We present CORVO (Computing Organoids VOlume in medical images), a tool for calculating the volume of complex time-changing 3D structures from medical videos. In order to identify anisotropies in volume variation over time, CORVO is equipped with a module implementing an advanced regression-based statistical analysis. We tested CORVO for the analysis of the variation of rectal organoids volume, whose anisotropic or missing expansion indicates a pathological state and a non-response to a pharmacological treatment, respectively.