Microalbuminuria

Overview
Microalbuminuria occurs when the kidney leaks small amounts of albumin into the urine, in other words, when there is an abnormally high permeability for albumin in the renal glomerulus.

Diagnosis
The level of albumin protein produced by microalbuminuria cannot be detected by urine dipstick methods. A microalbumin urine test determines the presence of the albumin in urine. In a properly functioning body, albumin is not normally present in urine because it is retained in the bloodstream by the kidneys.

Microalbuminuria is diagnosed either from a 24-hour urine collection (between 30-300 mg/24 hours) or, more commonly, from elevated concentrations in a spot sample (30 to 300 mg/L). Both must be measured on at least two of three measurements over a two- to three-month period. . An albumin level above these values is called "macroalbuminuria", or sometimes just albuminuria.

To compensate for variations in urine concentration in spot-check samples, it is more typical in the United Kingdom to compare the amount of albumin in the sample against its concentration of creatinine. This is termed the albumin/creatinine ratio (ACR) and microalbuminuria is defined as ACR ≥3.5 mg/mmol (female) or ≥2.5 mg/mmol(male), or, with both substances measured by mass, as an ACR between 30 and 300 µg albumin/mg creatinine.

Significance

 * Microalbuminuria is an indicator of subclinical cardiovascular disease
 * Microalbuminuria is a marker of vascular endothelial dysfunction
 * Microalbuminuria is an important prognostic marker for kidney disease particularly in
 * diabetes mellitus
 * hypertension
 * Increasing microalbuminuria during the first 48 hours after admission to an intensive care unit is associated with an elevated risk for acute respiratory failure, multiple organ failure, and overall mortality
 * Microalbuminuria is a risk factor for venous thromboembolism