The invention presents is a fluid isolation system and method for confining fluid is a biological mass having at least one upstream channel and downstream channel. The system includes a delivery conduit for administering fluid to the biological mass and a collection conduit having and external seal and for retrieving the fluid. In the use of the system, the delivery conduit is positioned adjacent to or into the upstream channel and the collection conduit is inserted adjacent to or into the downstream channel. In one manner to confine the fluid, the seal on the collection catheter is activated to occlude outside fluid flow and divert the fluid into the lumen of the catheter.