Do you have any bran cereal to try?
One of the temptations is to use mineral oil but maybe that is not a good idea:
An old fashioned remedy has been the oral administration of mineral oil. It is best to avoid this temptation as mineral oil, being a light fluid without flavor, is easily inhaled accidentally into the respiratory tract. Since it is a mineral based compound, it cannot ever be removed by the body and the immune system will forever attempt to wall it off with inflammatory granulomas.
http://www.marvistavet.com/html/body...megacolon.html