'Sons of Anarchy' Creator Rushed To Hospital ... Bum Appendix

The genius behind "Sons of Anarchy" was rushed off set and into an L.A. hospital where he lost some weight -- in the form of an appendix -- and then Instagrammed the gruesome photos.

TMZ has confirmed ... Kurt Sutter went under the knife Monday morning after experiencing serious pain on the set of the hit FX show.

We're told Sutter is resting comfortably. It doesn't appear it will impact shooting.