OMAHA — Kathleen Baker stared at the seemingly simple question on the form distributed to members of the United States Olympic swim team. What challenges did she have to overcome on her way to qualifying for the Rio de Janeiro Games?

For Baker, one of about 700,000 Americans who have Crohn’s disease, the answer could fill a 70-page spiral notebook, and it is not as easy as WebMD. How does one begin to explain the physical and psychosocial challenges of living with a disease — a chronic, recalcitrant gastrointestinal inflammation — that can be embarrassing to talk about? How could she describe the medications that can lose their efficacy over time, or a fatigue so fathomless it can sap your will?

Baker, 19, has fought to prevent her health challenges from defining her. Talking for the first time about her condition, she said: “I found doctors who weren’t going to be just like, ‘You’re Kathleen with Crohn’s disease.’ I need to be Kathleen the swimmer with Crohn’s disease.”

Baker, who qualified for the Olympics in the backstroke — and perhaps a relay — seven years after receiving the life-altering diagnosis, will not be the first American Olympian with Crohn’s. The kayaker Carrie Johnson, now retired, made the first of three Olympic teams in 2004, a year after she was found to have the disease. Other prominent athletes who have the condition include the N.F.L. quarterback David Garrard, who had a foot of his intestines removed, and the former N.H.L. player Kevin Dineen, who played 16 seasons after learning he had Crohn’s.