Final answer:
The code 558.1 corresponds to Crohn's disease of the small intestine. I-9 to I-10 GEMs file is used to map codes from ICD-9-CM to ICD-10-CM.
Step-by-step explanation:
The code 558.1 corresponds to the medical condition called inflammatory bowel disease (IBD), specifically Crohn's disease of the small intestine. It is classified under the ICD-9-CM code system. However, ICD-10-CM introduced a new code system, and the corresponding code for 558.1 is K50.11. The I-9 to I-10 GEMs file is a tool used to map codes from the old ICD-9-CM system to the new ICD-10-CM system.