**1. Introduction**

The high rate of recurrence of urinary‐stone disease indicates the necessity of metaphylaxis, especially in children. All lifestyle changes and medications for prevention of stone disease define the stone metaphylaxis. After stone treatment, even stone‐free children showed a 25% recurrence rate during a three‐year follow up [1]. In addition, after the urinary tract stone surgery, the rate of stone recurrence over five years has been observed to vary from 38 to 65% depending on the malformation of the urogenital system [2]. Children with metabolic disorders had a higher recurrence rate, so metabolic examination is essential to preventive treatment in children. In the pediatric age group, the most common metabolic disorders are hypercalciuria and hypocitraturia, with hypercalciuria more often found in the endemic areas and hypocitraturia in the nonendemıc areas [3, 4]. Metaphylaxis has been found to reduce recurrence rates by about half, even in recurrent kidney stones [5].

Proper metaphylaxis must be preceded by a complete metabolic evaluation. In addition, identification of any anatomical abnormalities that may increase the risk of nephrolithiasis, a detailed dietary history, patient and family medical history, and a record of any medications used must be obtained [6].

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The European Association of Urology (EAU) guidelines recommend metabolic assessment based on the type of the stones, which may be obtained spontaneously or after pediatric uro‐ lithiasis treatment [6]. However, it is not always possible to obtain stones with minimally invasive surgery, particularly in patients undergoing retrograde intrarenal surgery and shock wave lithotripsy (SWL). In this case, a general screening is required. The EAU's pediatric urology guidelines recommend biochemical testing, including serum urea, creatinine, elec‐ trolytes, phosphorus, alkaline phosphate, uric acid, total protein, and albumin. If hypercalce‐ mia is identified, the level of parathormone should be measured [6]. The ratio of spot urine calcium to creatinine should be analyzed, including a urinalysis and urine culture. Calcium, phosphate, magnesium, oxalate, uric acid, citrate, cysteine, protein, and creatinine clearance must be measured in a 24‐hour urine [6]. In some cases, the test can be customized based on the stone type.

Renal tubular acidosis (RTA) should be suspected in calcium stones with urine pH that repeat‐ edly tests higher than 5.5 [7]. In such patients, blood‐gas levels must be analyzed. A urine pH consistently testing lower than 6 may indicate an acidic arrest [7].

Any renal anomaly responsible for the stones should be treated if there is a treatable pathol‐ ogy, including ureteropelvic junction obstruction. The child's diet must be reviewed for risk factors, including anorexia, high salt intake, and excessive sugar intake. Metaphylaxis must take into consideration medically necessary diets, including ketogenic diets.

Urolithiasis of 1–2% is associated with use of some medications [8]. Detecting such risks in the medical history is important for proper treatment planning. Vitamins C and D, loop diuretics, carbonic anhydrase inhibitors, and laxatives affect the metabolism and may lead to stone for‐ mation. The mechanisms by which these drugs potentiate stone formation and the treatment approaches pertinent to them will be discussed later in this chapter [8]. Magnesium trisili‐ cate, commonly used for gastroesophageal reflux, causes silica stones, and ciprofloxacin, sul‐ fonamide, triamterene, indinavir, and ceftriaxone form stones [8–10] that are radiolucent or semiopaque [8]. Stones that are weakly opaque or nonopaque and for which analysis results cannot be obtained should be suspected as drug‐induced calculi.

Excessive use of laxatives causes formation of ammonium acid urate stones. Low urine vol‐ ume and the low pH associated with chronic diarrhea increase the ammonium in urine [8]. In addition, anorexia, which is usually a postpuberty disease, is a cause of urolithiasis, with 5% of anorexia patients forming kidney stones [11], which are usually calcium oxalate, but which may be ammonium urate [12, 13]. The latter being stones that develop in cases of decreased urinary output, increased urine ammonium with hypophosphaturia, and the hyperchloremic acidosis associated with diarrhea [14]. Anorexia and any other identified primary disease should be treated before metaphylaxis.

Loop diuretics are commonly used to treat pulmonary disorders in newborns and act on the Na+ ‐K+ ‐2Cl pump through the thick part of Henle's loop, inhibiting the reabsorption of magnesium and calcium with the reabsorption of sodium [15]. In infants, due to their low glo‐ merular filtration rates and immature hepatic development, the half‐life of drugs is 6–20‐fold longer, the clearance is 1.2–1.4‐fold lower, and volume distribution is 1.3–6‐fold broader than in adults [15]. In addition, the half‐life is further increased in premature infants, with a half‐ life that is 6 hours in term infants and as long as 67 hours in premature infants [16]. However, increased knowledge of the pharmacokinetics and complications of using loop diuretics in infants have decreased the incidence of stones associated with these drugs [17, 18].
