Urine protein measurement assesses the amount of protein present in a urine sample. Healthy kidneys allow very little protein to pass through their filtration membranes — the glomeruli — and reabsorb almost all that does pass through in the tubules. Only trace amounts (less than 150mg per day) are normally excreted.
Persistent proteinuria (elevated protein in urine) is one of the most important markers of kidney disease, indicating that the glomerular filtration barrier has been damaged. It occurs in diabetic nephropathy, glomerulonephritis, hypertensive kidney disease, and nephrotic syndrome. Proteinuria is also an independent risk factor for cardiovascular disease. Transient proteinuria can occur with fever, intense exercise, or dehydration — so persistent findings are more clinically significant.
FAQs
Why is urine protein a cardiovascular risk factor?
Proteinuria indicates endothelial and glomerular dysfunction that reflects systemic vascular disease. Even microalbuminuria (low-level protein loss) independently predicts cardiovascular events beyond its association with kidney disease.
What is the ACR test?
The albumin-to-creatinine ratio (ACR) is measured on a spot urine sample and corrects for urine concentration. It is more sensitive and convenient than 24-hour urine collection for detecting microalbuminuria and monitoring kidney disease.
Can exercise cause protein in urine?
Yes. Strenuous exercise can cause transient proteinuria lasting 24-48 hours. Urine protein should be re-tested after 48 hours of rest. Persistent proteinuria independent of exercise is clinically significant.
What is orthostatic proteinuria?
A benign condition in young adults where protein appears in urine only when upright. Testing a first morning specimen (collected after lying down all night) shows no protein, confirming the orthostatic pattern.
