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MRCP and Static Fluid Imaging with MRI
The high signal intensities of fluid obtained in heavily T2 weighted MR images of the abdomen allow for a variety of applications. Applications include imaging of the bile and pancreatic ducts (MR cholangiopancreatography, MRCP), imaging of the kidneys, ureters and bladder (MR-IVP, or MR-urogram), and MR fistulography.
MRCP
There are many common conditions that require imaging of the bile and pancreatic ducts. Common bile ducts stones (migrated from the gallbladder) can cause recurrent pain before or after cholecystectomy (removal of the gallbladder). Tumors of the bile duct and pancreas often require defining the anatomy of these ducts.
The best method to image the pancreatic ducts and bile ducts is with ERCP. In this well accepted procedure, an endoscope is advanced from the mouth into the small intestine where the bile and pancreatic ducts empty. The ducts are entered with a small catheter (cannula) through which dye is injected. The advantage of ERCP is the ability to perform treatment at the same time as diagnosis. ERCP allows for stone extraction, sphincterotomy, or stent placement. Thus, ERCP is a robust tool in both the diagnosis and treatment of pancreatic and biliary disease.
There are situations when MRCP can be used to gain similar images to ERCP, without performing the invasive ERCP procedure. Some of these situations can be summarized as follows:
- To rule in or out common bile duct stones. MRCP attempts to reduce false negative ERCP rate and gain same information without performing an invasive procedure. Some believe MRCP is best for patients with low or moderate stone risk (See references below). Particular value in post cholecystectomy pain syndromes.
- Failed cannulation at ERCP due to post surgical anatomy, scarred ampulla
- Pre-operative planning for laparoscopic cholecystectomy or liver transplantation. Evaluate aberrant ductal anatomy
- Evaluate for pancreatic divisum in recurrent pancreatitis. Secretin stimulation may be best.
- Additional information in the diagnosis of pancreatic tumors
- Additional information in complex acquired and congenital biliary abnormalities: choledochal cysts, Caroli’s disease, sclerosing cholangitis, HIV cholangitis, etc.
- Better sensitivity than ERCP for intrahepatic stones (e.g. Oriental cholangiohepatitis).
The examples below illustrate typical cases:
References
Calvo MM, et al. Role of magnetic resonance cholangiopancreatography in patients with suspected choledocholithiasis. Mayo Clin Proc, 2002, 77(5):407-12 • View Abstract
Taylor AC, et al. Prospective assessment of magnetic resonance cholangiopancreatography for noninvasive imaging of the biliary tree. Gastrointest Endosc.2002 Jan;55(1):17-22• View Abstract
Fulcher AS, et al. MR Cholangiopancreatography: Technical advances and clinical applications. Radiographics, 1999, 19: (25-41).
Reinhold C, et al. Choledocholithiasis: Evaluation of mrcp for diagnosis. Radiology 1998; 209: 435-440.
MR-IVP
CT scanning, intravenous urogram (IVP, IVU) and ultrasound provide the means to diagnose urinary obstruction due to stones or tumors in the vast majority of circumstances. When renal function does not permit the use of intravenous contrast, then MR-IVP can provide an alternative wat to image the renal collecting structures, ureters and bladder.
In the case below, an injury to the ureter caused obstruction of the ureter in the pelvis. The MR-IVP clearly demonstrates the level of the obstruction and an adjacent urinoma (fluid collection containing urine).
MR Fistulography
The surgical approach to peri-rectal and peri-anal fistula may vary depending on the site of origin of the fistula, it’s extent, and it’s relationship to the anal sphincter. MR Fistulography allows exquisite delineation of these relationships and classification of the type of fistula.
MR can correctly classify the type and extent of fistula based on criteria based on the Parks Classification, guiding appropriate management. An excellent review can be found in this abstract.
Additional value to the surgeon can be achieved by the MRI demonstration of secondary extensions of the fistula, detection of supralevator abcess and horseshoe fistulae. This may be of particular value for patients with Crohn disease or recurrent fistula. This is discussed in another useful abstract.
The following example is typical:
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