Microalbuminuria

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

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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 filtered from the bloodstream by the kidneys.

Microalbuminuria is diagnosed either on 24-hour urine collections (20 to 200 µg/min) or, more commonly, if elevated concentrations (30 to 300mg/L) on at least two occasions.^[1]. Albumin levels above these values is called "macroalbuminuria", or sometimes just albuminuria.

To compensate for the variable possible urine concentration on spot-check samples, it is more typical in the UK 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 ≥2.5 mg/mmol (male) or ≥3.5 mg/mmol(female).^[2]

Significance

• an indicator of subclinical cardiovascular disease
• marker of vascular endothelial dysfunction
• an important prognostic marker for kidney disease
  • in diabetes mellitus
  • in hypertension
• increasing microalbuminuria level during the first 48 hours after admission to an intensive care unit predicts elevated risk for acute respiratory failure , multiple organ failure , and overall mortality

References

• Abid O, Sun Q, Sugimoto K, Mercan D, Vincent JL (2001). "Predictive value of microalbuminuria in medical ICU patients: results of a pilot study". Chest 120 (6): 1984-8. PMID 11742932.

• Andersen S, Blouch K, Bialek J, Deckert M, Parving HH, Myers BD (2000). "Glomerular permselectivity in early stages of overt diabetic nephropathy". Kidney Int. 58 (5): 2129-37. doi:10.1111/j.1523-1755.2000.00386.x. PMID 11044234.

• Heart Outcomes Prevention Evaluation Study Investigators (2000). "Effects of ramipril on cardiovascular and microvascular outcomes in people with diabetes mellitus: results of the HOPE study and MICRO-HOPE substudy.". Lancet 355 (9200): 253-9. PMID 10675071.

• Lemley KV, Abdullah I, Myers BD, et al (2000). "Evolution of incipient nephropathy in type 2 diabetes mellitus". Kidney Int. 58 (3): 1228-37. doi:10.1046/j.1523-1755.2000.00223.x. PMID 10972685.

• Lièvre M, Marre M, Chatellier G, et al (2000). "The non-insulin-dependent diabetes, hypertension, microalbuminuria or proteinuria, cardiovascular events, and ramipril (DIABHYCAR) study: design, organization, and patient recruitment. DIABHYCAR Study Group". Controlled clinical trials 21 (4): 383-96. PMID 10913814.

• Parving HH, Lehnert H, Bröchner-Mortensen J, Gomis R, Andersen S, Arner P (2001). "The effect of irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes". N. Engl. J. Med. 345 (12): 870-8. PMID 11565519.

See also

• albuminuria