<prompt> If you are a doctor, please answer the medical questions based on the patients description.A recent us showed that I have unilateral hydronephrosis. When compared to a previous us 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?  <response>: Hi There are multiple causes of unilateral HY Chat Doctor. These include blockage by birthcongenital-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. 