I. Background
Urolithiasis is one of the common diseases in urology and ranks first among urological inpatients. Epidemiological data from European and American countries show that 5-10% of people have urinary stones at least once in their lifetime, and the annual incidence of new urinary stones in Europe is about 100-400/100,000 people. The incidence of urinary stones in China is 1%~5%, and as high as 5%~10% in the south; the annual new incidence rate is about 150~200/100,000 people, of which 25% of patients need hospitalization. In recent years, the incidence of urinary stones in China has increased, and it is one of the 3 major areas in the world with high incidence of stones.
Second, the classification of urinary stones
According to the etiology, urinary stones are divided into metabolic stones, infectious stones, drug stones and idiopathic stones; according to the crystal composition, they are divided into calcium-containing stones and non-calcium-containing stones; according to the location, they are divided into kidney stones, ureteral stones, bladder stones and urethral stones; according to X-rays, they are divided into positive stones that do not penetrate X-rays and negative stones that penetrate X-rays.
Risk factors of urinary tract stone formation
There are many factors affecting stone formation, age, gender, race, heredity, environmental factors, diet and occupation have a great influence on stone formation. Metabolic abnormalities in the body, obstruction of the urinary tract, infection, foreign body and drug use are common causes of stone formation. Attention to these issues can reduce stone formation and recurrence.
(i) Metabolic abnormalities: urine acidity, hypercalcemia, hypercalciuria, hyperoxaluria, hyperuricuria, cystinuria, hypocitraturia, and hypomagnesuria can induce urinary stones.
(ii) Local etiology: urinary tract obstruction, infection and the presence of foreign bodies in the urinary tract are the main local factors that induce stone formation. Obstruction can lead to infection and stone formation, while stones themselves are also foreign bodies in the urinary tract, and the latter can aggravate the degree of obstruction and infection.
(C) Drug-related factors: Drug-induced kidney stones account for 1%-2% of all stones and are divided into 2 major categories: one is drugs with high concentration and relatively low solubility in urine, such as sulfonamides and aminoglutethimide, which are themselves components of stones. The other category is drugs that can induce stone formation, such as VitD, VitC, and corticosteroids, etc. These drugs lead to the formation of other components of stones in the process of metabolism.
IV. Treatment of urinary stones
In recent years, with the in-depth research on the etiology of urinary stones, the metabolic risk factors of stones have become more and more important to urologists. Extracorporeal shock wave lithotripsy, percutaneous nephrolithotomy, ureterorenoscopy and laparoscopic lithotripsy have emerged one after another, making the treatment of urinary stones gradually develop in the direction of minimally invasive.
V. Prevention of urinary stones
(A) Prevention of calcium-containing urinary tract stones
Since there is still some controversy about various therapeutic measures to prevent the recurrence of calcium-containing stones, and patients often need to receive treatment for a long time or even for life, it is most important 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 stones should start with lifestyle changes and dietary modification. Maintaining a proper weight, 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 can increase urine volume, thus reducing the supersaturation of urinary tract stone components and preventing stone recurrence. The recommended daily fluid intake is 2.5~3.0L or more. 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 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. Drinking more orange juice and lemon water is recommended.
2, diet regulation: maintain a comprehensive balance of dietary nutrition, emphasizing avoidance of excessive intake of one of these nutrients.
(1) Dietary calcium content: consuming a diet with normal calcium content and limiting the intake of animal protein and sodium has a better effect on preventing stone recurrence than a traditional low-calcium diet. Foods such as dairy products (milk, cheese, yogurt, etc.), tofu and small fish are recommended to be consumed more frequently. The daily calcium intake for adults should be 800~1000mg (20~25mmol). A low-calcium diet is recommended for patients with absorptive hypercalciuria and is not recommended for other patients.
(2) Restrict the intake of oxalic acid in the diet: Although only 10-15% of urinary oxalic acid is derived from the diet, the excretion of oxalic acid in the urine will increase significantly after a large 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, the content of oxalic acid in spinach is the highest, and patients with calcium oxalate stones should pay more attention to avoid eating spinach.
(3) Limit the intake of sodium: high sodium diet will increase the excretion of urinary calcium, the daily sodium intake should be less than 2g.
(4) Limit excessive protein intake: A high protein diet causes increased 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 urinary calcium-containing stones. 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. Among them, patients with recurrent stones should not consume more than 80g of protein per day.
(5) Reduce body weight: Studies have shown that being overweight is a crucial factor in urinary tract formation.
(6) Increase the intake of fruits and vegetables: Increasing the intake of fruits and vegetables can prevent stone recurrence in patients with hypocitraturia.
(7) Increase coarse grains and fiber diet: 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 the intake of vitamin C.
(9) Restrict high purine diet: foods rich in purines are: animal offal (liver and kidney), poultry skin, herring with skin, sardines, anchovies, etc.
3, drug prophylaxis: Although there are many kinds of drugs used for the prophylaxis of calcium-containing stones, only alkaline citrate (such as sodium potassium hydrogen citrate, i.e., Youlet), thiazide diuretics (such as hydrochlorothiazide and indapamide, etc.) and allopurinol are currently used with more certain efficacy.
(B) Prevention of uric acid stones
The key to the prevention of uric acid stones is to increase urine volume, improve the pH value of urine and reduce the formation and excretion of uric acid in 3 ways.
1. Drink a lot of water: keep the daily urine volume above 2000ml.
2.Alkalinize urine: to keep the PH value of urine between 6.5~6.8, you can give 1~2g of sodium potassium hydrogen citrate (Youlait), 3 times/day.
3. Reduce the formation of uric acid: For increased blood uric acid or uric acid, take 300mg/d of allopurinol orally. folic acid can inhibit xanthine oxidase activity more effectively than allopurinol, and 5mg/d of folic acid orally is recommended.
(C) 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 for the treatment of infections based on drug sensitivity tests is recommended. The need for an adequate course of anti-infective therapy is emphasized.
(iv) Prevention of cystine stones
Drink plenty of water to increase the solubility of cystine, ensure that the daily urine volume is above 3000 ml, i.e., drink at least 150 ml/h. Alkalize the urine so that the pH value of urine reaches above 7.5, you can take 1-2 g of sodium potassium hydrogen citrate (Youlert) 3 times/day. 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.). A low-protein diet can reduce the excretion of cystine.
(E) Prevention of other rare stones
1. Prevention of drug stones
(1) Prevention of calcium-containing drug stones: prevention of calcium-containing drug stones is mainly to reduce urinary calcium and urinary oxalic acid excretion, and to reduce the saturation of urinary calcium salts and oxalate.
(2) Prevention of non-calcium-containing drug stones: The best way to prevent them is to drink enough water, with a daily intake of 3000 ml or more, to prevent the precipitation of drug crystals. Acidification of urine so that the urine PH value is below 5.5 can facilitate the dissolution of drug crystals.
2, purine stone prevention: purine stone prevention should be taken on a low purine diet; allopurinol can inhibit xanthine oxidase, thus playing a role in preventing the occurrence of stones.