Question about ketones

I'm not doing the Atkins diet but I have a question that people here
might know the answer to.

A couple of days ago I did a lot of endurance exercise that probably
burned 4,000 kcal. Even though I had a meal high in carbs before I
surely must have burned some fat.

The next day when I urinated I could smell something I can'ŧ really
describe, perhaps a chemical smell. I also smelled this when doing the
Atkins diet. Subsequent trips to the bathroom didn't produce this smell.

I did some Googling and one suggestion was that this could indicate
ketoacidosis because of the presence of ketones.

My thought is, surely endurance exercise which depletes all glucose(?)
would require the production of ketones to burn fat in order to continue
providing energy. So as well as during low carb dieting and diabetic
problems, ketosis should also happen during endurance exercise?

In which case, should I -expect- to smell something weird when I urinate
or should I see the Dr. about this?