Uric acid in the urine

Uric acid excreted in urine reflects the intake of purines with food and the breakdown of endogenous purine nucleotides. Approximately 70% of the total uric acid in the body is excreted in the urine. The uric acid clearance is 10% of the filtered amount. Renal excretion of uric acid is a derivative of a filtered amount that is almost completely reabsorbed in the proximal tubule, as well as secretion and reabsorption in the distal tubule.

Determination of uric acid in urine should be carried out together with its determination in the blood. This allows in many cases to establish the pathological mechanism underlying the gout in the patient (excessive production of uric acid in the body or a violation of its excretion). A sign of hyperproduction of uric acid in the body is considered to be urinary excretion of more than 800 mg / day in the case of a study without restriction in the diet or 600 mg / day with malopurin diet. Before the study, you should make sure of the normal function of the kidneys (in the case of decreased creatinine clearance, a decrease in the excretion of uric acid does not exclude its hyperproduction), and also to exclude possible effects of the drugs on urate excretion. If there is a disruption of excretion, a high concentration of uric acid in the blood is not accompanied by an increase in its content in the urine.

Reference values (norm) of uric acid in the urine

	The content of uric acid
Type of diet	Mg / day	Mmol / day
Normal diet	250-750	1.48-4.43
Non-purulent diet:
Men	Up to 420	Up to 2.48
Women	Up to 400	Up to 2.36
Diet with low purine content:
Men	Up to 480	Up to 2.83
Women	Up to 400	Up to 2.36
Diet with a high content of purines	Up to 1000	Until 5.90

The definition of the mechanism of development of gout helps the clinician and in the choice of the scheme of treatment of the patient. With increased production of uric acid, inhibitors of xanthine oxidase, an enzyme that plays a key role in the formation of uric acid in the body, are prescribed. The dose of the drug (allopurinol) should be selected in such a way that the decrease in uricemia is not more than 35.7-47.6 μmol / l. If uric acid is disrupted, a dose of uricosuric drugs blocking the tubular reabsorption of uric acid in the kidneys is prescribed or increased, or these drugs are used in combination with dietotherapy. When appointing uricosuric drugs, it should be remembered that increased uric acid excretion increases the risk of urate stones formation, which can be reduced by the appointment of abundant drinking.

In the first months (1-4 months) of gout therapy, the main criterion of effectiveness is the achievement of serum uric acid concentrations in men below 0.36 mmol / L (ideally 0.24-0.30 mmol / L), in women below 0.3 mmol / l. If the concentration of uric acid does not decrease below 0.4 mmol / l, dissolution of urate in the extracellular fluid and tissues does not occur and there is a danger of gout progression.