What is the investigation shown above?
What is the diagnosis shown on this investigation?
Name at least 3 advantages of this investigation over ERCP
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(See below for further details)

From: G Mackay, D Murphy, G Dewar


Magnetic resonance cholangiopancreatography (MRCP) was first reported in 1991 by Wallner. Since then it has become a well recognised investigation in the non-invasive work-up of patients with pancreaticobiliary disease including calculus disease, chronic pancreatitis, biliary strictures, sclerosing cholangitis and congenital disorders. It is particularly useful in preoperative mapping of the ductal systems or where previous surgery may have altered the anatomy e.g. laparoscopic cholecystectomy.

MRCP is made possible by stationary fluid in the ducts producing a high intensity signal. This can then be recognised separately from the surrounding structures. Once the area in question has been defined a series of thin slices 2 - 5mm thick are taken and computer processing is applied to construct the images. The images can be either cross-sectional (tomographic), to visualise the bile ducts as well as surrounding structures or projectional (cholangiographic) which produces images similar to a cholangiogram. A contrast can be used to produce finer detail of the smaller ducts but this is not routine. Furthermore an MR examination of the liver and pancreas can be incorporated into the examination but again this is not routine and it adds a considerable amount of time onto what is otherwise a very quick examination.

There are many advantages of MRCP compared with previous imaging techniques. It does not require the use of contrast so avoiding the possibility of a reaction. In fact safety is comparable to ultrasound providing the few contraindications are observed and since no radiation is used. No special patient preparation is required and the procedure is very rapid to perform.

When compared to ERCP or PTC the accuracy is very similar. MRCP has a sensitivity and specificity of 91% and 98% respectively for choledocholithiasis (1,2,3). Its accuracy for benign and malignant obstruction is 90%. Furthermore it does not carry the 5 - 30% failure rate associated with ERCP (4). It is also spares the morbidity (1-7%) and mortality (0.2-1%) of ERCP (4,5) and is twice as cost effective (5).

The disadvantage is that it is solely a diagnostic test. For this reason it should not be used in choledocholithiasis when there is a high likelihood of a CBD stone. In this situation ERCP would be indicated since endobiliary therapy can also be carried out. MRCP is not the initial investigation of choice in cholecystitis as ultrasound is just as accurate and much more cost effective.

MRCP has many benefits when compared to other methods of biliary imaging and will be used increasingly as MR technology becomes more available.


References:

1. Reinhold C, Tacunel P, Bret P M et al
Choledocholithiasis: evaluation of MR cholangiography for diagnosis
Radiology 1998; 209: 435-42
2. Soto J A, Alvarez O et al
Diagnosing bile duct stones: comparison of unenhanced helical CT, oral contrast-enhanced CT, cholangiography and MRCP.
AJR 2000; 175: 1127-34
3. Varghese J C, Liddell R P et al
Diagnostic accuracy of MRCP and US compared with direct cholangiography in the detection of choledocholithiasis.
Clin Radiol 2000; 55: 25-35
4. Schutz S M, Abbott R M.
Grading ERCPs by degree of difficulty
Gastrointest Endosc 2000; 51: 535-9
5. Lembert M E, Betts C D, Hill J et al
Endoscopic sphincterotomy: the whole truth
Br J Surg 1991; 78: 473-6