Healthy kidneys keep protein in the blood. When the kidney filters, called glomeruli, are damaged, protein leaks into the urine. This is called proteinuria, or albuminuria when the protein is albumin. It is one of the earliest signs of kidney damage and a strong predictor of whether kidney disease will get worse.
Causes
- Diabetes and high blood pressure, the most common causes
- Glomerulonephritis, inflammation of the kidney filters. Examples include IgA nephropathy, lupus nephritis, membranous nephropathy, focal segmental glomerulosclerosis (FSGS), and minimal change disease.
- Infections and some medicines
- Temporary causes such as fever, intense exercise, or dehydration, which is why an abnormal test is usually repeated
Symptoms
Small amounts of protein cause no symptoms. Larger amounts can cause foamy urine and swelling in the face, belly, legs, or feet. Some types of glomerulonephritis also cause blood in the urine, which may look pink or cola-colored, and high blood pressure.
Nephrotic syndrome
Nephrotic syndrome happens when a large amount of protein is lost in the urine. It causes low protein in the blood, significant swelling, high cholesterol, and a higher risk of blood clots and infections. It needs prompt evaluation by a kidney specialist.
Tests
- Urine albumin-to-creatinine ratio (UACR) or urine protein-to-creatinine ratio (UPCR) to measure how much protein is in the urine
- Urinalysis to look for blood and other clues
- Blood tests for kidney function and, in some cases, immune system and infection markers
- Kidney biopsy, a small tissue sample, which is often needed to find the exact type of glomerular disease and choose the best treatment
Treatment
- Controlling blood pressure, often with medicines that also lower protein in the urine
- Other kidney-protective medicines when appropriate
- Treating the underlying cause, which for some types of glomerulonephritis includes medicines that calm the immune system
- Lowering sodium in your diet and using water pills (diuretics) for swelling
- Managing cholesterol and preventing blood clots when needed
Questions to ask at your visit
- How much protein is in my urine, and is it going up or down?
- What is causing it? Do I need a kidney biopsy?
- Which medicines will lower the protein in my urine?
- What are the goals for my blood pressure and urine protein?
This guide is general education and is not a substitute for medical advice. Talk with Dr. Salim or your care team about your own situation. Informed by patient materials from the National Kidney Foundation; learn more at kidney.org.