Albuminuria is a

pathological Pathology is the study of disease. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatme ...

condition of elevated

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All of the proteins of the albumin family are water- soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Alb ...

protein in the

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

(often measured as urine albumin-to-

creatinine Creatinine (; ) is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body (depending on muscle mass). Biological relevance Serum creatinine (a blood measurement) is an impor ...

ratio of >30 milligrams of albumin per 1 gram of creatinine per day). It is a type of

proteinuria Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein, less than 150 mg/day; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become fo ...

, and is the most common protein detected on urinalysis that, when elevated, is associated with kidney and cardiovascular disease (CVD). Albumin is an abundant

plasma protein Plasma proteins, sometimes referred to as blood proteins, are proteins present in blood plasma. They perform many different functions, including transport of hormones, vitamins and minerals in activity and functioning of the immune system. Other b ...

(present in blood) which is normally prevented from being lost into the urine by the sieve-like

glomeruli ''Glomerulus'' (; : glomeruli) is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn". ''Glomerulus'' may refer to ...

of the nephrons. In healthy people, only trace amounts of it are present in urine, but when the filtration system of the kidney is damaged, larger amounts of albumin escape into the urine, which can be quantified and used to determine the extent of kidney injury/

kidney disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease of a kidney. Nephritis is an Inflammation, inflammatory kidney disease and has several types according to the location of the inflammation. Infla ...

Signs and symptoms

Albuminuria is often asymptomatic in low quantities but foamy

may be present. As significant albumin is lost to the urine, swelling of the ankles, hands, belly or face may occur (see

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

and

nephrotic syndrome Nephrotic syndrome is a collection of symptoms due to kidney damage. This includes proteinuria, protein in the urine, hypoalbuminemia, low blood albumin levels, hyperlipidemia, high blood lipids, and significant edema, swelling. Other symptoms ...

). This is because a major role of albumin in the blood is to act as an

osmotic Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region o ...

agent, keeping water from leaving blood vessels and leaking into the surrounding body tissues.

Causes

Albuminuria is not a disease itself but a marker of kidney injury, particularly to the filtration mechanism (glomerulus), and can be caused by a number of pathological states, including: *

Diabetic nephropathy Diabetic nephropathy, also known as diabetic kidney disease, is the chronic loss of kidney function occurring in those with diabetes mellitus. Diabetic nephropathy is the leading cause of chronic kidney disease (CKD) and end-stage renal disease ...

Hypertension Hypertension, also known as high blood pressure, is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not cause symptoms i ...

* Various

autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an " autoimmune disease" ...

disorders **

Lupus nephritis Lupus nephritis is an inflammation of the kidneys caused by systemic lupus erythematosus (SLE) and childhood-onset systemic lupus erythematosus which is a more severe form of SLE that develops in children up to 18 years old; both are autoimmune d ...

IgA nephropathy IgA nephropathy (IgAN), also known as Berger's disease () (and variations), or synpharyngitic glomerulonephritis, is a kidney disease, disease of the kidney (or nephropathy) and the immune system; specifically it is a form of glomerulonephritis o ...

ANCA-associated vasculitis Anti-neutrophil cytoplasmic antibodies (ANCAs) are a group of autoantibodies, mainly of the IgG type, against antigens in the cytoplasm of neutrophils (the most common type of white blood cell) and monocytes. They are detected as a blood test ...

** Anti-GBM disease (Goodpasture's syndrome) **

Membranous nephropathy Membranous glomerulonephritis (MGN) is a slowly progressive disease of the kidney affecting mostly people between ages of 30 and 50 years, usually white people (i.e., those of European, Middle Eastern, or North African ancestry.). It is the sec ...

Antiphospholipid syndrome Antiphospholipid syndrome, or antiphospholipid antibody syndrome (APS or APLS), is an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS can lead to blood clots (thrombosis) in both arteries and veins, pregnancy-relate ...

Alport syndrome Alport syndrome is a genetic disorder affecting around 1 in 5,000–10,000 children, characterized by glomerulonephritis, end-stage kidney disease, and hearing loss. Alport syndrome can also affect the eyes, though the changes do not usually affec ...

** Sjogren syndrome *

Dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...

/ low blood volume *

Cardiovascular disease Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina, heart attack), heart failure, hypertensive heart disease, rheumati ...

* Nephrotoxic medications *

Infections An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

Urinary tract obstruction Urinary tract obstruction is a urologic disease consisting of a decrease in the free passage of urine through one or both ureters and/or the urethra. It is a cause of urinary retention. Complete obstruction of the urinary tract requires prompt tre ...

In all cases, the result is a loss of the kidney's ability to retain albumin from the urine.

Diagnosis/Testing

According to Kidney Disease Improving Global Outcomes (KDIGO) guidelines, albuminuria is categorized into 3 grades with increasing severity of associated kidney injury: A1, A2, and A3. This grading scale, along with

estimated glomerular filtration rate Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearance (medicine), clearing toxins; absorption of glucose, amino acids, and other small molecules; reg ...

, is used to assess risk of progression and severity of kidney disease, particularly in

chronic kidney disease Chronic kidney disease (CKD) is a type of long-term kidney disease, defined by the sustained presence of abnormal kidney function and/or abnormal kidney structure. To meet criteria for CKD, the abnormalities must be present for at least three mo ...

. Various tests are available to measure albuminuria
Urine dipstick analysis
can provide a qualitative estimate of the amount of albumin in the urine sample. More quantitative and accurate testing include
spot sample urinalysis
and
24-hour urine collection analysis

Treatment

Because albuminuria is a sign of underlying kidney injury/disease, treatment should be aimed at the causative factor/s. Common methods of improving and preserving kidney function include medication and lifestyle modifications such as diet and exercise. Blood pressure control, especially with the use of inhibitors of the renin-angiotensin-system, is the most commonly used therapy to control albuminuria.

References

{{Abnormal clinical and laboratory findings for urine Abnormal clinical and laboratory findings for urine