Albuminuria

Albuminuria is a pathological condition wherein the protein albumin is abnormally present in the urine. It is a type of proteinuria. Albumin is a major plasma protein (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. For a number of reasons, clinical terminology is changing to focus on albuminuria more than proteinuria. It is usually asymptomatic but whitish foam may appear in urine. Swelling of the ankles, hands, belly or face may occur if losses of albumin are significant and produce low serum protein levels (nephrotic syndrome). The kidneys 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, especially type 1 diabetes. Recent international guidelines (KDIGO 2012) reclassified chronic kidney disease (CKD) based on cause, glomerular filtration rate 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 results in far less albuminuria. Microalbuminuria (between 30 and 300 mg/24h, mg/L of urine or μg/mg of creatinine) can be a forerunner of diabetic nephropathy. The term albuminuria is now preferred in Nephrology since there is not a "small albumin" (microalbuminuria) or a "big albumin" (macroalbuminuria).. A1 represents normal to mildly increased urinary albumin/creatinine ratio ( 30 mg/mmol). 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.