K52.1 (toxic gastroenteritis (drug induced gastroenteritis)) has a code first note stating, "code first T51-T65 to identify the toxic agent and a use additional code for adverse effect, if applicable". We are wondering if we can use this code for chemotherapy induced diarrhea. If yes, none of the T51-T65 codes apply. Can we just bill this using K52.1 and T45.1X5A? We just were not sure what to do with the code first instruction since none of those codes apply. If they don't apply, do we go to the K52.9 - noninfective gastroenteritis, unspecified? Any advice about the code first instruction would be appreciated.