AJR 2004; 183:1637-1644
© American Roentgen Ray Society
MRI of Pancreatitis and Its Complications: Part 1, Acute Pancreatitis
Frank H. Miller1,
Ana L. Keppke1,
Kshitij Dalal1,
John N. Ly2,
Vilim-Alan Kamler1 and
Gregory T. Sica3
1 Department of Radiology, Northwestern Memorial Hospital, Northwestern
University, The Feinberg School of Medicine, 676 N Saint Clair St., Ste. 800,
Chicago, IL 60611.
2 Department of Radiology, Saint Vincent Medical Imaging, Level 5, 438 Victoria
St., Darling Hurst, NSW 2010, Australia.
3 Diagnostic Imaging Center, Harvard Vanguard Medical Associates, 133 Brookline
Ave., 1st Fl., Boston, MA 02115.
Received April 2, 2004;
accepted after revision June 8, 2004.
Address correspondence to F. H. Miller.
Introduction
The diagnosis of acute pancreatitis is generally based on clinical and
laboratory findings; however, CT is the imaging technique of choice for
confirming the diagnosis and detecting complications
[1]. In an audit of 2,068
patients who underwent CT examinations at a large tertiary care hospital, Naik
et al. [2] found that acute
pancreatitis and its complications were the most common indication for
abdominal CT. Because patients with pancreatitis are often young and require
multiple follow-up CT examinations, substitution of MRI for CT in some
patients would reduce the collective radiation dose considerably. MRI can have
an important role in staging the severity of acute pancreatitis and may be
superior to other imaging techniques for the characterization of
peripancreatic collections
[3–5].
Vascular complications such as pseudoaneurysms and venous thrombosis may also
be detected. However, some patients have contraindications to MRI and its role
in imaging patients with severe pancreatitis is unclear because these patients
are often too ill to undergo multiple breath-hold sequences. In addition, cost
may be an issue.
Reports of MRI features of acute pancreatitis are limited. In this
pictorial essay, we discuss the MRI findings in patients with acute
pancreatitis.
MRI Technique
Multiple recent advances in abdominal MRI allow optimal imaging of the
pancreas. These include high-field-strength magnet systems, high-performance
gradients, phased-array body coils, power injectors, dynamic contrast-enhanced
breath-hold spoiled gradient-echo sequences with fat suppression, and the
development of MR cholangiopancreatography (MRCP). The use of breath-hold
sequences reduces respiratory and motion artifacts, which previously limited
the use of MRI. Examination times have been reduced markedly so that the total
acquisition time at our institution is currently less than 5 min with a
complete scanner time of less than 30 min
(Table 1). The most important
sequences for pancreatic evaluation are T1-weighted spoiled gradient echo with
fat suppression and dynamic imaging after IV administration of gadolinium
(Fig. 1A,
1B,
1C,
1D). On T1-weighted sequences
with fat suppression, the pancreas has high signal intensity relative to the
liver because of the presence of acinar proteins
(Fig. 1B). After IV gadolinium
is administered, the pancreas enhances maximally during the pancreatic
arterial phase (15–20 sec) (Fig.
1C). During the later phases, contrast material washes out and the
pancreas becomes isointense relative to the liver
(Fig. 1D).
View larger version (90K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C. —62-year-old man with normal pancreas on MRI. Axial enhanced
T1-weighted fat-suppressed spoiled gradient-echo image obtained during
arterial phase shows marked enhancement of pancreas relative to other
organs.
|
|
View larger version (93K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D. —62-year-old man with normal pancreas on MRI. Axial enhanced
T1-weighted fat-suppressed spoiled gradient-echo image obtained during venous
phase shows washout of contrast material from pancreas.
|
|
T2-weighted sequences are especially useful for the evaluation of the
biliary tract and pancreatic duct. These sequences can accurately depict
pseudocysts, fluid collections, gallstones, and choledocholithiasis (Fig.
2A,
2B). MRCP, which is based on
heavily T2-weighted sequences, depicts fluid such as bile with high signal
intensity. MRCP has a sensitivity that is similar to that of ERCP for the
depiction of biliary anatomy and abnormalities with the advantage of being
noninvasive and not exposing the patient to ionizing radiation or requiring
patient sedation. In addition, MRI is able to show the pancreatic duct
upstream from an obstruction and noncommunicating pseudocysts.
View larger version (119K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2A. —75-year-old woman with choledocholithiasis and abnormal
results on liver function tests. Coronal T2-weighted HASTE image shows
multiple signal-void stones (arrows) surrounded by
high-signal-intensity bile in common bile duct.
|
|
View larger version (108K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2B. —75-year-old woman with choledocholithiasis and abnormal
results on liver function tests. Axial T2-weighted HASTE image shows stone of
common bile duct (short arrow) and gallstones (long
arrow).
|
|
Imaging Findings of Acute Pancreatitis
In patients with mild acute pancreatitis, the signal intensity of the
pancreas may remain normal on T1-weighted fat-suppressed images. This
sequence, which is important for the evaluation of pancreatic masses and
chronic pancreatitis, is not sensitive for acute edema. Dynamic imaging after
gadolinium administration using power injectors allows detection of necrosis
and abnormal enhancement of the pancreas.
Typical findings of acute pancreatitis include an enlarged pancreas with
diminished or heterogeneous signal intensity on T1-weighted fat-suppressed
contrast-enhanced images and peripancreatic inflammation (Figs.
3A,
3B and
4A,
4B,
4C). Stranding of the
peripancreatic fat planes is best seen on the in-phase T1-weighted
gradient-echo sequence. In more severe cases, peripancreatic fluid collections
occur as a result of the release of pancreatic enzymes and are best depicted
on T2-weighted images (Figs.
4A,
4B,
4C and
5).
View larger version (98K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A. —69-year-old man with acute pancreatitis. Coronal enhanced
T1-weighted fat-suppressed spoiled gradient-echo image obtained during venous
phase shows enlarged pancreas with inflammation surrounding pancreatic tail
(arrow).
|
|
View larger version (87K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3B. —69-year-old man with acute pancreatitis. Coronal T2-weighted
RARE image shows relatively normal pancreatic duct (arrowhead) and
common bile duct (CBD). Note luminal narrowing of duodenum (arrows)
due to involvement by inflammation from pancreatitis. GB = gallbladder.
|
|
View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4A. —55-year-old woman with cholangiocarcinoma and pancreatitis
after ERCP. Axial T2-weighted HASTE image shows peripancreatic fluid
(arrows) and mildly increased signal intensity of pancreas due to
edema.
|
|
View larger version (107K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4B. —55-year-old woman with cholangiocarcinoma and pancreatitis
after ERCP. Axial T1-weighted fat-suppressed spoiled gradient-echo image shows
normal high signal intensity of pancreas. Note pancreatic signal intensity may
be normal on T1-weighted fat-suppressed spoiled gradient-echo sequence in
cases of uncomplicated acute pancreatitis as opposed to cases of cancer or
chronic pancreatitis when the pancreas has low-signal-intensity abnormalities.
Peripancreatic fluid is better seen on T2-weighted images.
|
|
View larger version (89K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4C. —55-year-old woman with cholangiocarcinoma and pancreatitis
after ERCP. Axial enhanced T1-weighted fat-suppressed spoiled gradient-echo
image obtained during arterial phase shows diffusely decreased pancreatic
enhancement compared with normal pancreas, which is shown in
Figure 1C.
|
|
View larger version (95K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5. —45-year-old woman with pancreatitis after ERCP. Axial
enhanced T1-weighted fat-suppressed spoiled gradient-echo image obtained
during venous phase shows heterogeneous pancreatic enhancement due to
pancreatitis with peripancreatic fluid and inflammation (straight
arrows). Fluid (curved arrow) is seen between pancreas and
splenic vein. P = pancreas.
|
|
Focal acute pancreatitis occurs in approximately 20% of the cases. In such
instances, careful evaluation to exclude the remote possibility of
adenocarcinoma simulating pancreatitis is recommended (Fig.
6A,
6B,
6C). In older patients with
unexplained pancreatitis, short-term follow-up MRI, ERCP, or biopsy may be
appropriate.
View larger version (85K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6A. —36-year-old man with metastatic pancreatic adenocarcinoma
mimicking acute pancreatitis. Axial T1-weighted fat-suppressed spoiled
gradient-echo image shows mild enlargement and decreased signal intensity of
body and tail of pancreas.
|
|
View larger version (85K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6B. —36-year-old man with metastatic pancreatic adenocarcinoma
mimicking acute pancreatitis. Axial T1-weighted fat-suppressed spoiled
gradient-echo image shows normal high signal intensity of pancreatic head.
|
|
View larger version (86K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6C. —36-year-old man with metastatic pancreatic adenocarcinoma
mimicking acute pancreatitis. Axial enhanced T1-weighted fat-suppressed
spoiled gradient-echo image obtained during venous phase shows decreased
enhancement of body and tail of pancreas. Mild peripancreatic inflammation is
present. Note abnormal soft tissue (arrow) to left of superior
mesenteric artery due to tumor.
|
|
Pseudocyst
MRI can accurately detect and characterize pseudocysts. Uncomplicated
pseudocysts are typically unilocular and encapsulated fluid collections that
exhibit high signal intensity on T2-weighted and low signal intensity on
T1-weighted sequences. ERCP is usually required to reveal communication
between a pseudocyst and the pancreatic duct, although sometimes it can be
seen on MRI [6] (Fig.
7A,
7B). Complicated pseudocysts
and other pancreatic collections may contain solid debris, which is best
depicted by MRI [4] (Fig.
8A,
8B,
8C).
View larger version (101K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7A. —50-year-old woman with gallstone pancreatitis. Axial enhanced
T1-weighted fat-suppressed spoiled gradient-echo image obtained during venous
phase shows large pseudocyst, which communicates with common bile duct.
Peripancreatic fluid is seen anterior to pancreatic tail. Marked
peripancreatic inflammatory changes (arrows) are seen.
|
|
View larger version (160K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7B. —50-year-old woman with gallstone pancreatitis. Radiograph
obtained after injection of contrast material into drainage catheter shows
contrast material is visible in common bile duct (arrow) consistent
with fistula.
|
|
View larger version (131K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8A. —60-year-old man with gallstone pancreatitis and pseudocyst.
Unenhanced axial CT scan shows lobulated pseudocyst (arrow) located
anteroinferior to pancreas. Internal content of pseudocyst is not well
characterized. IV contrast material was contraindicated because of poor renal
function.
|
|
View larger version (95K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8B. —60-year-old man with gallstone pancreatitis and pseudocyst.
Axial enhanced T1-weighted fat-suppressed spoiled gradient-echo image obtained
during arterial phase shows peripheral enhancement of pseudocyst
(arrow).
|
|
Pancreatic Necrosis
Severe acute pancreatitis occurs in approximately 20–30% of cases,
and it is usually associated with pancreatic necrosis and increased
complications and mortality. Determining the extent of necrosis is important
because it has significant correlation with patient prognosis
[7]. Necrotic pancreatic
tissue—unlike viable portions of pancreatic tissue—does not
enhance. On T2-weighted images, necrosis can be low signal intensity or when
liquefied, hyperintense [4,
5]. At times, necrosis may be
better identified on MRI than CT (Figs.
9A,
9B and
10A,
10B,
10C).
View larger version (88K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9A. —59-year-old man with history of pancreatitis and large
pseudocyst drained from lesser sac. Axial enhanced T1-weighted fat-suppressed
spoiled gradient-echo image obtained during venous phase shows lack of
enhancement of body and tail of pancreas (arrows), which is
consistent with pancreatic necrosis.
|
|
View larger version (79K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9B. —59-year-old man with history of pancreatitis and large
pseudocyst drained from lesser sac. Axial T2-weighted HASTE image shows
pancreas (arrows) is markedly hypointense from necrosis and not
hyperintense like fluid as it would be if it were a pseudocyst.
|
|
View larger version (145K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10A. —56-year-old man with history of acute myelogenous leukemia
treated by chemotherapy who presented with abdominal pain suspected to be
acute pancreatitis. Axial contrast-enhanced CT scan shows lack of enhancement
of multiple areas in pancreas (arrows). It is difficult to determine
whether this finding represents pancreatic necrosis, a dilated duct due to
obstruction, or intraductal papillary mucinous tumor. Mild peripancreatic
inflammation is present.
|
|
View larger version (117K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10B. —56-year-old man with history of acute myelogenous leukemia
treated by chemotherapy who presented with abdominal pain suspected to be
acute pancreatitis. Axial enhanced T1-weighted fat-suppressed spoiled
gradient-echo image obtained during venous phase shows nonenhancing necrotic
areas (arrows) in body and tail of pancreas.
|
|
View larger version (132K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10C. —56-year-old man with history of acute myelogenous leukemia
treated by chemotherapy who presented with abdominal pain suspected to be
acute pancreatitis. Axial T2-weighted HASTE image shows nonenhancing area is
neither simple fluid nor pancreatic duct because it is not bright on
T2-weighted image; instead, area is necrotic pancreas.
|
|
Pancreatic Abscess
Abscesses usually occur 4 weeks after the onset of acute pancreatitis and
can appear similar to pseudocysts. They are suggested when gas is present in a
pancreatic or peripancreatic collection (Fig.
11A,
11B). MRI can reveal
air–fluid levels or large pockets of gas, but CT is more sensitive for
small collections of gas.
View larger version (93K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11A. —52-year-old man with acute pancreatitis and abscess. Axial
enhanced T1-weighted fat-suppressed spoiled gradient-echo image obtained
during venous phase shows irregular enhancement of wall of abscess. Note gas
bubble (arrow) within abscess.
|
|
Hemorrhage and Pseudoaneurysm
Hemorrhage can occur in patients with severe necrotizing pancreatitis or as
a result of the rupture of a pseudoaneurysm when it constitutes a
life-threatening emergency. Hemorrhagic fluid collections are more evident on
MRI than CT because of the following: high-signal-intensity methemoglobin on
T1-weighted images, low-signal-intensity hemosiderin rim on T2-weighted
images, and signal abnormalities due to hemorrhage remaining visible longer on
MRI than on CT
[3–5]
(Fig. 12A,
12B).
View larger version (83K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12A. —55-year-old woman with history of pancreatitis and
pseudocyst. Axial T1-weighted fat-suppressed spoiled gradient-echo image shows
high-signal-intensity abnormality (arrow) from hemorrhagic fluid
within pseudocyst in pancreatic tail.
|
|
View larger version (83K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12B. —55-year-old woman with history of pancreatitis and
pseudocyst. Axial T2-weighted HASTE image shows low-signal-intensity rim
(arrow) in pseudocyst. Diagnosis of hemorrhage is easily made on MRI
due to hemosiderin rim.
|
|
Pseudoaneurysms result from weakening of the vessel wall by pancreatic
proteolytic enzymes. They most frequently involve the splenic, gastroduodenal,
and pancreaticoduodenal arteries. Contrast-enhanced sequences confirm the
diagnosis by showing enhancement of the pseudoaneurysm comparable to arteries
and its connection to the vessels (Fig.
13).
View larger version (99K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13. —45-year-old woman with history of acute pancreatitis and
splenic artery pseudoaneurysm. Axial enhanced T1-weighted fat-suppressed
spoiled gradient-echo image shows splenic artery pseudoaneurysm
(arrow) enhancing similar to arteries.
|
|
Venous Thrombosis
Venous thrombosis is the most frequent vascular complication of
pancreatitis. It affects mainly the splenic vein because of its proximity to
the pancreas, but the portal and superior mesenteric veins can also be
involved. Thrombus is well visualized on contrast-enhanced images
(Fig. 14).
View larger version (113K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 14. —35-year-old woman with episode of acute pancreatitis and
splenic vein thrombus. Axial enhanced T1-weighted fat-suppressed spoiled
gradient-echo image obtained during venous phase shows low-signal-intensity
thrombus (arrowheads) in splenic vein.
|
|
Conclusion
Although CT is currently the primary imaging technique used to evaluate
patients for acute pancreatitis, recent advances allow MRI to be used for the
diagnosis and detection of complications. MRI has potential advantages because
of its lack of nephrotoxicity from iodinated contrast material and radiation
exposure.
References
- Balthazar EJ. Acute pancreatitis: assessment of severity with
clinical and CT evaluation. Radiology2002; 223:603
–613[Abstract/Free Full Text]
- Naik KS, Ness LM, Bowker AMB, Robinson PJ. Is computed tomography
of the body overused? an audit of 2068 attendances in a large acute hospital.
Br J Radiol1996; 69:126
–131[Abstract/Free Full Text]
- Lecesne R, Taourel P, Bret PM, Atri M, Reinhold C. Acute
pancreatitis: interobserver agreement and correlation of CT and MR
cholangiopancreatography with outcome. Radiology1999; 211:727
–735[Abstract/Free Full Text]
- Morgan DE, Baron TH, Smith JK, Robbin ML, Kenney PJ. Pancreatic
fluid collections prior to intervention: evaluation with MR imaging compared
with CT and US. Radiology1997; 203:773
–778[Abstract/Free Full Text]
- Ward J, Chalmers AG, Guthrie AJ, Larvin M, Robinson PJ. T2-weighted
and dynamic enhanced MRI in acute pancreatitis: comparison with contrast
enhanced CT. Clin Radiol1997; 52:109
–114[Medline]
- Varghese JC, Masterson A, Lee MJ. Value of MR pancreatography in
the evaluation of patients with chronic pancreatitis. Clin
Radiol 2002;57:393
–401[Medline]
- Balthazar EJ, Robinson DL, Megibow AJ, Ranson JHC. Acute
pancreatitis: value of CT in establishing prognosis.
Radiology1990; 174:331
–336[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
A OTO, R ERNST, L GHULMIYYAH, D HUGHES, G SAADE, and G CHALJUB
The role of MR cholangiopancreatography in the evaluation of pregnant patients with acute pancreaticobiliary disease
Br. J. Radiol.,
April 1, 2009;
82(976):
279 - 285.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Introduction
MRI Technique
