The first concern with FOLFIRI diarrhea is to stop it, immediately followed by re-hydration. They have a number of tricks up their sleeves to stop the diarrhea which with irinotecan can be "early" or "late" I had it continuously, the entire cycle, and was admitted and admitted for hydration. They'll worry much less that he's not eating, but ultimately could give him TPN if he really can't eat anything for a long period of time. The not eating isn't an emergency though, severe diarrhea/dehydration is. My onc told me that I would never be able to keep up orally with the fluid loss I had through the constant diarrhea. You were very wise to go to the hospital. If he is dehydrated enough it could cause a fever.
I hope they find a near instant cure for all that is ailing him.
58 yo Type1 DM 48 years
12/09 Stage IV 2/22 nodes + liver met, colon resec
3 tx FOLFIRI, liver resec 4/10
9/10 6 mos off chemo, Neg PET&CTC CEA nl
2/11 finished total 10 rounds chemo
9/13 ^17th clean PET/CT NED for now