From the Guidelines
Proteinuria is a significant indicator of kidney problems and requires immediate medical attention to prevent progressive kidney damage and potential complications. The presence of proteins in urine can be a sign of kidney disease, diabetes complications, high blood pressure, or other medical conditions 1. According to the national kidney foundation practice guidelines for chronic kidney disease, patients with persistent proteinuria should undergo further evaluation for chronic kidney disease 1.
Evaluation and Diagnosis
The evaluation of proteinuria in patients not known to have kidney disease involves a cutoff value for an albumin–creatinine ratio greater than 30 mg/g in men and women, although some studies suggest sex-specific cutoff values 1. The standard dipstick for protein and the untimed urine measurements for total protein-creatinine ratio are useful for detecting proteinuria in adults not at increased risk for developing chronic kidney disease. However, adults at increased risk for chronic kidney disease with a negative result for protein on a standard dipstick test, especially those with diabetes, should undergo testing with either an albumin-specific dipstick or an untimed urine measurement for the albumin–creatinine ratio 1.
Treatment and Management
Treatment of proteinuria depends on the underlying cause and may include blood pressure medications like ACE inhibitors or ARBs, typically starting at low doses and titrating up as needed. Managing diabetes with proper glucose control, reducing salt intake, maintaining a healthy weight, and avoiding medications that may harm kidneys are also important 1. Early detection and treatment are crucial to prevent progressive kidney damage and potential complications.
Key Considerations
- Proteinuria occurs when the kidney's filtering units (glomeruli) become damaged, allowing proteins that should remain in the bloodstream to leak into the urine.
- Monitoring proteinuria in adults with chronic kidney disease should use the albumin–creatinine ratio or total protein-creatinine ratio if the albumin–creatinine ratio is high (>500 to 1000 mg/g) 1.
- The guidelines review causes of false-positive and false-negative results in measuring urinary albumin or total protein, emphasizing the importance of accurate testing and evaluation 1.
From the FDA Drug Label
The primary endpoint of the study was the time to first occurrence of any one of the following events: doubling of serum creatinine, end-stage renal disease (ESRD) (need for dialysis or transplantation), or death. Almost all of the patients (96.6%) had a history of hypertension, and the patients entered the trial with a mean serum creatinine of 1. 9 mg/dL and mean proteinuria (urinary albumin/creatinine) of 1808 mg/g at baseline. Compared with placebo, losartan significantly reduced proteinuria by an average of 34%, an effect that was evident within 3 months of starting therapy, and significantly reduced the rate of decline in glomerular filtration rate during the study by 13%, as measured by the reciprocal of the serum creatinine concentration
The implications of proteinuria are:
- Doubling of serum creatinine: Proteinuria is associated with an increased risk of doubling of serum creatinine, which is a marker of kidney disease progression.
- End-stage renal disease (ESRD): Proteinuria is also associated with an increased risk of ESRD, which requires dialysis or transplantation.
- Kidney disease progression: The presence of proteinuria indicates kidney damage and is a predictor of kidney disease progression.
- Increased risk of cardiovascular events: Although not directly stated in the label, the presence of proteinuria is often associated with an increased risk of cardiovascular events, such as heart failure, myocardial infarction, and stroke, in other clinical contexts. The use of losartan can help reduce proteinuria by an average of 34%, which can slow the progression of kidney disease and reduce the risk of ESRD and cardiovascular events 2.
From the Research
Implications of Proteinuria
The presence of proteins in urine, also known as proteinuria, can have various implications for an individual's health. Some of the key implications include:
- Increased risk of progression of chronic kidney disease 3, 4, 5
- Association with more serious renal diseases, such as glomerulonephritis and multiple myeloma 3
- Independent risk factor for cardiovascular morbidity and mortality 6
- Potential indicator of underlying systemic disease or renal disease 7
Types of Proteinuria
There are different types of proteinuria, including:
- Transient (functional) proteinuria, which is temporary and resolves when the inciting factor is removed 4
- Orthostatic proteinuria, which is a benign condition that normalizes in the recumbent position 4, 7
- Persistent proteinuria, which can be glomerular or tubulointerstitial in origin and may be associated with more serious renal diseases 4
- Isolated proteinuria, which may be benign or have a worrisome prognosis 7
Evaluation and Diagnosis
The evaluation and diagnosis of proteinuria involve:
- Urine dipstick test as a screening method 4
- Quantitative measurement of urinary protein, such as 24-hour urine protein excretion or urine protein-to-creatinine ratio 3, 4
- Laboratory tests, such as blood work and imaging studies, to determine the underlying cause of proteinuria 3, 4
- Referral to a nephrologist or pediatric nephrologist for further evaluation and treatment 3, 4
Treatment and Management
The treatment and management of proteinuria depend on the underlying cause and may involve:
- Antihypertensive therapy to achieve a blood pressure goal of less than 130/80 mm Hg 6
- Use of drugs that interfere with the renin-angiotensin system, such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers 6
- Lifestyle modifications, such as diet and exercise, to manage underlying conditions and slow disease progression 6