Albuminuria is a

pathological Pathology is the study of the causal, causes and effects of disease or injury. 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 us ...

condition wherein the protein

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

is abnormally present in the

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

. It is a type of

proteinuria Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become foamy (although this symptom ma ...

. Albumin is a major

plasma protein Blood-proteins, also termed plasma proteins, are proteins present in blood plasma. They serve many different functions, including transport of lipids, hormones, vitamins and minerals in activity and functioning of the immune system. Other blood pr ...

(normally circulating in the blood); in healthy people, only trace amounts of it are present in urine, whereas larger amounts occur in the urine of patients with

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

. For a number of reasons, clinical terminology is changing to focus on albuminuria more than proteinuria.

Signs and symptoms

It is usually asymptomatic but whitish foam may appear in

. Swelling of the ankles, hands, belly or face may occur if losses of albumin are significant and produce low serum protein levels ( nephrotic syndrome).

Causes

The

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...

s normally do not filter large molecules into the urine, so albuminuria can be an indicator of damage to the kidneys or excessive salt intake. It can also occur in patients with long-standing

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

, especially

type 1 diabetes Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin (beta cells) are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar ...

. Recent international guidelines
KDIGO 2012
reclassified

chronic kidney disease Chronic kidney disease (CKD) is a type of kidney disease in which a gradual loss of kidney function occurs over a period of months to years. Initially generally no symptoms are seen, but later symptoms may include leg swelling, feeling tired, vo ...

(CKD) based on cause,

glomerular filtration rate Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood p ...

category, and albuminuria category (A1, A2, A3). Causes of albuminuria can be discriminated between by the amount of protein excreted. * The nephrotic syndrome usually results in the excretion of about 3.0 to 3.5 grams per 24 hours. *

Nephritic syndrome Nephritic syndrome is a syndrome comprising signs of nephritis, which is kidney disease involving inflammation. It often occurs in the glomerulus, where it is called glomerulonephritis. Glomerulonephritis is characterized by inflammation and t ...

results in far less albuminuria. *

Microalbuminuria Microalbuminuria is a term to describe a moderate increase in the level of urine albumin. It occurs when the kidney leaks small amounts of albumin into the urine, in other words, when an abnormally high permeability for albumin in the glomerulus o ...

(between 30 and 300 mg/24h,Page 291
in: mg/L of urinePerson—microalbumin level (measured)
at Australian Institute of Health and Welfare. 01/03/2005 or μg/mg of creatinine
) can be a forerunner of

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 causes of chronic kidney disease (CKD) and end-stage renal disease ...

. The term albuminuria is now preferred in Nephrology since there is not a "small albumin" (''micro''albuminuria) or a "big albumin" (''macro''albuminuria). A1 represents normal to mildly increased urinary albumin/creatinine ratio (<30 mg/g or < 3 mg/mmol); A2 represents moderately increased urinary albumin/creatinine ratio (30–300 mg/g or 3–30 mg/mmol, previously known as

microalbuminuria Microalbuminuria is a term to describe a moderate increase in the level of urine albumin. It occurs when the kidney leaks small amounts of albumin into the urine, in other words, when an abnormally high permeability for albumin in the glomerulus o ...

); and A3 reflects severely increased urinary albumin/creatinine ratio >300 mg/g or > 30 mg/mmol).

Diagnosis

The amount of protein being lost in the urine can be quantified by collecting the urine for 24 hours, measuring a sample of the pooled urine, and extrapolating to the volume collected. Also a urine dipstick test for

can give a rough estimate of albuminuria. This is because albumin is by far the dominant plasma protein, and

bromophenol blue Bromophenol blue (3′,3″,5′,5″-tetrabromophenolsulfonphthalein, BPB), albutest is used as a pH indicator, an electrophoretic color marker, and a dye. It can be prepared by slowly adding excess bromine to a hot solution of phenolsulfonph ...

the agent used in the

dipstick A dipstick is one of several measurement devices. Some dipsticks are dipped into a liquid to perform a chemical test or to provide a measure of quantity of the liquid. Since the late 20th century, a flatness/levelness measuring device trademarke ...

is specific to albumin.

Treatment

Though there is some evidence that dietary interventions (to lower

red meat In gastronomy, red meat is commonly red when raw and a dark color after it is cooked, in contrast to white meat, which is pale in color before and after cooking. In culinary terms, only flesh from mammals or fowl (not fish) is classified as ...

intake) can be helpful in lowering albuminuria levels, there is currently no evidence that low protein interventions correlate to improvement in kidney function.Pan Yu et al. "Low-protein diet for diabetic nephropathy: a meta-analysis of randomized controlled trials." American Journal of Clinical Nutrition 88 (2008): 660-666. Among other measures, blood pressure control, especially with the use of inhibitors of the renin-angiotensin-system, is the most commonly used therapy to control albuminuria.

References

External links

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