Shunts for portal hypertension: MR and angiography for determination of patency.

Twenty-eight patients with selective and nonselective shunts for portal hypertension were evaluated using magnetic resonance (MR) imaging. Angiographic correlation was obtained in 25 patients. MR imaging enabled the detection of a patent shunt by visualizing the "flow void" phenomenon in 21 patients. Two patients had thrombosed shunts. In these 23 patients, there was no discrepancy between the findings from MR imaging and those from angiography. In the remaining five patients, there was an area of artifact in which no signal was noted, and the shunt could not be evaluated. In all five patients who had this artifact, steel coils were noted in the area of the phenomenon. Thus, MR imaging seems to be an accurate method for detecting shunt patency in all patients with shunts except those who have had prior embolization with steel coils.