Nephrotic level proteinuria usually requires renal biopsy to establish the cause, unless this is immediately evident.
In some cases the protein leak may be large enough to cause nephrotic syndrome.
Renal vein thrombosis is more common in patients with nephrotic syndrome, although studies have shown high variability among these patients, with rates of 5 to 62 percent reported.
Nephrotic syndrome is marked by abnormally low levels of albumin (hypoalbuminemia), abnormally high levels of cholesterol in the blood (hypercholesterolemia), and fluid retention (edema).
Minimal change disease is a form of nephrotic syndrome seen in children, characterized by swelling and weight (from fluid retention), foamy urine, and loss of appetite.