Prepared by Maria E. Pace, MD, CT/MR Fellow, and Barry Daly,
MD, FRCR, Associate Professor, Department of Radiology,
University of Maryland, Baltimore, MD.
A 63-year-old female presented with epigastric abdominal pain.
Laboratory values demonstrated an amylase of 67, lipase of 2630,
and elevated liver function tests. An image from a coronal
reformatted single breath-hold magnetic resonance
cholangiopancreatogram (MRCP) is shown (figure 1). What is the most
The noninvasive radiologic evaluation of biliary tract
obstruction has, until recently, been primarily evaluated by CT or
ultrasound. While these modalities are useful for determining the
presence of obstruction, direct cholangiography or ERCP remains the
gold standard, having the highest sensitivity for visualizing
biliary tract anatomy and for determining the level of obstruction.
However, ERCP is an expensive, invasive procedure which is operator
dependent and can be associated with major complications.
MRCP provides a safe, noninvasive alternative to ERCP which can
be performed as an out-patient procedure, usually without sedation.
MRCP images are rapidly obtained utilizing a heavily T2-weighted
sequence which relies on the inherent brightness of fluid to
delineate biliary anatomy. Cholangiogram-like images can be
obtained by acquiring signal from a single thick slab through the
upper abdomen using a prolonged echo time to suppress solid
background tissues. Oral contrast agents can also be administered
to suppress adjacent bowel signal. In this patient, the slab of
data for figure 1 was acquired in a 2-second breath-hold utilizing
an EXPRESS fast-spin echo sequence on a 1.5-Tesla MR scanner. This
technique virtually eliminates any motion misregistration, as well
as increases signal-to-noise ratio and improves spatial resolution.
Software that can provide a single-shot acquisition is available on
some MR systems. Such techniques include the single-shot fast-spin
echo (SSFSE) sequence and its counterpart, half-Fourier single-shot
turbo-spin echo (HASTE) acquisition.
The role of MRCP is broad. It can be used as a primary
diagnostic cholangiography and pancreatography study. In cases of
failed or incomplete ERCP, MRCP can be used to delineate biliary
tree anatomy, both proximal and distal to the level of obstruction.
Additionally, MRCP can be used in conjunction with T2-weighted and
gadolinium-enhanced gradient dynamic, or fat-saturated SE
T1-weighted sequences of the liver and pancreas to determine the
cause of obstruction, as well as to identify the extent of local
and metastatic liver spread in the setting of malignant
obstruction. MRCP allows the determination of patients who need
biliary drainage and the selection of the most appropriate
route--either via ERCP or percutaneous intervention. Fulcher et al
demonstrated an accuracy of 98.2% for the diagnosis of malignant
obstruction utilizing MRCP. In that study, use of MRCP obviated the
need for ERCP by excluding biliary stones in 95 of 300 patients
(32%) with undiagnosed abdominal pain or acute pancreatitis.
Recent studies of the MRCP diagnosis of choledocholithiasis are
favorable, with sensitivity ranging from 81 to 100% and specificity
ranging from 97 to 100% for the detection of biliary stones.
Biliary stones appear black on the background of bright/white bile.
This is compared to ERCP data, published by Frey et al, which
report a sensitivity of 90.4% and a specificity of 98% in the
detection of choledocholithiasis.
MRCP also can be used to assess variant and postoperative
biliary anatomy, acute or chronic pancreatitis, and
The disadvantages of MRCP compared to ERCP include the inability
to biopsy tissues, the inability to perform a therapeutic role
(such as stent placement or endoscopic sphincterotomy), and
slightly diminished image resolution.
Overall, the role of MRCP is increasing as a reliable and
sensitive exam that can perform a rapid acquisition, yielding
diagnostic information comparable to that of ERCP.