<p>Sasuke was healed using Hashi Cells by Kabuto...Probably transplanted em to heal his organs etc...and also, just before, Hashirama himself passed on his chakra and a jutsu to seal Sage Chakra to Sasuke, which is why Sasuke went after Madara, remember?
</p><p>Probably because of those two things, he was able to awaken One-Eyed Rinnegan,...along with the Sage of 6 Path's boost of help, when receiving the Six Paths Shadow Style.
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