Renal dysplasi (RD) is a congenital chronic renal disease affecting young dogs. It is a rather common disease that occurs in a large number of dogs and in some breeds there is a familiar incidence or suspected hereditary background. Both the etiology and pathogenesis are still unknown, but a theory about the cause of RD is that the two components that form the kidney, the uretheric bud and the metanephrogenic blastema, don´t interact normally in the embryo. Kidneys affected by RD contain fetal (immature) structures that are inappropriate for the state of development/age of the dog and abnormal structures caused by an abnormal differentiation. Affected dogs usually are under .