Is kidney volume a factor in determining kidney problems

[concerneddad2017]

My daughter is 1.5 years old. The doctor suspects that she has Beckwith Weidmann syndrome which causes childhood tumors of kidney. so we are getting ultrasounds done for her every 3 months. The latest u/s was in nov 2017. The right kidney volume is 16.44 ml and the left is 31.31 ml. In The august 2017 u/s the right kidney volume was 21.05 ml and left kidney volume was 25.40 ml. Does the volume of kidneys keep changing. What does the reduction in the volume suggest. Please help.