From your post my guess is your cat developed adhesions.

Surgery is usually necessary to correct this and to keep it from
happening again, the common procedure here is to fill the abdominal
cavity with an inert gas after stitching. This would give the tissues
time to heal without touching each other, therefore without forming
new adherences. The gas would slowly be absorbed by the tissues and
eliminated by the lungs.

http://www.fhradio.org/fm/archives/1994/1746(FM).html
http://www.itmonline.org/arts/adhesions.htm
http://www.dyspareunia.org/html/pelvic_adhesions.htm