  We reexamine the boundary conditions of spin diffusion equations for dirty
semiconductor heterostructures with weak linear Rashba spin-orbit interaction.
Doing so, we focus on the influence of tangent derivatives of the particle
density at the boundary on the magnetization. Such derivatives are associated
with a spin accumulation in the presence of a density gradient. We show that
the tangent derivatives enter the boundary conditions and argue that the
spin-Hall effect is absent in such systems because of this fact.
