Severe nausea (not pain) in mid and upper abdomen

My father had severe nausea about a month ago which lasted for about 3-4 days.  It was bad enough to warrent a trip to the ER. A day later he was back in the ER and then spent 1 night in the hospital. His nausea was accompanied by vomiting multiple times as well as being extremely cold and shivering badly but also sweating.  They did tests and could find nothing other than something in his blood that had a high count, which lead them to believe it was a digestive virus.
Just 4 days ago he had surgery for a broken leg.  Today he started having the same nausea-like symptoms that he did a month ago.  These symptoms seem to occur after bowel movements.  In the last 6 months he has complained of 'minor' nausea after bowel movements with NO vomiting.
I have done some research and found symptoms similar in a condition known as cyclic vomiting syndrome (CVS).  I am looking for some more information or suggestions because the doctors don't seem to have an answer for us.
Thank you and Merry Christmas!