Albuminuria is the medical term for the presence of albumin, a type of protein, in the urine. Albumin is the most abundant protein in human blood plasma, where it performs several functions, including maintaining the pressure within blood vessels and transporting substances throughout the body. In a healthy individual, the kidneys act as filters, cleaning waste from the blood while preventing larger molecules like albumin from passing into the urine. The detection of albumin in the urine serves as an indicator that the kidneys’ filtration barrier may be compromised.
Associated Health Conditions
The appearance of albumin in the urine is not a disease itself but a sign that an underlying health issue has affected the kidneys. Chronic conditions, particularly diabetes and high blood pressure (hypertension), are the most frequent causes. Both conditions can inflict damage over time on the small blood vessels within the kidneys’ filtering units, known as the glomeruli. This damage impairs the glomeruli’s ability to separate waste products from essential proteins.
In diabetes, high blood sugar levels contribute to a process called glomerulosclerosis, which is a scarring of these tiny blood vessels. Similarly, chronic hypertension exerts excessive force on the arteries that supply the kidneys. This sustained pressure can weaken and damage the glomerular vessels, allowing albumin to leak from the bloodstream into the urine.
While diabetes and hypertension are the primary drivers, other conditions can also lead to albuminuria. These include primary kidney diseases that directly attack the glomeruli, such as glomerulonephritis. Certain autoimmune diseases, like lupus, can cause the immune system to attack kidney tissues. Conditions that affect the heart’s ability to pump blood, such as heart failure, can contribute to kidney damage and subsequent albuminuria.
Identification and Measurement
Because albuminuria in its early stages often produces no noticeable symptoms, its identification relies on specific testing and routine screening for those with risk factors. When symptoms do appear, they can include foamy urine or swelling in the hands, feet, abdomen, or face.
The standard method for detecting and measuring albuminuria is a urine test called the urine albumin-to-creatinine ratio, or UACR. This test measures the amounts of both albumin and creatinine, a waste product of muscle metabolism. Measuring creatinine alongside albumin provides a more accurate assessment, as it accounts for variations in urine concentration due to hydration levels.
The results of the UACR test are used to classify the extent of albuminuria. A result below 30 milligrams per gram (mg/g) is considered normal. Results between 30 and 300 mg/g indicate moderately increased albuminuria, a stage sometimes referred to as microalbuminuria. A reading above 300 mg/g is classified as severely increased albuminuria, or macroalbuminuria, signaling more significant damage.
Medical and Lifestyle Management
The management of albuminuria focuses on treating the underlying cause and implementing strategies to protect the kidneys from further damage. This approach involves a combination of medication and specific lifestyle adjustments aimed at lowering pressure within the kidneys and reducing cardiovascular risk. The primary goal is to slow the progression of kidney disease.
Medications are a central component of treatment. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are commonly prescribed. These drugs work by relaxing blood vessels, which lowers blood pressure and reduces pressure inside the glomeruli, thereby decreasing the amount of albumin that leaks into the urine. For individuals with diabetes, SGLT2 inhibitors may also be used to help manage blood sugar and provide additional kidney protection.
Lifestyle modifications are important for managing albuminuria. This includes careful management of blood pressure and blood glucose levels through diet and medication. Adopting a diet low in sodium is often recommended to help control blood pressure. Regular physical activity, maintaining a healthy weight, and quitting smoking are other changes that can improve overall kidney health.