Recently we were given the opportunity to partner with AVIM in Annapolis to image an eight-year-old, 8.6 kg. fawn pug. The animal presented with a complex history of elevated liver values, an elevated bile acid panel, a mildly decreased liver size, diabetes mellitus, and hypothyroidism. We were asked to image the patient’s portal venous system to evaluate for any underlying hepatopathy including the possibility of an anomalous shunt in the portal system.
Utilizing multiple high resolution imaging sequences, including 2D and 3D TOF (Time of Flight imaging), we have been successful in visualizing the portal venous system in large and small breed animals. TOF utilizes the movement of fluid within a vessel to evaluate the vasculature of a subject while suppressing the signal from the surrounding tissues. Shown here are several Maximum Intensity Pixel (MIP) reconstructed images from the TOF sequences that were performed.
In this case we were able to identify the following: “There is a dramatic change in the diameter and course of the portal vein at the level of T11‑T12 which shows an anomalous vessel coursing toward midline and then dorsally with enlargement of the azygos vein cranial to this region. Although the MIP images give the impression of a portacaval shunt based on the gross dilation of the azygos vein, it is assumed that this is a portal azygos shunt which is incompletely imaged due to the direction of flow and curvature of the aberrant shunt vascularity relative to acquisition parameters... The MIP reconstructions...show the abnormal portal vein termination immediately adjacent to the generation of enlarged azygos dorsal to the normal coursing caudal vena cava.” Many thanks to Dr. Russell Tucker for his clinical interpretation of these images.
Utilizing these imaging techniques, we are able to evaluate and diagnose a multitude of vascular abnormalities including aneurysm, stenosis, atherosclerosis, blood clots, and renal hypertension—all without the use of ionizing radiation or the absolute necessity for invasive procedures or contrast injections. Magnetic Resonance Venography and Angiography continue to improve our ability to care for and treat our furry friends by providing us with exceptional intel in the fight against vascular disease.
Figure A (left): 2D TOF MIP (maximum intensity pixel) sagittal reconstruction demonstrating abrupt truncation of the portal vein (PV) and sudden enlargement of the azygos vein (AV) dorsal to the caudal vena cava (CVC). The portal-azygos shunt can be only partially outlined in this single reconstruction plane composite image due the tortuous pathway of the shunt. Cranial is to the left and caudal is to the right. Dorsal is to the top and ventral is towards the bottom of image.