Hello and welcome to HCM.
As an 
Urologist,  i must define the medical term 
proteinuria means,  excessive leak of protein in the urine,  above normal limit of 150mg / day.
In urine routine test, he may have found, excess level of 
albumin, which is a form of protein. Typically, the next test to accurately assess protein loss in urine, is to check  24 hour urine protein.
With an 
ultrasound scan of the abdomen, and blood urea, and 
creatinine test, one can get a good idea,  of source of protein loss. You're welcome to send a copy of reports here,  in my name,  to get an expert opinion.