Yosef Karo

“ Some disagree regarding the paunch and say that it does contain blood, [6] even post facto the paunch and reticulum of the ruminant stomach is forbidden as any other meat. However the fat that is upon them is as any other meat. Therefore when the rectum and other intestines are salted [7] they are not salted on the inner part over the actual food, (3) rather on the outside where the fat is attached. Rema: If the rectum was salted on the inner side and not on the outer side it is as if it wasn’t salted. [8] if it was cooked this way it is not kosher [9] if it has fat on the outside. ”

“ However one must be careful not to salt it with other meat, put post facto one need not worry. All fat, even of poultry is considered as all other meat for the purposes of salting and washing.
Shach
[1] It seems that the gizzard of poultry is not considered as an intestine for these purposes, for one can simply see that it contains much blood.
[2] The fat of the winding coil contains blood.
[3] Meaning we can assume they do not contain blood, however if they appear blush red they must be salted as any other meat. ”