Application Process for Medical Certification
Applicant History - Item 18. Medical History
i. Stomach, liver, or intestinal trouble
The applicant should provide history and treatment, pertinent medical records, current status report, and medication. If a surgical procedure was done, the applicant must provide operative and pathology reports.

It requires review, but unless serious side-effects (dumping syndrome or hypoglycemia would tend to be the most troublesome from an aeromedical perspective) after surgery, approval tends to be almost routine.