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Figure
1 |
History:
45 year old female with history of biliary colic. Ultrasound showed
gallstones and possible common bile duct stone. The patient was
referred to Main Street Radiology for an MRCP - MR
cholangiopacreatography.
Findings:
3D MRCP image (figure 1) demonstrates multiple gallstones as well as
multiple common bile duct stones.
Discussion:
Ultrasound is highly sensitive for the diagnosis of bile duct
dilatation, but insensitive for detection of common bile duct stones,
with sensitivities reported to be as low as 20%. In pre-operative
cholecystectomy patients, presence of bile duct dilatation on
ultrasound or abnormal liver function tests was associated with 98%
sensitivity for choledocholithiasis but only 34% specificity
(Radiology 2001; 220:677-682), potentially leading to unnecessary ERCP
or intra-operative cholangiograms. Other studies have concluded that
up to 25% of acute cholecystitis patients have choledocholithiasis,
and as many as 15% of theses cases were unsuspected pre-operatively.
MRCP has become a powerful non-invasive
tool in the diagnosis of common bile duct stones. Numerous published
studies report sensitivity and specificity between 80% and 100%. MRCP
should be considered in the preo-operative work-up for cholecystectomy,
especially in patients with clinical or ultrasound findings suggestive
of choledocholithiasis.
Indications for the performance of MRCP
are growing. Currently, MRCP is performed most frequently to exclude
common bile duct stones, primary sclerosing cholangitis and congenital
bile or pancreatic ductal anomalies. MRCP is equally effective at
diagnosing choledocholithiasis pre-operatively, as well as following
cholecystectomy.
High quality MRCP images are generated
using "single-shot-fast-spin-echo" technology, where
three-dimensional images of bile and pancreatic ducts can be obtained
in less than 2 seconds, without prior administration of intravenous or
oral contrast. This technology is only available on high field magnets
with advanced software.
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