We present an evaluation of the local field corrections to the pion optical potential in nuclear matter. These corrections, which amount to including an infinite subset of rescattering terms in the π-nucleus optical potential, are shown to give an improved description of the coupling of the nuclear ground state to the 1p−1h, 2p−2h, …, np−nh excited states. Furthermore it is shown that, if in the evaluation of these local field corrections, the nucleon pole in the p₁₁ channel is correctly taken into account, one obtains a realistic description of true pion absorption processes with one, two or more nucleons knocked out. Numerical estimations of these corrections, incorporating the nucleon's Fermi motion, recoil corrections and correlations effects are presented. Their density, energy and momentum dependence is studied and the influence of different factors (correlation, π-nucleon range, recoil corrections) is investigated. Finally, these theoretical predictions are compared to the phenomenological values obtained by a fit to the experimental data.