Swelling in the legs- ERO thing over the norm.

Hello there!

The thing is i was enlisted into the army about 3 months ago. Within 2 weeks my legs started to swell up real son, after doing some daily heavy exercise. It never happened before in civil life. So i let them to do a urine test, and according to it i had some ERO... (can't remember what it was, really) thing over the norm. They said i can't participate in the physical activity anymore. So i stayed in army's hospital for some time, they did EKG, 24h blood pressure, blood test, urine test and so on... everything was OK except urine test, it still showed that ERO thing over the norm. So they decided i should go to the big hospital in nephrology department. I was there 4 days, they did all the same tests including ultrasound. It was fine, the results i mean. My doctor said she think i'm okay, they're not going to do a renal tissue test (as it requires some specific condition in the patient). Oh, i forgot to say the moment i stopped doing physical activity the swelling in my legs was gone overnight.

The thing is i'm home now, haven't done any PHYSICAL activity (like running or sth like that), just walking around... and my legs (or more specifically one leg a little bit more) gets swollen around ankle and shin, the whole leg below thigh. And it's always gone overnight (i take it as if i rest my legs, the swelling goes away). It started to happen in the army after heavy physical actitivy, and it's still here. Why?

Is it kidney related? I've heard if it's kidney related the swelling is all the time, and it's a lot or is painful. Is it? I don't feel any pain with my swelling.

Also, i gained around 15 pounds of mass in the army within 2 months (muscle i guess as i don't seem to have any fat) due to heavy eating and physical activity. Could this be related?

I am 23, around 6'4 ft (193 cm) tall and weigh 180 pounds (82 kg).

Thanks!