Polymer treatments reduce adhesion of comminuted stone in rat bladder

A method for inhibiting the adhesion of stone fragments in comminution is presented. Surfaces are coated with a molecular layer of so-called "excluding" polymer. In experimental tests, rat bladders were injected with comminuted urinary stone (phosphate or oxalate) in saline which contained small amounts of excluding polymer (0.1% hyaluronic acid or polyvinyl pyrrholidone). The urinary tract was then irrigated with fresh polymer solution and examined for residual stone. A ten-fold reduction in particle count was obtained, compared with irrigation with normal saline. The possible applications in percutaneous and extracorporeal lithotripsy are discussed. It seems that the "coagulum" and "exclusion" types of polymer irrigant might find complementary uses: the former for manual extraction of coarse particles and the latter for flushing out after fine comminution.