How long can bulimia go undetected by family?

Bulimia: This is a very subjective question. I think that it depends on the individual and the family.

Possibly forever: Symptoms that suggest bulimia would include: rapid exit to the bathroom after ingesting meals, dental repairs like enamel erosion, vacillating weight, preoccupation with food, calories, weight, fat phobia, diet pill or laxative usage, etc.