What Are Uric Acid Stones?

Uric acid stones are formed by decreased uric acid solubility and supersaturation in the urine.

Uric acid stones

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Uric acid stones are formed by decreased uric acid solubility and supersaturation in the urine.

Uric acid is a product of oxidative decomposition of purine bases and has no physiological function in the human body. The main sources of human purines are diet, tissue breakdown and de novo synthesis. Uric acid is the end product of human purine metabolism. Under normal circumstances, it is mainly excreted by the kidney, and about 2/3 of the rest are excreted through the intestine, skin, hair, etc.

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1. Stone formation mechanism: Decreased solubility and supersaturation of uric acid in urine are prerequisites for the formation of uric acid stones. There are three main factors that cause the decline in uric acid solubility: (1) The pH of urine decreases. (2) The amount of uric acid increases. (3) decreased urine output.

2. Common causes: primary

1. Diagnosis: (1) X-ray:

1. Conservative therapy: Drugs can dissolve uric acid stones, which is an effective and inexpensive treatment method and should be listed as the first choice. Corresponding to the mechanism of uric acid formation, the conservative treatment of uric acid stones also includes 3 aspects: (1) Increase urine output. The daily urine output is generally required to be above 2000ml, which is beneficial for treatment and prevention. In fact, patients with any type of urinary tract stones should increase their urine output. Drinking orange juice is a recommended method. Studies have shown that drinking 1,200 ml of orange juice per day is equivalent to taking 60 mmol of potassium citrate, which can increase the urine pH from 5.7 to 6.5. At the same time, the citrate content in urine increased from 571 mg / d to 952 mg / d. It can prevent and cure uric acid stones and calcium-containing stones. (2) Alkaline urine. Alkaliization of urine is the most effective method of lysolysis. During the medication, urine pH should be monitored 2-3 times a day to maintain it between 6 and 6.54, and excessive alkalization should be avoided. If pH> 7.0, phosphate in the urine is easy to crystallize and precipitate, forming phosphate stones. According to estimates, when the alkalizing effect is good, the dissolution rate of pure uric acid stones can reach 1 cm / month. The methods of alkalizing urine are: Oral: Commonly used drugs are sodium bicarbonate, potassium citrate and citric acid mixture, and the dosage is determined based on the pH value of urine. Intravenous infusion method: This method dissolves stones quickly, but requires hospitalization. Commonly used drugs are sodium lactate solution and 5% sodium bicarbonate solution. It is necessary to closely observe blood pressure and other conditions during use to prevent various complications caused by water and sodium retention. The above two methods are contraindicated in those with urinary tract obstruction. Local perfusion method: suitable for patients who cannot tolerate systemic medication or who already carry urinary fistulas and catheters. Acute urinary tract infection is contraindicated. Commonly used drugs are sodium bicarbonate and trimethylolamino (THAM) methane solutions. This method dissolves the stone quickly, and the perfusion pressure should be <1.96-2.45kpa during operation.

2. Surgical treatment: Most uric acid stones can be cured by conservative treatment. Only a few uric acid stones that are large or accompanied by urinary tract obstruction or mixed with other ingredients and have poor lytic stone effect need surgical treatment. Extracorporeal shock wave lithotripsy and various in vivo lithotripsy have a good lithotripsy effect on uric acid stones. Alkaline drugs should be used before and after treatment. This is because: The alkaline environment can reduce the surface energy of stones and improve the efficiency of lithotripsy. After the stone is broken, the medicine is more likely to work. Small stones may remain after rubble. Uric acid stones generally do not require open surgery. (3) Reduce uric acid, including reducing intake of high-purine foods, taking allopurinol, and prohibiting drinking. Allopurinol can significantly reduce uric acid levels in hematuria. The drug can cause rash, fever, acute gout, etc. Long-term application can increase the content of xanthine and hypoxanthine in the body, and there may be stones of corresponding components. The usual dose is 300mg / d, and it can be taken in divided or one-time administration.

3. Prevention: (1) General prevention: It can increase urine output, control diet, and reduce intake of high-protein and high-purine foods. This also has a preventive effect on calcium oxalate stones. (2) Specific prevention: Patients with gout should use alkaline drugs to maintain urine pH between 6 and 6.5 regardless of whether uric acid is increased in hematuria to prevent stone formation. If the amount of uric acid excreted in 24 hours is> 750mg, it is not suitable to use uric acid drugs to prevent the uric acid concentration in urine from being too high. Studies have shown that allopurinol prevents uric acid stones in patients with hyperuricemia and hyperuricemia. However, for patients with simple mild elevated blood uric acid and no gout symptoms, prophylactic allopurinol is generally not recommended. Only general prevention is sufficient. Tumor patients undergoing radiotherapy and chemotherapy can easily form uric acid stones and should be given preventive treatment. The method is to start allopurinol a few days before radiotherapy or chemotherapy to avoid gout and uric acid stone formation.