When healthy kidneys filter fluids, minerals, and wastes from the blood, they typically prevent large amounts of serum protein from entering the urine. However, when kidney function is impaired, proteinuria occurs, indicating an abnormal presence of protein in the urine.
The two main groups of serum proteins in the blood are albumin and globulins. Albumin constitutes over 50 percent of all serum proteins and plays a crucial role in regulating water balance and transporting certain substances in the blood. Globulins, including alpha, beta, and gamma globulins, have various functions, such as substance transport and immune system support. Proteinuria testing can encompass all types of proteins or focus solely on albumin.
Transient proteinuria is a temporary increase in protein excretion often triggered by factors like strenuous exercise, high fever, cold exposure, stress, or pregnancy. It does not indicate underlying kidney disease and usually requires no treatment.
Orthostatic proteinuria involves increased protein excretion when a person is in an upright position, primarily affecting tall, thin individuals below 30 years of age. Kidneys are typically healthy in such cases.
Overflow proteinuria is caused by non-kidney diseases like multiple myeloma, a type of bone marrow cancer, which floods the blood with excess proteins subsequently filtered into the urine.
The other form of proteinuria results from kidney diseases such as glomerulonephritis, primary focal segmental glomerulosclerosis (FSGS), or kidney damage due to systemic conditions. Microalbuminuria indicates low levels of albumin in the urine and may signify early kidney disease in individuals with diabetes or hypertension.
Proteinuria typically presents no symptoms and is often detected through routine screenings, especially in individuals with high blood pressure or diabetes. In severe cases, protein loss may lead to swelling or edema in various body parts, including the face, eyes, limbs, hands, and feet. Additional symptoms can include foamy urine, weight gain due to fluid retention, diminished appetite, and hypertension.
Urinalysis involves various tests on urine, which can reveal the presence of cells and urinary casts, providing insights into underlying kidney disease.
The Urine Albumin to Creatinine Ratio (UACR) estimates daily albumin excretion without requiring a full-day urine collection.
Common blood tests for proteinuria assess serum creatinine, albumin, cholesterol, and blood glucose levels to identify potential kidney damage.
If kidney disease is suspected, tests such as Glomerular Filtration Rate (GFR) measurement, renal ultrasound scans, or kidney biopsies may be conducted to assess kidney function and structure.
Since proteinuria is a symptom and not a standalone disease, treatment focuses on addressing the underlying condition. This may involve normalizing blood pressure for individuals with hypertension or controlling blood sugar levels in those with diabetes.
For people with nephrotic syndrome and fluid overload, dietary salt restriction may be recommended, along with a mild restriction in protein intake.
ACE inhibitors are medications primarily used to treat hypertension but are also effective in reducing proteinuria, regardless of blood pressure levels.
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