year-old woman with pancreatitis. (a) MR cholangiopancreatogram shows a pseudocyst (straight arrow) in the superior aspect of the pancreatic head, a normal-caliber main pancreatic duct (arrowheads), and ectatic side branches of the duct draining the uncinate process (curved arrow). The gallbladder (*) is seen lateral to the bile duct. (b) Endoscopic retrograde cholangiopancreatogram demonstrates a normal-caliber pancreatic duct (arrowheads) but does not opacify the pseudocyst. The ectatic side branches of the uncinate process duct (arrow) are also seen.
|
|
View larger version (136K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 21a. Intramural duodenal fluid collection communicating with the pancreatic duct in a 55-year-old man with a history of alcohol abuse who presented with acute pancreatitis, nausea, and vomiting. (a) MR pancreatogram shows a communication (solid arrow) between the main pancreatic duct (arrowheads) and the fluid collection (*) in the wall of the duodenum. The gallbladder (open arrow) is also seen. (b) MR cholangiogram demonstrates the complex intramural duodenal fluid collection (*), which has significantly narrowed the lumen of the descending duodenum (arrows). (c) Upper gastrointestinal series shows narrowing of the descending duodenum (arrows) caused by the intramural duodenal fluid collection.
|
|
Top
Abstract
INTRODUCTION
