Proteinuria - Excess Protein in the Urine

Proteinuria - Excess Protein in the Urine
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Protein in the urine is a sign of impaired kidney function, or occurs for other disease causes. However, some small amount of protein tends to be present in the urine even in the absence of disease.

Protein in the urine, or also technically proteinuria/albuminuria, is the presence of protein in the urine. Normally, even without a disease cause present, very small amounts of protein are found in the urine. However, when values climb, there may be a disease.

What is the normal, ideal value?

Under normal circumstances, slightly elevated levels occur in children, adolescents or pregnant women. But also in people after excessive physical exertion or after stress.

The proteins in the urine come from the blood plasma, when the blood is filtered, from the kidney itself and also from the urinary tract.

Several types of proteins that are important from a diagnostic point of view are mentioned in this issue.

Further, the volume of protein in the urine is influenced by: 

  • age
  • nutrition and protein intake
  • the position of a person, especially in children, which is related to the daily rhythm
  • time of day - orthostatic phenomenon
    • protein excretion during the day is about twice as high as at night
  • physical activity and intensity of muscle work
  • stress
  • amount of blood pressure
  • temperature, fever

During one day, about 180 liters of primary urine is formed in the kidney. But not the entire volume of primary urine is excreted out of the body.

As the primary urine emerges from the glomeruli, or filter cages, most of the fluid is reabsorbed. These 180 litres contain approximately 10 kilograms of protein. Of this, only 0.01%, or 1 gram, passes through the glomerular filtration barrier into the filtrate.

This barrier can be compared to situ.

It is composed of three layers, namely endothelial cells, glomerular basement membrane and podocytes. The proteinuria defect may have a basis in each of these.

Only proteins that are smaller than the aperture of the sieve pass through this sieve. They are also referred to as microproteins (they have a low molecular weight, namely less than Mr < 60 000). And these are reabsorbed and returned to the body, or catabolized (broken down) in the proximal tubule, which is the part behind the filtering glomeruli.

Thus, proteins that have a molecular weight greater than Mr > 60,000 or more than 100,000-150,000 do not normally enter the urine.

In addition to the microporous structure of the glomerular basement membrane, the electrostatic barrier is also involved in filtration.

During normal physical activity and throughout the day, approximately 50 to 89 milligrams of protein are excreted in the urine over a 24-hour period.
Normal, that is, physiological microalbuminuria can be approximately 10 - 30 mg per day.

This type of proteinuria is referred to as: Physiological proteinuria.

Two basic types of proteins are evaluated in urine.
The first is plasma proteins that pass through the filtration barrier.
The second type is non-plasmic proteins, which originate from the renal tubules.

The approximate proportion of protein in the urine:

  • 60% of this is protein from the kidneys, more specifically from the renal pelvis and ureters
    • non-plasmic proteins 
    • this type of protein is also referred to as Tamm-Horsfall protein
    • approximately 25 - 75 mg per day and 1,73 m
    • reduced production may indicate a defect in the marrow of the kidney
  • 40% of which is plasma protein filtered from the blood
    • this end-tidal volume is influenced by the filtration barrier, retrograde resorption and renal haemodynamics 

Proteinuria and what causes it

Protein in the urine, or proteinuria, is a condition where the volume of protein in 24 hours exceeds 150-200 mg.

The maximum value is set at 96 mg/m2 = 150 mg per 24 hours. 
Urinary protein levels above 150 - 200 mg in 24 hours.

According to the quantity it is divided into:

  • mild proteinuria - less than 150 mg in 24 hours
  • temperate proteinuria - 150 to 350 mg in 24 hours
  • severe proteinuria - more than 350 milligrams in 24 hours = a lot of protein in the urine

Table: Distribution of proteinuria + main causes 

Non-pathological It is not a manifestation of kidney disease. It is also referred to as functional or transient proteinuria. Examples include:
  • postural - orthostatic form, when standing there is a higher excretion (excretion) of protein into the urine, occurs mainly in children and adolescents.
  • induced by physical exertion and muscle work
  • stress
  • hunger
  • febrile form - temperature
  • dehydration
Prerenal proteinuria the problem is "in front of the kidneys" There is no fault in the kidneys. An example might be a situation of an increase in lower molecular weight proteins in the blood. These are subsequently passed into the urine, even without the presence of disease. Another cause may be haemolysis, the breakdown of red blood cells. In this case, in addition to protein in the urine, there will also be blood and hemoglobin, hence hematuria.  Another example is the presence of myoglobin, which is a muscle protein, it happens in crash syndrome or rhabdomyolysis and also in acute inflammation or tissue necrosis.
Renal proteinuria Glomerular - an increase in the permeability of the glomerular barrier to proteins. Medium proteins, albumin and transferrin (Mr 70 00 - 100 000) are secreted, but not large proteins - it is a selective form Alternatively, larger proteins above Mr 100 000 may also be secreted, this is referred to as the non-selective form. The causes can be different:
Tubular - caused by reduced protein reabsorption in the tubules of the kidneys. Microproteins, i.e. proteins with low molecular weight, are secreted. Common as:
  • toxic effect of some drugs (field damage), cytostatics, some antibiotics and anti-inflammatory drugs
  • heavy metal poisoning, such as lead, mercury, copper
  • acute tubular necrosis
  • TIN - tubulointerstitial nephritis (a form of inflammation of the kidney) 
  • polycystic kidney disease
  • peylonephritis, a form of inflammation of the kidney
Mixed - combination of both types
Postrenal proteinuria Large proteins and plasma also pass into the urine. Thus, all types of plasma proteins, leukocytes (white blood cells) and haemoglobin, the red blood pigment, are found in the urine. Possible causes include:
  • bleeding and bleeding conditions
  • cancerous disease
  • inflammation of the urinary tract
  • kidney and urinary stones

Symptoms include:

  • kidney and urinary tract diseaseother systemic and metabolic diseases such as lupus, diabetes (diabetic nephropathy)
  • endocarditis (inflammation of the heart) and other heart diseases, heart failure
  • immune disorders and autoimmune diseases, rheuma
  • infections and inflammations
  • high blood pressure
  • certain drugs, chemotherapy
  • toxins
  • trauma and burns
  • tumour and malignant oncological disease, lymphoma, myeloma
  • increased production of proteins in the body, such as amyloidosis
  • dehydration
  • stress and emotional strain
  • excessive physical exertion and strenuous exercise
  • exposure to cold and hypothermia
  • fever and exposure of the body to high temperatures
  • anaemia - sickle cell anaemia
  • in pregnancy and pre/eclampsia
  • excess protein in the diet

Protein in the urine in children

Can there be excess protein in a baby's urine?

In childhood and especially during puberty and adolescence, higher urinary protein counts are possible. The cause does not have to be a disease and happens quite often.

Up to 10% of school-age children may have proteinuria when tested.
Subsequently, after the second test, the prevalence rate drops to 0.1%.
Mostly found in girls.

The cause is the functional form. You will also come across labels such as temporary, functional or orthostatic proteinuria (exercise, stress, fever, increased protein excretion while standing).

It is reported that the orthostatic form is frequent in the period of childhood. It finds its representation in 3 to 5% of adolescents.

In the supine position, protein excretion into the urine is normal. It rises when standing and therefore during the day.

Therefore, a comparison is made of the values of protein in the urine during the night and day.

The cause of orthostatic proteinuria is not fully elucidated.

With an elevated level of protein in the urine, a regular check-up with a doctor is necessary.

However, even at this age it can be a symptom of kidney disease or dysfunction. The literature states that it is often the glomerular and tubular form.

Proteinuria during pregnancy

During pregnancy, there may be a transient increase in the amount of protein in the urine. This happens at the beginning, during and at the end of pregnancy.

However, if it is a long-term occurrence or the value is above 300 mg an examination is necessary. 

Long-term, i.e. chronic proteinuria, in pregnancy occurs already after the 20th week of pregnancy. Mostly it happens with a pre-existing kidney problem.

The acute form arises from a variety of causes, however, the most feared are preeclampsia and eclampsia. There is a risk of endangering both the pregnant woman and the fetus.

Typical symptoms:

The risk is transition and culmination into eclampsia and HELLP syndrome. Body convulsions, breakdown of red blood cells, increase in liver enzymes, decrease in platelet count occur. 

High risk of death of the pregnant woman and the fetus. Requires immediate treatment, the only form of which may be termination of pregnancy.

Minor causes of an increase in protein in the urine during pregnancy:

  • excessive physical activity
  • stress
  • dehydratation
  • fever
  • diabetes

Learm more: 
Protein in the urine during pregnancy? That may or may not be a problem

Other symptoms and syndromes

In addition to the demonstrated elevated protein levels in the urine, the occurrence of other health problems is possible.

An example of symptoms that may accompany proteinuria is:

  • foamy urine, the foam lasts longer
  • frequent urination
  • fatigue
  • weakness and exhaustion
  • swelling, initially of the face and around the eyes, later also of the limbs
  • shortness of breath
  • nausea
  • vomiting
  • pain in the abdomen, lower abdomen, in the flank
    • especially in inflammation
    • also with dysuria, burning, cutting, pinching when urinating
    • frequent urination

Urine in proteinuria:

  • foam on the urine - under normal circumstances, the foam on the urine sticks for a short time
    • white foam, disappears more slowly
  • milky white in colour - presence of both proteins and fats
  • cloudy or pink to red urine if inflammation with haematuria is present

Important concepts used in urinary dysfunction:

  • polyuria - high amount of urine in 24 hours over 2500 ml or 100 ml per hour
  • oliguria - a decrease in the amount of urine below 300 ml in 24 hours
  • anuria, amount of urine below 100 ml in 24 hours, but also cessation of urine production
  • retention - retention of urine, obstruction in the urinary tract
  • polakizuria - frequent urge with urination of a small amount
  • dysuria - difficulty urinating, pain when urinating
  • stranguria - painful urination - burning
  • nocturia - frequent urination at night
  • enuresis nocturna - bedwetting at night
  • urinary incontinence - loss of the ability to control urination and therefore spontaneous passing of urine

How to diagnose and treat?

Diagnosis of proteinuria is also important in terms of treatment. It is often detected incidentally as it is asymptomatic (without symptoms).

Initially, the patient's medical history is taken. It is also important to find out the family history of kidney problems and hereditary diseases.

Subsequently, a physiological examination is carried out, during which it is necessary to know the blood pressure values. Checking for swelling.

Urine is examined. The first option, which is also available for the home test, is the paper method, and thus the test strip (litmus paper). 

The paper test is scored on crosses:

  • 1 + (a single cross) = approximately 300 mg/litre
  • 2 ++ = roughly 1 g/l
  • 3 +++ = roughly 3 g/l
  • 4 ++++ = 20 - 30 g/l

This test is an indicative, screening test.
It may be incorrectly evaluated.
After that, further examination is necessary.

The most important test is the 24-hour urine collection and laboratory evaluation. Plus, other methods such as blood tests (electrolytes, urea, creatinine) will be added. 

Imaging methods include:

  • ultrasound
  • X-ray - contrasting methods
  • CT
  • MRI
  • and other

Once the cause is identified, treatment follows.

Proteinuria can take several forms and this infographic gives an overview:

In case of inflammation, antibiotics are administered. For other diseases, specific therapy for the particular problem. Diet with regard to protein intake and regimen measures are important, which includes rest and avoidance of stress and physical exertion and other risk factors. 

Will tea help for protein in urine? Urological tea can be drunk, the drinking of which is of importance in inflammation of the urinary tract (along with professional treatment). After all, in inflammation, there may be protein in the urine in addition to blood. But, for other diseases its effect is not enough.

Read also: 
Kidneys and kidney diseases
Maintaining your kidneys
Treatment options for kidney stones

Protein in my urine: Should I Worry?

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Interesting resources

  • Khitan, Zeid J.; Glassock, Richard J. (1 October 2019). "Foamy Urine: Is This a Sign of Kidney Disease?". Clinical Journal of the American Society of Nephrology14 (11): 1664–1666. 
  • URINALYSIS Archived 2006-08-16 at the Wayback Machine Ed Friedlander, M.D., Pathologist 
  • Clark WF, Kortas C, Suri RS, Moist LM, Salvadori M, Weir MA, Garg AX (2008). "Excessive fluid intake as a novel cause of proteinuria". Canadian Medical Association Journal178 (2): 173–175. 
  • "Drinking too much water called latest threat to health". Montreal Gazette
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  • Dettmeyer RB, Preuss J, Wollersen H, Madea B (2005). "Heroin-associated nephropathy". Expert Opinion on Drug Safety4 (1): 19–28. 
  • Naesens (2015). "Proteinuria as a Noninvasive Marker for Renal Allograft Histology and Failure: An Observational Cohort Study". J Am Soc Nephrol27 (1): 281–92. 
  • Chou JY, Matern D, Mansfield BC, Chen YT (2002). "Type 1 Glycogen Storage Diseases: Disorders of the Glucose-6-Phosphatase Complex". Current Molecular Medicine2 (2): 121–143. 
  • Fernando, B.S. (June 14, 2008). "A Doctor's Perspective". BMJ336 (7657): 1374–6. 
  • Chapman, A.B.; Johnson, A.M.; Gabow, P.A.; Schrier, R.W. (December 1, 1994). "Overt proteinuria and microalbuminuria in autosomal dominant polycystic kidney disease". Journal of the American Society of Nephrology5 (6): 1349–1354. doi:10.1681/ASN.V561349. 
  • "Urine Protein". Lab Tests Online. Retrieved 2019-05-21.
  • "Globulin". Lab Tests Online. Retrieved 2019-05-22.
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