has anyone had this happen 3 wks post op?

my daughter is 3 weeks post - op --- doing fantastic with approx 30 lbs weight loss. Meanwhile, she developed this left flank pain - she describes the same pain as just after surgery. Anyone ever have this experience? How long did it last? Is it muscle pain? pinching from a suture? Mommy W. is supportive that it will pass, however, it's difficul****ching her discomfort.... thanks in advance....