Hello, We Are Trying To Find Out Why My Husband

Hello, we are trying to find out why my Husband keeps having these episodes with his stomach periodically of watery diarrhea cramping and sometimes nausea? He has already had a colonoscopy an endoscopy several ultra sounds blood work and tested his gall bladder, nothing has been found......his Mom also had similar problems, he said she had some kind of colitis and also had her gall bladder removed......please help, we have been to a gastroenterologist several times..... We have run out of options