My 12 year old daughter (5 foot 2 inches - 125 lbs - funtional heart murmur) woke up with a high fever October 23. Doctor said next day it was a virus. Laster in week sore throat doctor prescribed zithermax, and enlarged spleen. Bloodwork came back negative for mono. Spleen is still enlarged. yesterday morning she had an xray and ultrasound. We were told if problem we would get call yesterday afternoon. Would it be ok to give her milk thistle to reduce spleen. My daughter is very active and is restricted from sports. She really wants to get back in the pool and soccer field. How long does it take for spleen to shrink?