In our hospital we tend to use CT cholangiography (CTCh) more often than than MR cholangiopancreatography (MRCP) for the non-invasive detection of common bile duct stones because CT is more readily available, and we find CTCh a simpler and more robust test. Of course MRCP has no radiation and does not need any injections, but how do the two tests compare in terms of diagnostic accuracy?
A recent paper addresses this question. 40 patients had both CTCh and MRCP, with the following results:
For detection of choledochal stones the two tests were comparable:
CTCh: sens 87%, spec 96%
MRCP: sens 80%, spec 88%
For detection of gallstones MRCP was a bit better,
CTCh: sens 78%, spec 100%
MRCP: sens 94%, spec 88%
(The reduced sensitivity of CTCh was due to non-opacification of the gall bladder due a stone being stuck in the gall bladder neck)
CTCh demonstrated bile leakage in one patient, and air in the biliary tree in two patients, which were not detected on MRCP.
CTCh also has the advantage over MRCP in demonstrating anastomotic patency, since opacification in CTCh reflects flow, whereas MRCP only demonstrates the presence of fluid.
I've never been able to figure out why are there so few papers on CTCh compared to MRCP. According to the article, Biliscopin (the contrast agent used for CTCh) is not approved for use in the USA. I didn't realise this but perhaps that's part of the reason. (As an aside, it's odd how some substances are permitted in one country but not another, for no obvious reason. Buscopan, for instance, is not licensed for use in the USA either).
Okada M, Fukada J, Toya K, Ito R, Ohashi T, Yorozu A.
The value of drip infusion cholangiography using multidetector-row helical CT in patients with choledocholithiasis.Eur Radiol. 2005 Oct;15(10):2140-5
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