Generality
Uricemia is a laboratory parameter that expresses the amount of uric acid present in the blood.
Purines (adenine and guanine) are nitrogenous bases, which constitute the DNA present in the nucleus of animal and plant cells.
Since our body is composed of an extremely high number of cells, which are continuously renewed, most of the purines come from the endogenous synthesis, while only a minimal percentage derives from the foods introduced with the diet.
Uric acid circulates in the blood partly free and partly linked to transport proteins. The organ responsible for its removal is the kidney, which eliminates about 450 mg every day with urine and another 200 mg through digestive secretions.
Hyperuricemia occurs due to excess production and / or to the difficult renal elimination of uric acid.
What's this
The uricemia is the measure of the amount of uric acid present in the circulation.
Uric acid is a waste substance of cell metabolism, produced following the degradation of purines. Its concentration in the blood is the result of the balance between its production by the body and its elimination with urine.
If uric acid is produced in excess or is not sufficiently eliminated, it can accumulate in the body and cause an increase in its blood levels ( hyperuricemia ).
The uric acid test is used to detect high levels of this compound and help the doctor diagnose gout . This analysis is also used to monitor uric acid levels over time during certain therapies and as an aid in the diagnosis of the causes that cause the recurrent formation of kidney stones.
Why do you measure
Blood uric acid testing is required when the doctor suspects the presence of high levels of uricemia or believes that joint pain or other symptoms may be due to gout.
The uricemia is measured by:
- Detect high levels of uric acid in the blood;
- Monitor uric acid levels when undergoing certain chemotherapy or radiotherapy treatments;
- Check gout patients, who are at risk of developing kidney stones.
Normal values
The normal values of uric acid in the blood range from 4 to 8 mg / dl.
A hyperuricemic person is defined as the subject who has a uricemia greater than 7 mg / dl if man and 6.5 mg / dl if a woman, after 5 days of hypopuric diet and without taking drugs that affect uricemia.
Uricemia Alta - Causes
Uric acid levels can be high due to:
- Reduced renal excretion : it is certainly the most common cause of hyperuricemia; it can be hereditary or develop in patients on diuretic therapy or with pathologies that reduce the glomerular filtration rate. Ethanol induces an increase in purine catabolism in the liver and the formation of lactic acid, which blocks the excretion of uric acid from the renal tubules. Lead poisoning and cyclosporine (usually used in transplant patients) irreversibly damage the renal tubules, leading to the retention of uric acid.
- Increased production : it can derive from high nucleoprotein turnover in haematological diseases (eg lymphoma, leukemia and haemolytic anemia) and from those situations in which there is a high index of proliferation and cell death (eg psoriasis, cytotoxic chemotherapy and radiotherapy) . This situation can also be seen as a hereditary primary alteration and in obesity (uric acid production being correlated with the body surface).
- Increased purine intake : it depends on the excessive intake of foods rich in purines (eg liver, kidney, anchovies, asparagus, broth, herring, meat and broth sauces, mushrooms, mussels, sardines, sweetbreads, etc.).
In many cases, the cause of excess uric acid remains unknown.
High uricemia can lead to the formation of so-called "gouty tophi" at the level of the joints, up to obvious situations of gout . This latter condition is characterized by inflammation in the joints, secondary to the precipitation of uric acid in the form of needle-like crystals of monosodium urate.
The greater the level and duration of hyperuricemia, the greater the probability of developing gout, and the more serious the symptoms.
When it accumulates in the urine without being able to dissolve, then, uric acid remains in the urinary tract. Here it can precipitate in the form of small flattened or sometimes irregular crystals, which can be aggregated to form grains or calculations.
These elements can cause obstructive uropathy .
Hyperuricemia - Main causes
The causes of uricemia or high uric acid may be different and include:
- Diet rich in food of animal origin (red meat, game and offal);
- Pathologies affecting the kidneys (renal insufficiency, calculi and polycystic kidney);
- Chemotherapy treatments based on cytotoxic drugs or radiotherapy;
- Metastatic cancer;
- Multiple myeloma;
- Leukemia;
- Osteoarticular pathologies;
- Alcoholism;
- Glucose-6-phosphate dehydrogenase deficiency (hereditary enzymatic defect that affects red blood cells making them more sensitive to damage caused by oxidation);
- Gout;
- Lead poisoning;
- Obesity;
- Metabolic syndrome;
- Prolonged use of diuretics and other drugs such as levodopa, pyrazinamide and ethambutol.
Consequences of hyperuricemia: gout
Gout is a typical disease attributable to the increase in uricemic rate, consequent to the precipitation of crystals of uric acid in the joints and in the connective tissue. The low solubility of uric acid and its tendency to precipitate in microcrystalline form are aggravated by hyperuricemia, cold and acidosis.
If uric acid crystals fall into the urine in the kidney basin, hyperuricemia leads to the formation of kidney stones.
Hyperuricemia can also be the consequence of serious diseases, such as leukemia, lymphoma and extensive burns.
The role of the diet is marginal, even if in the presence of hyperuricemia it is advisable to re-evaluate eating habits before resorting to specific drugs.
Low Uricemia - Causes
A decrease in uricemia may depend on impaired kidney function, but may also result from a viral hepatitis or simply from a diet low in foods rich in purines (such as meat).
Hypouricemia, or the low concentration of uric acid in the blood, is also found in Wilson's disease (hereditary metabolic defect) and in some blood disorders.
Low values may be associated with certain types of liver disease, Fanconi syndrome or exposure to toxic substances.
The values of uricemia decrease during therapies with probenecid, sulfinpyrazone, allopurinol, ACTH and cortisone, dicumarolics, estrogens and salicylates at high doses.
Hypouricemia - Main causes
Low uricemia can be determined by:
- Lactic acidosis, a metabolic decompensation that causes an accumulation of acids in tissues and body fluids;
- Anemia;
- Some forms of cancer;
- Fasting and poor intake of animal proteins and purines;
- Liver diseases, in particular viral hepatitis;
- Nephropathies, or any pathological process affecting the kidney, such as Fanconi syndrome;
- Cortisone, estrogen and salicylate based therapies;
- Pregnancy.
How to measure it
The dosage of uricemia occurs after blood is drawn from a vein in the forearm. If necessary, the person must carry a container with the urine collected within 24 hours, in order to be able to evaluate the uricosuria, that is the evaluation of the quantity of uric acid present in the urine.
Preparation
The uricemia dosage requires that the patient is fasting for at least 8-10 hours before taking, but it is possible to drink small amounts of water. Before the exam, it is advisable to remain upright for at least 30 minutes.
Interpretation of Results
Uricemia Alta
Hyperuricemia can be caused by an increase in the production of uric acid by the body and / or by the inability of the kidneys to eliminate it sufficiently. Increased production can be caused by an increase in cell death (as happens when you are undergoing certain treatments for cancer treatment) or in the presence of an inherited tendency to over-produce uric acid.
Reduced uric acid excretion is the result of impaired renal function.
Metastatic cancer, multiple myeloma and leukemias can increase uric acid production. Chronic kidney diseases, acidosis, toxemia of pregnancy and alcoholism can lead to decreased excretion.
An increase in blood uricemia may also be due to the diet particularly rich in red meat, game and offal.
There are also some congenital genetic defects that affect the metabolism of purines. In many cases, the cause of excess uric acid remains unknown.
Uric acid concentrations higher than normal can cause the formation of crystals in the joints, which can then lead to inflammation of the joints, and to the pain typical of gout. Uric acid can also form stones that can damage the kidneys.
Low Uricemia
Low levels of uricemia are found less often than at high levels and are rarely considered a cause for concern. Low blood uric acid values may be associated with certain types of liver or kidney disease, Fanconi syndrome, exposure to toxic substances and Wilson's disease.
