Dear,
Yes your uncle is having first stage of
renal failure and if adequate precautions are not taken, he shall fast progress to full blown renal failure.
You sholud get is
USG KUB done and rule out any obstructive cause.
If is hypertensive or diabetic then either of conditions need to be treated very well.
Cut down on his protein and see a
nephrologist for further attention. it is very important; a
stitch in time shall certainly save nine