Contrast-enhanced Magnetic Resonance Angiography for Diagnosis of Portosystemic Shunts in 10 Dogs

Computed tomography angiography, sonography, scintigraphy, and portography can be used to evaluate the portal vasculature to evaluate for a portosystemic shunt (PSS). Time-of-flight magnetic resonance angiography (TOF-MRA) and contrast-enhanced MRA (CE-MRA) are other potentially useful techniques. The aim of this study was to evaluate CE-MRA in 10 dogs suspected of having a PSS. Noncontrast MR images of the abdomen were obtained using a Siemens Symphony MR-scanner (1.5 T) and a T1-weighted FLASH-3D sequence with a very short scan time (about 20 s). After injection of contrast medium, the initial sequence was repeated five times. The sequence with the best contrast medium filling of the portal vasculature was selected subjectively, subtracted from the initial survey image series, and a maximum intensity projection (MIP) of the subtraction data, in multiple views, was created. The cross-sectional and MIP images were evaluated for abnormal portosystemic vasculature. A single PSS was identified and confirmed at surgery in all dogs. A portocaval shunt was found in five dogs, a portophrenic shunt in three dogs, a portoazygos shunt in one, and a central divisional intrahepatic shunt in one other dog. Based on our results, CE-MRA is a useful tool for imaging abdominal and portal vasculature and for the diagnosis of a PSS.