This excerpt from an EEOC (Equal Employment Opportunity Commission) publication says it all. My take is that you don't have a disability (I have an ostomy and do not consider myself to have a disability). However, even if it was considered a disability, you would be covered by the ADA. Since I presume you do not need any accommodation, it is really a non-issue and I would not disclose it.
Per the EEOC - "If you have a disability and are qualified to do a job, the ADA protects you from job discrimination on the basis of your disability. Under the ADA, you have a disability if you have a physical or mental impairment that substantially limits a major life activity. The ADA also protects you if you have a history of such a disability, or if an employer believes that you have such a disability, even if you don't.
To be protected under the ADA, you must have, have a record of, or be regarded as having a substantial, as opposed to a minor, impairment. A substantial impairment is one that significantly limits or restricts a major life activity such as hearing, seeing, speaking, walking, breathing, performing manual tasks, caring for oneself, learning or working."