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.

Additional recommended knowledge

How to quickly check pipettes?

Weighing the right way

Don't let static charges disrupt your weighing accuracy

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