What is MAU?

Microalbumin appear in the urine. Albumin is a normal protein found in the blood, but only very small amounts appear in the urine under physiological conditions. Microalbumin may reflect abnormalities in the body's proteins, small molecular proteins that are excreted in the urine and difficult to detect by conventional tests.

Under normal conditions, the high molecular weight of albumin does not allow it to cross the glomerular basement membrane, so the amount of albumin in human urine is extremely low.But when the kidney function is impaired, the glomerular basement membrane permeability increases, which may lead to an increase in urinary microalbumin, so when urinary microalbumin increases, it may indicate that there is a kidney problem, which can reflect the early stage of renal disease and kidney injury status.

Clinical application of MAU

Urine microalbumin measurement reflects early renal disease and kidney injury. Pathological increase is seen in diabetic nephropathy, hypertension, pre-eclampsia in pregnancy. Urine microalbumin in the early stage is an early signal and harbinger of kidney disease, at this time the kidney damage is in the period of reversible, if timely treatment, can terminate or reverse the development of kidney disease.

The most ideal method of determining urinary albumin is to leave a 24-hour urine specimen, due to the existence of a large degree of variability in urinary albumin excretion, so undetermined time of urine specimen (casual urine) an increase in albumin excretion may not be meaningful, two to three consecutive increases before diagnosis. An increase in albumin excretion in an untimed urine specimen (casual urine) may be of no significance, but only two or three consecutive increases are diagnostic.

Specific clinical applications of MAU are shown below:

① MAU can infer the severity of glomerular lesions and help in the early diagnosis of glomerular lesions.Microalbumin is markedly elevated when glomerular damage is mild, and the degree of elevation correlates with the degree of glomerular damage.

② MAU is the most sensitive and reliable diagnostic indicator for early detection of kidney disease. Microalbumin levels increase with increasing kidney injury.

③ MAU can be used to monitor drug toxicity, hyperbilirubinaemia and kidney tubular function in newborns.

④ MAU provides a reference for early detection, diagnosis and treatment of diabetic nephropathy and toxic kidney disease, etc. It is a hallmark feature in the development of diabetic kidney disease.

⑤ Microalbumin in patients with chronic heart failure is predictive of chronic renal failure and correlates with poor heart failure prognosis.

⑥ The clinical significance of Microalbumin measurement also allows for the monitoring of selected diseases such as urinary tract infections, diabetic kidney disease, and hypertension and drug-induced kidney injury.

Factors affecting MAU

Increased MAU levels may also be due to:

Primary glomerulonephritis or secondary nephropathy

(Microscopic lesions, nephrotic syndrome, diabetic kidney disease, hypertensive nephropathy)

Urinary tract infection, urinary stones, prostatitis

Fever, severe infection, strenuous exercise, cold

Summary

Urine microalbumin, as a sensitive indicator of early kidney damage, can be considered to be included in the annual mandatory test, especially for patients with diabetes and hypertension. However, if there is only one elevation, it needs to be combined with the clinical situation. If you are not very old and do not have any underlying disease such as diabetes or hypertension, and there are no uncomfortable symptoms, the occurrence of a single elevation of urinary microalbumin may be caused by some functional factors, such as strenuous exercise, improper diet, high fever, and so on.

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References

[1] WANG Mei. Urine microalbumin, detection of early kidney injury[J]. Family medicine. Happy Health,2020,(12):65.

[2] Chinese Medical Association Diabetes Branch. Guidelines for the prevention and treatment of type 2 diabetes mellitus in China (2020 edition)[J]. International Journal of Endocrinology and Metabolism,2021,41(05):482-548.

[3] Singh A. Microalbuminuria: causes and implications. Pediatr Nephrol.2011;26(11):1957-1965.