Hi thanks for asking question. As he is having heart problem and one kidney immediately consult him to doctor. He might have acute gastroenteritis .It may be viral or bacterial. Hydration should be maintained.If needed and signs of dehydration severe iv fluid may be given like normal saline infusion. Broad spectrum antibiotic might needed. For vomitting use domperidone If still problem present organic cause must be ruled out by USG like obstruction ... If needed endoscopy done for further work up... Soft and bland diet taken for few days.. Initially start with liquid and semisolid diet. Take care... Dr.Parth Goswami