Unfortunately, we cannot tell you what your mother's kidney prognosis could be. It would depend upon the levels of protein found in her urine. When the doctor sends a urine sample for examination he/she is looking for blood in the urine, protein in the urine, and under the microscope specific types of cells and other material that could indicate damage to the kidneys. Doctors will generally run a blood test called the serum creatinine. This test measures kidney function and if it is elevated above normal levels, it could indicate kidney dysfunction from lupus nephritis.
There are 6 classes of lupus nephritis. Class I is almost never seen because it shows minimal changes and doesn't have any clinical signs. The Classes that come to clinical attention are Class 3, 4, and 5. Class 3 and class 4 are called proliferative lupus nephritis and are very inflammatory and can develop renal insufficiency fairly quickly. The difference between Class 3 and Class 4 is the percent glomerular involvement. Class 5 Lupus nephritis is also called membranous lupus nephritis. In this particular Class the immune complexes are made in lupus deposit on the urine side of the glomerular basement membrane. The glomeruli are the filtering units of the kidney, and as blood is filtered to form the initial urine, it is filtered across the glomerular basement membrane. In Class 5 the immune complexes are on the urine side of the glomerular basement membrane and they make the basement membrane leaky for protein. Class 5 lupus nephritis is characterized by a large amount of protein in the urine. Unlike class 3 and 4 there is not a lot of inflammation in the kidneys. Therefore Class 5 tends to be less aggressive, does not usually present with kidney failure or abnormal kidney function, but can progress to towards kidney insufficiency over a long time if not controlled.
I hope that this information was helpful, I realize that it does not answer all of your questions and I apologize for that. I wish you and your mother the very best.
Peace and Blessings
Look For The Good and Praise It!