Albuminuria is a pathology condition of elevated serum albumin protein in the urine (often measured as urine albumin-to-creatinine ratio of >30 milligrams of albumin per 1 gram of creatinine per day).
Signs and symptoms
Albuminuria is often asymptomatic in low quantities but foamy
urine may be present. As significant albumin is lost to the urine, swelling of the ankles, hands, belly or face may occur (see
edema and nephrotic syndrome). This is because a major role of albumin in the blood is to act as an
Osmosis 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:
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, is used to assess risk of progression and severity of kidney disease, particularly in chronic kidney disease.
| + KDIGO Albuminuria Categories Based on Urine ACR
! Albuminuria Category
! ACR (mg/mmol)
! ACR (mg/g) |
| A1 (normal to mildly increased) | <3 | <30 |
| A2 (moderately increased) | 3–30 | 30–300 |
| A3 (severely increased) | >30 | >300 |
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 a
spot sample urinalysis and a
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.
