Prevention of urinary stones
Urinary stones are a common disease that is not only highly prevalent, but also good and easy to recur, which is why we often get inquiries from patients and friends about prevention of urinary stones. At present, folklore and the Internet are also full of various claims that are difficult to distinguish from the truth, causing confusion to many people. In order to give you a professional and reliable advice, according to the most professional and authoritative “China Urological Diseases Diagnosis and Treatment Guide”, I have selected a small amount of chapters about urinary tract stone prevention for the reference of concerned friends. There are many types of stones, and it is best to do a stone composition analysis first for any stone prevention, so that the prevention will be more targeted.
1. Prevention of calcium-containing urinary stones Since there is still some controversy about various therapeutic measures to prevent the recurrence of calcium-containing stones and, moreover, patients often need to receive treatment for a long time or even for life, it is of utmost importance to fully understand the pros and cons of various preventive measures. For any preventive measure, not only does it need to be clinically effective, but it also needs to be easy to implement and free of side effects. Otherwise, it will be difficult for patients to comply with treatment.
Preventive measures for patients with calcium-containing urinary tract stones should start with lifestyle changes and dietary modification. Maintaining an appropriate body mass index, appropriate physical activity, nutritional balance and increased intake of citric acid-rich fruits are important measures to prevent stone recurrence. Only when changing lifestyle habits and adjusting dietary structure are ineffective, medication will be considered.
(1) Increase fluid intake: Increasing fluid intake increases urine output, thereby reducing the supersaturation of urinary stone components and preventing stone recurrence. The recommended daily fluid intake is 2.5 to 3.0 L or more to keep the daily urine volume above 2.0 to 2.5 L. It is recommended that patients with urolithiasis measure their own urine specific gravity at home so that a specific gravity of less than 1.010 is appropriate to achieve and maintain a reliable dilution of urine.
Regarding the type of water to drink, non-dairy fluids with low oxalic acid content are generally considered to be appropriate. There are still differing opinions on whether hard water consumption increases the formation of calcium-containing stones. Excessive consumption of caffeine, black tea, grape juice, apple juice, and Coca-Cola should be avoided. Orange juice, cranberry juice and lemonade are recommended.
(2) Dietary modifications: Maintain a comprehensive nutritional balance in the diet, emphasizing the avoidance of excessive intake of one of the nutrients.
1) Dietary calcium: Dietary calcium levels below 800 mg (20 mmol/d) can cause a negative calcium balance in the body. Although a low calcium diet can reduce urinary calcium excretion, it may lead to osteoporosis and increased urinary oxalic acid excretion. A diet with a normal calcium content and a restricted intake of animal protein and sodium has a better effect on preventing stone recurrence than a conventional low-calcium diet. Diets with normal ranges or appropriate levels of high calcium are clinically valuable in preventing recurrence of urinary calcium-containing stones. However, calcium supplementation other than dietary calcium may be detrimental to stone prevention because an uncontrolled high-calcium diet can increase urinary supersaturation levels. Prevention of recurrence of calcium-containing stones by pharmacologic calcium supplementation is indicated only for enterogenic hyperoxaluria, where oral administration of 200 to 400 mg of calcium citrate increases urinary citrate excretion while inhibiting urinary oxalate excretion.
It is recommended to consume more dairy products (milk, cheese, yogurt, etc.), tofu and small fish. The daily intake of calcium for adults should be 800 to 1000 mg (20 to 25 mmol).
A low-calcium diet is recommended for patients with absorptive hypercalciuria and a calcium-restricted diet is not recommended for other patients.
2) Limit dietary oxalic acid intake: Although only 10%-15% of urinary oxalic acid is of dietary origin, urinary excretion of oxalic acid increases significantly with high intake of oxalic acid-rich foods. Patients with calcium oxalate stones, especially those with hyperoxaluria, should avoid foods rich in oxalic acid such as kale, almonds, peanuts, beets, parsley, spinach, rhubarb, black tea, and cocoa powder. Among them, spinach has the highest oxalic acid content, and patients with calcium oxalate stones should be more careful to avoid spinach.
A low-calcium diet promotes the absorption of oxalate in the intestine and increases urinary oxalate excretion. Calcium supplementation is beneficial in reducing intestinal oxalate absorption, however, only in patients with intestinal-derived hyperoxaluria.
3) Limit sodium intake: A high sodium diet increases urinary calcium excretion and sodium intake should be less than 2g per day.
4) Limit excessive protein intake: A low-carbohydrate and high animal protein diet is associated with the formation of calcium-containing stones. A high protein diet causes an increase in urinary calcium and urinary oxalate excretion while decreasing urinary citrate excretion and lowering urinary pH, which is one of the important risk factors for the formation of calcium-containing stones in the urinary tract.
It is recommended to consume a nutritionally balanced diet, and it is important to maintain a balanced diet of 3 meals: breakfast, lunch and dinner. Avoid excessive intake of animal protein, which should be limited to 150g per day. In particular, patients with recurrent stones should not consume more than 80 g of protein per day.
5) Weight loss: Studies have shown that being overweight is a crucial factor in the formation of urinary stones. It is recommended to maintain a body mass index (BMI) between 11 and 18 for patients with urinary stones.
6) Increase the intake of fruits and vegetables: The intake of fruits and vegetables in the diet dilutes the risk factors for stone formation in the urine, but does not affect the concentration of urinary potassium and urinary citrate. Therefore, increasing the intake of fruits and vegetables can prevent stone recurrence in patients with hypocitraturia.
7) Increase the intake of coarse grains and fiber: Rice bran can reduce urinary calcium excretion and decrease the recurrence of urinary stones, but avoid oxalic acid-rich fiber foods such as wheat bran.
8) Reduce vitamin C intake: Vitamin C is naturally transformed to produce oxalic acid. The excretion of urinary oxalic acid increases significantly with vitamin C, and the risk of calcium oxalate crystals increases accordingly. Although there is no data linking high dose vitamin C intake to recurrence of calcium oxalate stones, patients with recurrent calcium oxalate stones are advised to avoid high doses of vitamin C. It is recommended that their daily vitamin C intake should not exceed 1.0 g.
9) Restriction of high purine diet: Patients with calcium oxalate stones with hyperuricemia should avoid a high purine diet, with a recommended daily intake of less than 500 mg of purine in food. Foods rich in purine include: animal offal (liver and kidney), poultry skin, herring with skin, sardines, anchovies, etc.
(3) Prophylaxis: Although there are many types of drugs used for the prophylaxis of calcium-containing stones, only alkaline citrate, thiazide diuretics and allopurinol are currently used with more certain efficacy. For Chinese herbs, which are of great concern to the Chinese people, herbs that are considered to have some preventive effect on calcium-containing stones include zedoary, fatty sea, money grass, cornus and plantain core. However, there is a lack of reports on clinical efficacy.
2, prevention of uric acid stones The key to prevent uric acid stones is to increase urine volume, improve the pH of urine and reduce the formation and excretion of uric acid in three aspects.
(1) Drink plenty of water: keep the daily urine volume above 2000 ml.
(2) Alkalinize urine: Keep the pH of urine between 6.5 and 6.8. You can give sodium potassium hydrogen citrate (Yolite) 1 to 2 g , 3 times/d, potassium citrate 2 to 3 g or sodium potassium citrate 3 to 6 g, 2 to 3 times/d, or sodium bicarbonate 1.0 g, 3 times/d.
(3) Reduction of uric acid formation: For increased blood uric acid or uric acid, oral allopurinol 300 mg/d. Folic acid can inhibit xanthine oxidase activity more effectively than allopurinol, and oral folic acid 5 mg/d is recommended.
3. Prevention of infected stones Low calcium and low phosphorus diet is recommended. Aluminum hydroxide or aluminum carbonate gel can combine with phosphorus ions in the small intestine to form insoluble aluminum phosphate, thus reducing intestinal absorption of phosphorus and excretion of urinary phosphorus.
For amyl phosphate and carbonate apatite stones caused by bacterial infection with urease, the stones should be removed surgically if possible.
The use of antibiotics based on drug sensitivity testing is recommended for the treatment of infections. It is emphasized that anti-infective therapy requires an adequate course of medication. In the initial phase of antibiotic therapy, the dose of antibiotics is relatively high (therapeutic dose), and the urine is made sterile by 1 to 2 weeks of treatment, after which the drug dose can be halved (maintenance dose) and maintained for 3 months. Attention should be paid to monthly bacterial cultures, and if bacteria are found again or if the patient has symptoms of urinary tract infection, the drug should be restored to the therapeutic dose to better control the infection.
Acidification of urine can improve the solubility of phosphate and can be done with amyl chloride 1g, 2-3 times/d or methionine 500mg, 2-3 times/d.
Urease inhibitors should be used in patients with severe infections. Acetohydroxamic acid and hydroxyurea are recommended. The first dose of acetohydroxamic acid is recommended to be 250 mg twice a day for 3 to 4 weeks, and the dose can be increased by 250 mg three times a day if the patient can tolerate it.
4. Prevention of cystine stones Pay attention to drink a lot of water to increase the solubility of cystine and ensure that the daily urine volume is above 3000 ml, i.e., drink at least 150 ml/h.
Alkalinize the urine so that the pH of the urine reaches 7.5 or more. You can take sodium potassium hydrogen citrate (Youlert) 1 to 2 g, 3 times/d.
It is advisable to consume a low-protein diet based on vegetables and cereals, and avoid excessive consumption of methionine-rich foods (soy, wheat, fish, meat, beans and mushrooms, etc.), as a low-protein diet can reduce the excretion of cystine.
Limit sodium intake to less than 2g/d.
If urinary cystine excretion is higher than 3 mmol/24h, apply thiopronine (-mercaptopropionylglycine) 250-2000 mg/d or captopril 75-150 mg/d.
5. Prevention of other rare stones
(1) Prevention of drug stones
1) Prevention of calcium-containing drug stones: stones caused by calcium supplementation and Vit D supplementation are associated with increased excretion of urinary calcium, and supplementation with high doses of Vit C may promote excretion of urinary oxalic acid. Therefore, prevention of stones from calcium-containing drugs focuses on reducing urinary calcium and urinary oxalate excretion and decreasing urinary calcium salt and oxalate saturation.
2) Prevention of non-calcium-containing drug stones: The best way to prevent indinavir stones is to drink enough water, with a daily intake of 3000 ml or more, to prevent the precipitation of drug crystals. Acidifying the urine so that the urine pH is below 5.5 may facilitate the dissolution of drug crystals.
The prevention of aminoglutethimide, acetazolamide and sulfonamide stones is to drink plenty of water to dilute the urine and apply alkaline drugs appropriately to raise the pH of the urine, thus increasing the dissolution of drug crystals.
(2) Prevention of purine stones: Purine stones (mainly including 2,8-dihydroxyadenine stones and xanthine stones) should be prevented by adopting a low purine diet; allopurinol can inhibit xanthine oxidase, which can reduce the excretion of 2,8-dihydroxyadenine and thus play a role in preventing the occurrence of stones. Theoretically, alkalinization of urine can promote the dissolution of 2,8-dihydroxyadenine stones. However, attempts to raise the urine pH above 9.0 through drugs are extremely difficult clinically. Therefore, the practical application of alkalinizing urine is not of great value.