A recent u/s showed that I have unilateral hydronephrosis.  When compared to a previous u/s done 7 yrs ago, they noted that it appeared then that I had mild pelviectasis.  Could this be due to improper formation of the ureter even though I did not have symptoms until recently (I am 45 yrs old)?
Hi There are multiple causes of unilateral HY Chat Doctor.  These include blockage by birth(congenital-called PUB obstruction), stones, reflux of urine, cancers of urinary tract etc. I would recommend CT scan of the abdomen without and with contrast, renal function test, urinalysis and possibly might need a genogram and further tests to evaluate the cause. The so-called congenital obstruction can even present itself at 100 years of age for the first time without having any symptoms until that time. Hence, please get evaluated by a urologist.