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Urine Albumin and Microalbuminuria

Introduction

Proteinuria means the presence of protein in the urine. The most common kind of proteinuria is characterised by the presence of albumin in the urine. Normally the kidneys will prevent protein from being excreted into the urine. In circumstances where the blood protein is high, it may appear in the urine even in normal individuals. Contamination from vaginal secretions, urinary tract infection, fever and exercise can also cause transient proteinuria.

In kidney disease, albumin will appear in the urine persistently even with normal blood levels. Urine albumin test measures the amount of albumin in the urine [1]. Urine albumin of more than 300 mg/L is called macroalbuminuria [2]. If it is 30 to 300mg/L, it is called microalbuminuria [2].

Testing urine for the presence of proteinTesting urine for the presence of protein [1]

Microalbuminuria happens when the kidney leaks small amount of albumin into the urine. This is due to abnormally high permeability for albumin in the renal glomerulus.

Urine albumin is tested at least annually in diabetes patients [4]. The aim is to detect early kidney damage.

How to Test for Urine Albumin?

Macroalbuminuria can be diagnosed using a dipstick test. Microalbuminuria is detected using a spot urine sample (positive if 30 to 300 mg/L) or 24-hour urine collection (positive if 30 – 300 mg/24 hours).

At least two out of three measurements over a three to six months period confirms the diagnosis of microalbuminuria [3]. Early morning sample is preferred.

Another method of measuring microalbuminuria is urine albumin/creatinine ratio (ACR). It is positive if ACR >3.5 mg/mmol (female) or >2.5 mg/mmol (male). This method will compensate variations in urine concentration in spot-check sample.

Patient should refrain from heavy exercises 24 hours before the test. The test is inaccurate in individuals with too much or too little muscle mass.

What Does Urine Albumin Indicate?

Urine albumin indicates kidney damage causing protein to leak out and excreted into the urine.

How is Urine Albumin Related to Diabetes?

Diabetes and exposure to chronic hyperglycaemia lead to kidney damage or diabetic nephropathy. Diabetic nephropathy is one of the microvascular complications of diabetes.

Upon diagnosis, type 2 diabetes patient’s progresses to microalbuminuria at the rate of 2.0 percent per year [5]. Subsequently progresses to overt albuminuria (macroalbuminuria – presence of albumin >300mg/L in urine) at the rate of 2.8 percent per year [5].

Can We Treat Diabetic Nephropathy?

Treatment is directed towards preventing further damage to the kidneys. By doing so, progression to end-stage renal failure is delayed.

Microalbuminuria is reversible with drugs such as Angiotensin Converting Enzyme Inhibitors (ACE Inhibitors) and Angiotensin Receptor Blocker (ARB) [6]. These drugs have also shown to delay progression in diabetes patients with macroalbuminuria [6].

Is It Preventable?

Early detection of urine protein requires prompt treatment to preserve as much kidney function as possible.

Optimising glucose control and hypertension management can prevent kidney damage and delay progression.

Other measures to help prevent chronic kidney disease in diabetes patients are :

  • Control of high cholesterol level either by drug or diet-control
  • Maintaining ideal body weight by lifestyle modification
  • Smoking cessation

Conclusion

Urine albumin indicates kidney damage leading to diabetic nephropathy. Kidney damage can progress to end-stage renal failure. It is preventable with appropriate treatment and management of diabetes.

References

  1. http://doctor.ndtv.com/topicdetails/ndtv/tid/50/Urine-albumin.html – accessed 19 September 2012 .
  1. http://en.wikipedia.org/wiki/Microalbuminuria – accessed 19 September 2012 .
  1. Abid O, Sun Q, Sugimoto K, Mercan D, Vincent JL. “Predictive value of microalbuminuria in medical ICU patients: results of a pilot study”. Chest 2001; 120 (6): 1984–8.
  1. http://assets.cardiosource.com/cardiosmart/csp/english/zu1727.pdf – accessed 19 September 2012 .
  1. Amanda I. Adler, Richard J. Stevens, Sue E. Manley, Rudy W. Bilous, Carole A. CullandRury R. Holman, On Behalf Of The UKPDS Group. Development and progression of nephropathy in type 2 diabetes: The United Kingdom Prospective Diabetes Study (UKPDS 64). Kidney International 2003; 63 : 225–232 .
  1. Zandi-Nejad K&Brenner BM.Primary and secondary prevention of chronic kidney disease. J Hypertens 2005; 23(10):1771-6 .

 

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