what is it

my  15 year old son has just had a renal ultrasound it says a small hypochoic nodule can be seen in the lower pole.what is that.The report also noted that the cyst that has been noted before now measures 7*5*4.8.this seem pretty large to me is it normal for a simple renal cyst to be this big

[Anna Beattie, M.D.]

It is very difficult for me to comment on the ultrasound - it could well be a cyst. I don't know what units the measurements are given in (if in mm then this is quite small and if in cm then not so small), but kidney cysts can indeed get pretty large. There are other more important things to look for on the ultrasound and perhaps you could clarify with whoever arranged the ultrasound whether this was the case and whether they want to do anything else such as follow up or alternative types of imaging (note that only some types of cysts are necessary to follow-up with imaging.)