Oxalates in the urine

Oxalates in urine are calcium or ammonium oxalate, that is, salts of organic oxalic acid, which belongs to the class of dibasic carboxylic acids.

These salts are present among more than one hundred and fifty chemical substances that make up urine.

In nephrological practice, clear symptoms that a patient has too many oxalates in the urine include pollakiuria (frequent urination), polyuria (increased urine volume), fatigue, abdominal pain and renal colic.

But in many cases such clinical manifestations are not observed, and the metabolic disorder progresses in the meantime... Its almost inevitable result is the formation of concretions (stones) in the kidneys or bladder. 76% of these stones are an inorganic compound, calcium oxalate, insoluble in biological fluids in the urine.

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Oxalates in urine during pregnancy

The content of salts, including calcium oxalate in urine, usually decreases during pregnancy.

And if oxalates in urine during pregnancy exceed the norm, then the reasons may be in the same kidney problems, as well as emerging or exacerbated inflammatory diseases of the urinary tract. The symptoms of oxaluria are the same: pollakiuria and polyuria, increased fatigue and painful sensations in the lower abdominal cavity.

In addition, oxalates in urine during pregnancy may appear due to the desire to "saturate" the body with vitamins (for the benefit of the future child) and excessive consumption of vegetables and fruits rich in oxalic acid. Another reason is that pregnant women often reduce fluid intake - to combat edema. This reduces urine formation, but helps to increase its concentration. What to do with oxalates in the urine of pregnant women? Find a reasonable compromise in the question of "to drink or not to drink" and be sure to establish proper nutrition with oxalates in the urine (which will be discussed below).

Oxalates in urine in a child

Oxalates may be present in small amounts in the urine of a child (as well as in adults). But metabolic disorders in the kidneys of children, unfortunately, are being diagnosed more and more often.

Let's start with a rather rare but very severe case of increased oxalate content in the urine of a newborn - a congenital anomaly of oxalic acid salt metabolism, that is, a genetically determined disorder of the biochemical transformation of glycine and glyoxylic acid in the body. This is the so-called oxalosis or primary hyperoxaluria. This disease progresses and leads to the formation of oxalate stones in the bladder, as well as to diffuse deposition of calcium salts in the kidney tissue, severe chronic renal failure, vascular insufficiency (dilation of subcutaneous capillaries and blood stagnation in them), pathological fragility of bones, etc.

Oxalates in the urine of an infant may be associated with pathologies such as impaired absorption processes (malabsorption) in the small intestine, impaired absorption of bile acids from the digestive tract, congenital short small intestine or its partial atresia.

Oxalates in the urine of a child after six years of age, as well as in adolescence - oxaluria - are a consequence of the presence in the diet of a large number of products with a significant content of oxalic acid. Or for the same reasons as in adults (see - section Causes of the appearance of oxalates in urine).

What does oxalates in urine mean?

The permissible daily norm of oxalates in urine in adults (i.e. the volume of their excretion from the body) is up to 40 mg, in children of the first year of life - 1-1.3 mg. To identify oxalates in daily urine (excreted within 24 hours), laboratory studies of its physicochemical and biochemical composition are carried out to determine the density and acidity level (pH), the presence of protein, epithelial particles, erythrocytes and leukocytes, any microorganisms and, finally, crystals of salts - oxalates, urates, phosphates and salts of hippuric acid.

Urologists note that with normal urine acidity (pH> 5 and < 7, on average about 6), oxalate salts are not formed in the urine, but in acidic or alkaline urine, as well as with a sharp change in the acidity level, crystals of oxalic acid salts precipitate. And if oxalate crystals in the urine are contained in quantities significantly exceeding the physiological norms accepted in medicine, then we are talking about oxaluria.

By the way, the level of urine acidity in healthy people can change for a short time – from pH 4.5 to pH 8. This is an indicator that the kidneys are doing a good job of removing acidic metabolic products from the body and thus help maintain an optimal level of blood acidity – pH 7.35-7.4.

Decoding oxalates in urine analysis

Let's see what the decoding of oxalates in a urine test can show and what gives urologists and nephrologists grounds to draw conclusions regarding certain metabolic disorders and the presence or absence of pathologies of the kidneys and urinary system.

So, normally urine should be transparent, and when it is processed in a centrifuge, a sediment is obtained, which is studied under a microscope.

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Urate and oxalate in urine

In addition to oxalates, urates, the sodium salt of uric acid, may be present in the urine. Most often, this occurs against the background of increased acidity of urine with increased consumption of protein foods and products containing a large amount of purines (young meat, liver and other offal, brewer's yeast, porcini mushrooms, cocoa and chocolate). Urate and oxalate in the urine may appear with dehydration (after severe vomiting or diarrhea), as well as with a number of diseases, including chronic renal failure, pyelonephritis, urolithiasis, gout, tumors, leukemia.

Protein and oxalates in urine

If the analysis reveals protein and oxalates in the urine, then proteinuria (protein in the urine) may be a consequence of excessive physical exertion or significant hypothermia that preceded the analysis, as well as elevated temperature or the presence of scarlet fever, infectious hepatitis, osteomyelitis in the patient. Protein and oxalates in the urine of pregnant women are possible with nephropathy.

Oxalates and phosphates in urine

Phosphoric acid of lime, calcium or magnesium phosphate, i.e. phosphates, appear in urine with a reduced level of its acidity, which is facilitated by a diet rich in phosphorus: sea fish and seafood, milk and fermented milk products, buckwheat and oatmeal. In addition, such a test result is possible with hyperparathyroidism, diabetes, some mental illnesses, as well as leukemia. And in children under 5 years of age, oxalates and phosphates in the urine indicate not only problems with the excretion of oxalic acid salts, but also a deficiency of vitamin D ( rickets ).

Oxalates and leukocytes in urine

If, when examined under a microscope, one to five leukocytes fall into the field of view, this is considered a completely normal indicator. But if oxalates and leukocytes in the urine are elevated, this indicates either chronic pyelonephritis (inflammation of the kidneys) or such inflammatory diseases of the urinary tract as cystitis or urethritis. By the way, with these same diseases, as well as with inflammatory processes in the urethra or vagina, oxalates and mucus secreted by their mucous membranes can be found in the urine.

Causes of oxalates in urine

Now let's take a closer look at the reasons for the appearance of oxalates in urine.

In most cases, an increase in oxalates in the urine is attributed to excessive consumption of products containing oxalic acid and its compounds (sorrel, spinach, tomatoes, beets, asparagus, citrus fruits, etc.). Or oxalates in the urine of an adult are associated with pyelonephritis, diabetes mellitus, Crohn's disease, or ethylene glycol poisoning.

That is, in the latter case, a person must drink car antifreeze or brake fluid, a component of which is ethylene glycol. Indeed, when it enters the body, it decomposes with the release of oxalic acid, hence the oxalates in the urine of an adult. Now it becomes clear that oxalate stones in men's kidneys are detected by doctors twice as often as in women's...

But to explain the cause of oxalates in urine and such a serious pathology as oxalate metabolism disorder, we cannot do without physiology and biochemistry. Thus, there is a connection between the increased content of calcium oxalate in urine and diseases of the small intestine. In a number of pathologies, the process of calcium oxalate absorption in the small intestine (in the ileum) is disrupted, and then the urinary system has to work with increased load, that is, an increase in oxalates in the urine is observed.

This occurs when the obligate intraluminal microflora of the small intestine changes - a lack of anaerobic bacteria that irreversibly break down oxalic acid in the intestine - Oxalobacter formigenes. When its presence is normal, oxalates practically do not reach the kidneys and bladder. But why the population of this symbiotic bacteria in the body decreases - one can only guess.

There can be no objections regarding the abuse of products with a high content of oxalic acid. However, we must not forget that oxalic acid is also formed in the human body itself - in the small intestine: in the process of oxidation of glyoxylic acid, during the breakdown of oxaluric acid (oxalic acid monoureide), and also as a result of the oxidation of vitamin C (which is a set of derivatives of L-gulonic acid).

Are you interested in why our body needs oxalic acid? Both the oxalic acid produced by the body and more than 5% of exogenous oxalic acid (that is, entering the body with food) circulate in the blood and enter into biochemical reactions and various metabolic processes, ensuring the absorption of calcium, the stability of biological membranes, the contractile function of muscle tissue, etc.

Other reasons for the appearance of oxalates in urine include:

• in excess production of bile acids or impaired absorption of their salts in the digestive tract;
• in reducing the activity of some enzymes;
• in renal tubular acidosis;
• in calcium metabolism disorders and idiopathic hypercalciuria;
• in a deficiency of magnesium or vitamin B6 in the body;
• in excess consumption of vitamin C (more than 5 mg per day).

Treatment of oxalates in urine

How to remove oxalates from urine? Today, the most effective treatment for oxalates in urine is vitamin B6, magnesium, proper drinking regimen and, most importantly, proper nutrition.

Urologists recommend drinking at least two to two and a half liters of water per day, and also reducing the consumption of table salt (which retains fluid in the body).

In addition, having detected oxalates in the urine of an adult or oxalates in the urine of a child, doctors prescribe vitamin B6 (pyridoxine hydrochloride) and magnesium preparations, which help to establish normal excretion of oxalic acid salts from the body. For example, the drug Magne-B6 contains both vitamin B6 and magnesium. Adults should take 2 tablets three times a day (during meals, with a glass of water); children over 6 years old - one tablet three times a day. Magne-B6 is prescribed with caution in case of calcium deficiency in the body, diabetes mellitus and gastric ulcer and duodenal ulcer. In addition, it is necessary to keep in mind that magnesium reduces the absorption of iron, so it is necessary to monitor the level of hemoglobin in the blood.

To prevent calcium oxalate crystallization in urine, potassium citrate (potassium citrate) is prescribed - 10-20 mEq of potassium 3 times a day (during meals), the maximum daily dose is 100 mEq of potassium. It may also be recommended to take Asparkam (potassium and magnesium) in tablets of 0.35 g - one tablet twice a day (after meals).

How to remove oxalates from urine by increasing diuresis? Traditionally used diuretic herbs for oxalates in urine - corn silk, horsetail, knotweed, peppermint, strawberry and lingonberry leaves, field restharrow, black elder flowers - are used in the form of water infusions. Let us remind you that for 200 ml of boiling water you need to take a tablespoon of the herb and insist in a closed container for 20 minutes. This volume is designed for one day and is drunk in two or three doses.

Diet for oxalates in urine

Proper nutrition for oxalates in urine involves eliminating or maximally reducing foods with a high content of oxalic acid and its salts in the diet.

These foods include: potatoes, tomatoes and eggplants; beans and soybeans; beets, Swiss chard and celery; green peppers and chili peppers; parsley and leeks; spinach and sorrel, as well as asparagus, rhubarb and parsnips.

Oranges, apples, plums, grapes, gooseberries, raspberries, blackberries, red currants, cranberries, kiwi, persimmons, figs and dates are also rich in oxalic acid salts. Among other products in this category, nutritionists note tea, coffee, cocoa, chocolate, walnuts and pine nuts, cashews, peanuts, almonds, sesame and everyone's favorite sunflower seeds. You should not eat unripe fruits, as they contain glyoxylic acid.

The diet for oxalates in urine provides a full supply of calories and involves consuming sufficient amounts of proteins, fats and carbohydrates. So you can eat almost everything except those products that have just been listed.

What to do if you have oxalates in your urine? Be sure to see a nephrologist! Increased oxalates in your urine pose a real threat of developing calcium oxalate crystalluria, and subsequently, the formation of kidney or bladder stones.