We hypothesized, therefore, that the preoperative dIVCmax/IVCCI ratio (maximum diameter of inferior vena cava-IVC- at the expiration = dIVCmax and the collapsibility index of the IVC =IVCCI) could greater foresee the incidence of hypotension after spinal anesthesia than the established IVCCI measurements. In light of this hypothesis, we prospectively examined both the dIVCmax/IVCCI ratio and IVCCI before spinal anesthesia in a population who fulfilled predetermined inclusion criteria and we set out to evaluate the diagnostic performance of this indices in predicting spinal-induced hypotension.