From the Guidelines
Proteinuria is primarily caused by kidney damage or dysfunction, with the most common causes being diabetes and high blood pressure, as supported by the National Kidney Foundation practice guidelines 1. The causes of proteinuria can be categorized into several groups, including:
- Chronic diseases such as diabetes and hypertension, which can damage the kidney's filtering units over time
- Kidney diseases like glomerulonephritis, lupus nephritis, and amyloidosis
- Certain medications, including NSAIDs
- Temporary conditions like dehydration, fever, extreme exercise, and emotional stress
- Pregnancy-related conditions, such as preeclampsia According to the National Kidney Foundation guidelines 1, monitoring proteinuria in adults with chronic kidney disease should use the albumin–creatinine ratio or total protein-creatinine ratio, which helps in detecting and managing kidney damage. The severity of proteinuria can range from mild transient proteinuria to nephrotic syndrome, and treatment focuses on addressing the underlying cause, which may include controlling blood pressure with medications, managing diabetes, adjusting medications, or treating specific kidney diseases 1. It is essential to note that persistent proteinuria requires medical evaluation as it may indicate serious kidney disease that could progress to kidney failure if left untreated, emphasizing the importance of early detection and treatment, as highlighted in the National Kidney Foundation guidelines 1.
From the Research
Causes of Proteinuria
- Proteinuria may be associated with a renal or systemic disease, or it may be isolated 2
- It can be caused by nonpathological processes such as posture, fever, or exercise, or by pathological processes such as glomerular or tubular diseases 3
- Glomerular proteinuria is an early sign of kidney disease and may also play a role in the progression of glomerular damage 3
- Proteinuria can originate from prerenal, renal, and postrenal causes, and can be the result of impaired tubular protein reabsorption or glomerular filtration barrier dysfunction 4
Types of Proteinuria
- Isolated proteinuria can be subdivided into benign forms with a favorable prognosis and persistent forms with a worrisome prognosis 2
- Functional proteinuria may occur in disorders with altered renal hemodynamics and usually resolves without progressive renal disease 2
- Persistent isolated proteinuria represents a heterogeneous group, but a significant proportion of these patients have prominent renal pathologic findings and progress to serious renal disease 2
- Nephrotic-range proteinuria is generally associated with glomerular disorders, while non-nephrotic range proteinuria may be associated with tubulointerstitial or vascular disorders 2
Physiological and Pathophysiological Mechanisms
- The glomerular filtration barrier prevents the abnormal passage of albumin and high-molecular-weight proteins, while low-molecular-weight proteins can pass through almost unrestricted 4
- Proteins that arrive in the tubular lumen are reabsorbed by endocytosis after binding to the megalin-cubilin complex, and an increased load of proteins can lead to saturation of the reabsorptive mechanism and higher urinary protein excretion 4
- Elevated tubular protein concentrations can be toxic to tubular cells and are associated with the progression of chronic renal disease 4