From the Guidelines
Trace protein in urine is most commonly caused by kidney damage or disease, with increased excretion of albumin being a sensitive marker for chronic kidney disease due to diabetes, glomerular disease, and hypertension. The presence of protein in urine, known as proteinuria, can be caused by several conditions affecting the kidneys or urinary system.
Common Causes of Proteinuria
- Temporary factors like strenuous exercise, dehydration, fever, emotional stress, or exposure to extreme cold
- Kidney diseases such as glomerulonephritis, diabetic nephropathy, or polycystic kidney disease
- High blood pressure damaging kidney filters over time, allowing protein to leak into urine
- Certain medications like non-steroidal anti-inflammatory drugs (NSAIDs) causing temporary proteinuria
- Urinary tract infections or pregnancy-related conditions like preeclampsia resulting in protein appearing in urine According to the National Kidney Foundation practice guidelines for chronic kidney disease 1, increased excretion of albumin is a sensitive marker for chronic kidney disease. The guidelines recommend using the ratio of protein or albumin to creatinine in an untimed urine specimen to measure proteinuria, as it corrects for variations in urinary protein concentration due to hydration and is more convenient than timed urine collections 1.
Evaluation of Proteinuria
The evaluation of proteinuria should begin with testing of a random untimed urine sample with an albumin-specific dipstick, followed by confirmation of proteinuria by measuring the albumin–creatinine ratio on an untimed urine sample within 3 months if the result is positive 1. Patients with two or more positive results on quantitative tests temporally spaced over 3 months have persistent proteinuria and should undergo further evaluation for chronic kidney disease. While trace amounts of protein in urine may not always indicate serious disease, persistent proteinuria should be evaluated by a healthcare provider to determine the underlying cause and appropriate treatment.
From the Research
Causes of Trace Protein in Urine
- Kidney dysfunction is a common cause of trace protein in urine, particularly in patients with type 2 diabetes mellitus 2
- The presence of proteins in urine contributes to kidney dysfunction, and total proteinuria is a significant factor contributing to kidney dysfunction in type 2 diabetes patients 2
- High blood pressure, mean arterial pressure, and pulse pressure are associated with the development of diabetic chronic kidney dysfunction or failure, and are correlated with high levels of spot urine protein 3
- Elevated blood pressure has been demonstrated to be a risk factor for the development of nephropathy and chronic renal disease, and is significantly correlated with urine protein excretion 3
- Logistic regression models have been developed to predict diabetic proteinuria based on systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse pressure, which can be used to estimate protein excretion in urine 3