Microalbuminuria means the presence of a fair amount of albumin in the urine. The finding of microalbuminuria does not indicate the presence of severe kidney damage, but it is still an alarm bell regarding the state of health.
The presence of microalbuminuria indicates that a small amount of albumin is able to pass the renal barrier and ends up in the urine. Microalbuminuria is often associated with the presence of diabetes with renal damage, arterial hypertension, dyslipidemia (excess triglycerides and / or cholesterol) and metabolic syndrome. Let's see in detail what albumin is and why it should not normally be present in urine.
What is albumin
What is albumin? Albumin it is a fundamental protein for our body; is produced by hepatocytes (i.e. the cells of the liver) but we can also find it in milk or egg. It is mainly contained in the plasma blood, of which it constitutes about 60% of total proteins. The main role of this protide is to control the oncotic pressure (which physiologically is 20 mmHg); it is essential to keep its concentration constant to ensure that body fluids are distributed correctly. To simplify the concept, one can imagine albumin as a substance capable of attracting interstitial liquids to itself, to assist the action of the kidney. A single gram of this protein is capable of drawing about 17 grams of water.
In addition to this fundamental task, albumin is capable of to carry many substances, including hormones (including those of the thyroid), hematin, benzene, some types of medications (such as warfarin or penicillin) and the fatty acids with long chain. It is also an efficient one buffer able to give positive charges in conditions of alkalosis (i.e. when the blood is excessively acidic so that the pH decreases below 7.35) and negative charges in conditions of acidosis (i.e. when the blood is characterized by excessive basicity, which causes a increase in pH above 7.45).
What is albuminuria and what does it mean
What does albuminuria mean? With the term albuminuria it indicates an abnormal loss of albumin through the urine ("albumin" indicating albumin and "uria" indicating urine); this condition can be transient or permanent. Physiologically speaking, they should only be there traces of protein in the urine and in these traces there should be an almost imperceptible quantity of albumin (maximum 30 mg of albumin in 24 hours); this substance, in fact, has a negative charge and, since the glomerular membrane is also negative, there is a repulsion between them which, in normal cases, prevents albumin from crossing the renal glomerulus, preventing its passage in the urine. Furthermore, even if the amount of albumin passing through the renal filter was consistent, at the proximal tubule (a kidney tract with high absorbency) much of this protein comes anyway reabsorbed. When all this does not happen, the quantity of albumin excreted in the urine becomes consistent and, therefore, abnormal.
Microalbuminuria and macroalbuminuria: reference values
L'albuminuria can be divided into two groups, both characterized by high albumin concentration: microalbuminuria is macroalbuminuria.
In the case of microalbuminuria, the presence of albumin in the urine is anomalous, but still in modest quantities. Its concentration, in this case, ranges from a minimum of 30 mg to a maximum of 300 mg (24 hour urinalysis). These albeit contained quantities of albumin, can be considered signals for the early diagnosis of some pathologies, as in the case of diabetic nephropathy. If, on the other hand, the values are higher, the real one is incurred proteinuria which indicates high amounts of protein in the urine. Referring in particular to the albumin protein alone, we speak in this case of macroalbuminuria. In a patient with macroalbuminuria, albuminuria values in the urine above 300 mg (collected in 24 hours) will be found. The albumin values present in the urine described above concern quantities found in the urine collected over a whole day, and not in the extemporaneous urine test, that is, not on a single urine sample collected in the early morning.
- Microalbuminuria values: more than 30 mg (or 0.03 g) but less than 300 mg (or 0.3 g) of albumin in the urine over 24 hours
- Macroalbuminuria values: over 300 mg of albumin in the urine over 24 hours
Microalbuminuria and proteinuria: the causes
There are numerous pathologies that can lead to the development of microalbuminuria. The main causes of albuminuria I'm:
- diabetic nephropathy,
- prolonged standing (standing),
- heart failure,
- old age,
- excessive exercise,
- autoimmune diseases such as systemic lupus erythematosus (SLE)
Regarding the diabetic nephropathy, it is a disease that affects patients with diabetes whose kidneys (which are responsible for the content and concentration of substances in the urine) are permanently damaged.
There glomerulonephritis, instead, it is an inflammation affecting the glomeruli of the kidneys whose main causes have been autoimmune diseases, infections and diabetes mellitus. The symptoms of this pathology are hypertension, renal insufficiency and, indeed, proteinuria.
As for the orthostatic proteinuria, it must be said that it is often present in adolescence and is evident because, in an upright position, the excretion of body proteins increases. In most cases, orthostatic proteinuria disappears over the years (usually between 16 and 18 years of age).
L'heart failureinstead, it causes the heart to fail to supply all compartments of the body with the blood it needs. Many organs suffer from this inability and, with regard to the kidneys, inadequate renal perfusion often occurs.
Regarding the older patients, if they are not suffering from other diseases that can cause proteinuria, it is time to do its job, as over the years the filtration capacity of the kidney membrane decreases.
Me too'hyperuricemia (i.e. high concentrations of uric acid in the blood), can cause the onset of micro and macroalbuminuria, since interstitial fibrosis occurs in the kidneys which damages its barrier.
Finally also with regard to the Systemic lupus erythematosus, often in this autoimmune pathology tissue damage also affects the kidney, with the onset of glomerulopathy and more or less relevant proteinuria.
There are also some cases in which proteinuria occurs transiently. This is the most common form and is caused by stress or intense sporting activity. In these cases, in fact, the excretion of proteins increases considerably.
Albuminuria as a cardiovascular risk factor
From a HOPE study it emerged that (even if the patient is not suffering from diabetes mellitus) albuminuria is a fundamental factor concerning the cardiovascular risk. This condition, in fact, does not only concern pathologies of the kidney, as it increases the probability of strokes and heart attacks, or that there is an increase in ventricular mass. In addition to urine tests, in many cases other tests such as echocardiography, echocardiography and blood tests including kidney function (urea, creatinine, sodium, potassium), protein profile (total proteins, albumin, alpha globulins, beta globulins, gamma globulins), and impromptu urinalysis.
Albuminuria / creatininuria ratio
- Albumin / Creatinine in humans: normal if between 3.5 and 35
- Albumin / Creatinine in women: normal if between 2.5 and 25
The relationship between albuminuria and creatininuria is used to diagnose both microalbuminuria and proteinuria. It is in fact an examination that analyzes the relationship between these two substances and, based on the results, the presence of these pathologies can actually be highlighted.
If microalbuminuria is present, the albumin-creatinine ratio is normally between 3.5 and 35 in men and between 2.5 and 25 in women. This difference is due to the fact that men, having greater muscle mass, have a higher concentration of creatinine in the urine. If, on the other hand, the values are higher than 25 (in women) and 35 (in men), we speak of macroalbuminuria.
Microalbuminaria: the consequences
The microalbuminaria causes some important consequences, such as the presence in patients suffering from foamy urine, or excessive swelling of some areas of the body such as the legs (especially the ankles and feet) or the face. It causes, many times, an increase in body weight, and there may also be a reduced tolerance to exertion (onset of shortness of breath even after a few steps of stairs or after a short walk). Other times, however, this pathology is completely asymptomatic (ie no symptoms present), only a urinalysis can ensure that it is present or not.
Microalbuminaria what to do? remedies and care
After having undergone the necessary tests, the doctor can, together with the patient, choose an appropriate treatment. There are different types of therapies which vary according to the severity of the disease. When diabetes is downstream of the problem, the prescribed treatment will include a diet low in carbohydrates and, if necessary, oral or insulin hypoglycemic therapy, in order to avoid further damage to the kidneys.
In case of arterial hypertension, therapy will be aimed at restoring normal blood pressure values, using antihypertensive drugs (ace inhibitors, sartans, calcium antagonists, beta blockers) and / or diuretics. When the cause is a kidney infection, antibiotics may be prescribed. A fundamental aspect not to be overlooked in these cases is the diet. It is advisable not to use too much salt, to limit highly sugary drinks (such as tea) to the maximum, try to consume a lot of fruit and vegetables and, especially if you are obese, implement a program to achieve a moderate but progressive weight loss (loss of weight).