  Using the fluctuation exchange approximation and a three-orbital model, we
study the band renormalization, Fermi surface reconstruction and the
superconducting pairing symmetry in the newly-discovered iron-based
superconductors. We find that the inter-orbital spin fluctuations lead to the
strong anisotropic band renormalization and the renormalization is orbital
dependent. As a result, the topology of Fermi surface displays distinct
variation with doping from the electron type to the hole type, which is
consistent with the recent experiments. This shows that the Coulomb
interactions will have a strong effect on the band renormalization and the
topology of the electron Fermi pocket. In addition, the pairing state mediated
by the inter-orbital spin fluctuation is of an extended s-wave symmetry.
