cuando dicen habló sin empacho significa que hablo sin pena, sin reservas
tambien indigestion, como escribieron los colegas.

I don't much care for this as a substitute for "empacho," but in a medical context it's probably your best bet. "Empacho" is slang, so a more accurate translation would be "bellyache." Indigestion is what my medical dictionary says, but empacho (at least where I live) is the pain or discomfort you feel when your stomach is bloated (from overeating, as in indigestion, but also from things like appendicitis).

The traditional cure for empacho, by the way, is a tablespoon of oil taken internally or rubbed on the tummy, or both if it's really bad!