  In this work the quantum gravitational equations are derived by using the
quantum hydrodynamic description. The outputs of the work show that the quantum
dynamics of the mass distribution inside a black hole can hinder its formation
if the mass is smaller than the Planck's one. The quantum-gravitational
equations of motion show that the quantum potential generates a repulsive force
that opposes itself to the gravitational collapse. The eigenstates in a central
symmetric black hole realize themselves when the repulsive force of the quantum
potential becomes equal to the gravitational one. The work shows that, in the
case of maximum collapse, the mass of the black hole is concentrated inside a
sphere whose radius is two times the Compton length of the black hole. The mass
minimum is determined requiring that the gravitational radius is bigger than or
at least equal to the radius of the state of maximum collapse.
