How To Treat Ileus Despite Being Diagnosed With Ischemia?

MY DAD IS 92 RECOVERING FROM ILEUS BROUGHT ON BY STOMACH VIRUS AT HOME DEHYDRATED LED TO HOSPITALIZATION AND CONSEQUENTLY DIAGNOSED WITH MESENTERIC ISCHEMIA HE IS EATING SMALL AMOUNTS BUT WE ARE STILL UNSURE OF SOME TYPES OF FOOD SUCH AS LETTUCE, NUTS, ETC. SUPPOSEDLY, THERE IS NO SPECIFIC DIET SO WE THINK THIS A TRIAL AND ERROR BASIS??