It is likely that your cousin's wife has a condition called Membranous Nephropathy.
This is an auto-immune condition in which the body's immune system attacks the cells of the kidneys causing them to become thick and release large amounts of protein in the urine. it also causes retention of fluids as well as a lowering of the blood pressure.
The diagnosis is by a kidney biopsy. Blood tests for the levels of antibodies like IgA and IgG are also necessary.
The standard treatment is with steroids to supress the immune response.
To know more, please see:
I hope this helps.
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She needs a kidney biopsy for an accurate diagnosis. I hope her doctors have ordered one.