The invention provides methods for treating an obstructed biological conduit that include administering to the conduit an agent that can degrade extracellular matrix of obstructing tissue. Particular methods include delivery of an enzyme or a mixture of several enzymes to the area or region of obstruction wherein the enzyme(s) have the capability to degrade extracellular matrix components within the obstruction thereby restoring the normal flow of transported fluid through the conduit. The invention also includes prophylactically dilating a section of conduit to minimize the risk of obstruction formation. The invention further includes methods for prolonging patency of hemodialysis access.