  The elastic constants of a discotic lyotropic nematic liquid crystal are
calculated by means of a pseudo-molecular approach as functions of the micellar
shape anisotropy. By assuming that the temperature dependence of the ratio of
the elastic constants comes from the temperature dependence of the micellar
shape anisotropy, the theoretical predictions are connected with experimental
measurements for the ratio $K_{33}/K_{11}$. This procedure permits to
determine, in a phenomenological way, the temperature dependence for the ratio
of elastic constants and for the micellar shape anisotropy near the
nematic-isotropic transition in agreement with the experimental data.
