Published: 18 Jun 2025

ICD9: 791.0      ICD10: R80.9      ICD11: MF96.Z

Proteinuria, also known as albuminuria (especially when referring to albumin specifically), refers to the presence of an abnormally high level of protein in the urine.
Normally, the kidneys are very good at filtering waste products from the blood while retaining essential substances like protein. When the kidneys aren't functioning properly, protein can leak into the urine.

Here's a breakdown:

What it is: Proteinuria is a sign that the kidneys are not filtering blood as they should.

Albuminuria: Albumin is a specific type of protein. When you see "albuminuria," it specifically means that albumin is present in the urine in an abnormal amount. Since albumin is the most abundant protein in blood, it's often the first protein to appear in the urine when kidney function is impaired. Therefore, albuminuria is often used interchangeably with proteinuria, especially in early stages of kidney disease.

How it's detected: Proteinuria is usually detected through a urine test. This can be a simple dipstick test in a doctor's office, or a more quantitative test that measures the amount of protein in a 24-hour urine sample. The albumin-to-creatinine ratio (ACR) in a spot urine sample is also a commonly used test, as it corrects for urine concentration.

Causes: There are many potential causes, ranging from benign to serious:

Transient proteinuria: This is temporary and often not a sign of kidney disease. Causes include:
Dehydration
Fever
Strenuous exercise
Stress
Exposure to cold

Orthostatic proteinuria: Proteinuria occurs when a person is upright but disappears when lying down. It's more common in adolescents and young adults, and usually isn't harmful.

Persistent proteinuria: This indicates an underlying kidney problem. Common causes include:
Diabetes: Diabetic nephropathy (kidney damage due to diabetes) is a leading cause.
High blood pressure (Hypertension): Hypertension can damage the kidneys over time.
Glomerulonephritis: Inflammation of the glomeruli (the filtering units of the kidneys). Many different types exist.
Polycystic kidney disease: A genetic disorder that causes cysts to form in the kidneys.
Lupus: An autoimmune disease that can affect the kidneys.
Certain medications: Some drugs can damage the kidneys.
Multiple myeloma: A cancer of plasma cells that can lead to protein in the urine.
Preeclampsia: Occurs during pregnancy and causes high blood pressure and proteinuria.

Symptoms: Proteinuria often has no noticeable symptoms, especially in the early stages. As kidney function declines, symptoms may include:

Foamy urine (due to the presence of protein)
Swelling (edema) in the feet, ankles, hands, and face
Fatigue
Loss of appetite
Nausea
More frequent urination

Diagnosis: Diagnosis typically involves:

Urine tests: To confirm and quantify the protein in the urine.
Blood tests: To assess kidney function (e.g., creatinine, BUN) and look for other signs of disease.
Blood pressure measurement: To check for hypertension.
Imaging tests: Ultrasound, CT scan, or MRI to visualize the kidneys and look for structural abnormalities.
Kidney biopsy: In some cases, a biopsy may be needed to determine the cause of the proteinuria.

Treatment: Treatment depends on the underlying cause. It may involve:

Managing underlying conditions: Controlling blood sugar in diabetes, managing high blood pressure, and treating autoimmune diseases.
Medications: ACE inhibitors or ARBs (angiotensin receptor blockers) are often prescribed to help lower blood pressure and protect the kidneys.
Dietary changes: A low-sodium diet may help reduce swelling. In some cases, a low-protein diet may be recommended, but this should be discussed with a doctor or registered dietitian.
Lifestyle changes: Regular exercise, weight management, and avoiding smoking.

Importance: Detecting and treating proteinuria is important because it can be a sign of early kidney disease. Early intervention can help slow the progression of kidney disease and prevent complications. Untreated proteinuria can lead to chronic kidney disease (CKD) and eventually kidney failure.

In summary: Proteinuria (albuminuria) is the presence of too much protein in the urine. It's often a sign of kidney damage and can be caused by various factors. It's crucial to get it checked out by a doctor if you suspect you have it, as early detection and treatment can help protect your kidneys.