Is it normal for an ultrasound be done immediately after a mammogram if a mass shows up.

Yes.: It is common to followup a mammogram that shows some sort of mass with an ultrasound to further characterize that mass. A fluid-filled cyst, for example, has very different potential than a solid mass, and this is the kind of info you can get from an ultrasound.

It depends: It depends on the workflow of the facility. Some may have immediate interpretations, with the availability of ultrasound before the patient leaves. Others may not be able to accomodate the ultrasound right away, and might have to schedule it for another day.In any case, it is fairly standard to get an ultrasound to evaluate a mass, it is variable as to whether the US can be done immediately.