A rudimentary disc is an underdeveloped disc, in this case located between S1 and S2. I'm not sure what it means in this regard, without knowing what else the MRI reveals. The sacral discs are mostly fused together so there usually aren't disc problems at the sacral level.
What are your symptoms and what else does the MRI say?
thanks for replying.this is on my mri. l3-4 there is borderlinecanal stenosis , lateral spondylotic changes contribute to moderate bilateral neural foraminal narrowing at l3-4 and l4-5 and mild-moderate bilateral neural foraminal at l5-s1, protrusions at t5-6 and t11-12, schmorl's nodes at t8-9,t9-10,t10-11 and t12-l1