RADIOLOGICAL DEFINITION OF A NEW MODEL OF PORTAL DIVERSION IN THE RAT

Diversion of portal blood away from the liver can be accomplished in the rat by two straightforward surgical procedures: subcutaneous transposition of the spleen followed later by portal vein ligation. This experiment model has great potential value in the study of liver cell transplants, porto-systemic shunts and hepatic porto-privation. Contrast medium radiology has been used to clarify and define the model further. Splenography, achieved by direct percutaneous puncture, demonstrated the developing spleno-subcutaneous vessels. Collaterals are seen as early as 3 days and appear extensive by 21 days after transposition. Almost all emanate from the convex outer surface of the spleen and course cranially and caudally in the subcutaneous tissues to drain into the subclavian and iliac veins. The appearance of these collaterals correlates well with survival after portal vein occlusion subsequent to splenic transposition. Direct portography demonstrates that, following portal vein ligation, contrast medium is diverted away from the liver into the splenic veins, through and around the spleen, before draining into the systemic circulation through spleno-subcutaneous collaterals. These radiological studies have demonstrated the changed circulatory pathways of this model of portal diversion and have confirmed that it is the splenic veins and the spleno-subcutaneous collaterals which are fundamental to its successful outcome.