genitourinary disorders
Urinary Calculi
Prevention of Urinary Calculi
In a patient who has passed a first calcium calculus, the likelihood of forming a 2nd calculus is about 15% at 1 year, 40% at 5 years, and 80% at 10 years. Drinking large amounts of fluids—8 to 10 ten-ounce (300-milliliter) glasses a day—is recommended for prevention of all stones. Patients who form stones (those with a history of recurrent stones and those with stones newly diagnosed via imaging) should drink enough fluid to produce at least 2.5 liters of urine daily. Recovery and analysis of the calculus, measurement of calculus-forming substances in the urine, and the clinical history are needed to plan other prophylactic measures. In<3% of patients, no metabolic abnormality is found. These patients seemingly cannot tolerate normal amounts of calculus-forming salts in their urine without crystallization. Thiazide diuretics,potassium citrate, and increased fluid intake may reduce their calculus production rate. is recommended to prevent Hypokalemia . Restriction of dietary animal protein is also recommended ( For patients withhypocitruria,potassium citrate(20 mEq [20 mmol/L] orally twice a day) enhances citrate excretion. A normal calcium intake (eg, 1000 mg or about 2 to 3 dairy servings per day) is recommended, and calcium restriction is avoided. Oral orthophosphate has not been thoroughly studied. Alternative alkaline agents (eg, sodium orpotassium bicarbonate) can be used to enhance citrate excretion ifpotassium citratecannot be tolerated. Hyperoxaluriaprevention varies. Patients with small-bowel disease can be treated with a combination of high fluid intake, calcium loading (usually in the form ofcalcium citrate400 mg orally twice a day with meals),cholestyramine, and a low-oxalate, low-fat diet. Hyperoxaluria may respond topyridoxine100 to 200 mg orally once a day, possibly by increasing transaminase activity, because this activity is responsible for the conversion of glyoxylate, the immediate oxalate precursor, toglycine. Inhyperuricosuria,intake of animal protein should be reduced. If the diet cannot be changed,allopurinol300 mg each morning lowers uric acid production. For uric acid calculi, the urine pH must be increased to between 6 and 6.5 by giving an oral alkalinizing medication that contains potassium (eg,potassium citrate20 mEq [20 mmol/L] twice a day) along with increased fluid intake. Infection withurea-splitting bacteriarequires culture-specific antibiotics and complete removal of all calculi. If eradication of infection is impossible, long-term suppressive therapy (eg, withnitrofurantoin) may be necessary. In addition,acetohydroxamic acidcan be used to reduce the recurrence of struvite calculi. To prevent recurrentcystine calculi,urinary cystine levels must be reduced to<250 mg cystine/L of urine. Any combination of increasing urine volume along with reducing cystine excretion (eg, withalpha-mercaptopropionylglycine [tiopronin] orpenicillamine) should reduce the urinary cystine concentration. 1.Ferraro PM, Bargagli M, Trinchieri A, et al: Risk of kidney stones: Influence of dietary factors, dietary patterns, and vegetarian–vegan diets.Nutrients12(3): 779, 2020. doi: 10.3390/nu12030779 