The software first tries to identify the sacrum; if that detection is uncertain, it validates the labels against three anatomical “anchors”: costal facets expected at T12, the conus medullaris ending at L1, and the aortic bifurcation at L4–L5. When at least two anchors agree with the current labels, the L5–S1 assignment is deemed correct; otherwise the entire stack is shifted up or down by one level. If confidence is still low and two or more anchors disagree, CoLumbo also checks whether the last axial slices truly correspond to L5–S1 and adjusts accordingly.