I. What are the common causes? There are many factors that affect the formation of stones, including age, gender, race, genetics, environmental factors, and dietary habits. Metabolic abnormalities, congenital urinary tract malformations, infections, foreign bodies, drugs and certain special exogenous substances are the common causes of stone formation. (i) Metabolic abnormalities Mainly include: urinary acidity, hypercalcemia, hypercalciuria, hyperoxaluria, hyperuricuria, cystinuria, hypocitraturia, hypomagnesuria. (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 obstruction and infection. Clinical obstructive diseases that predispose to urinary tract stone formation include two major categories: mechanical and dynamic obstruction. Among them, pelvic ureteral junction stenosis, bladder neck stenosis, spongy kidney, renal ureteral malformation, ureteral orifice bulge, renal cyst, renal calyx diverticulum and horseshoe kidney are the common mechanical obstructive diseases. In addition, intrarenal-type pelvic and calyx neck stenosis can cause urinary retention, which can induce the formation of kidney stones. Neurogenic bladder and congenital giant ureter are dynamic obstructive disorders, and the latter two can also cause urinary retention and promote stone formation. (iii) Drug-related factors Drug-induced kidney stones account for 1% to 2% of all stones and are divided into 2 major categories: one is drugs with high concentration in the urine and relatively low solubility, including triamterene, drugs for HIV infection (such as indinavir), magnesium silicate and sulfonamides, which are themselves components of stones. Another group of drugs that can induce stone formation include acetazolamide, Vit D/Vit C and corticosteroids, which are metabolized in the process of leading to the formation of stones of other components. Second, what are the common clinical manifestations? Usually, kidney stones in children are asymptomatic and may manifest as microscopic hematuria, with some presenting as carnivorous hematuria. If the stone obstructs the renal pelvis or ureter, obvious clinical manifestations appear. Older children show severe colic in the lower back or abdomen, and infants may have paroxysmal crying, vomiting and pallor, which may be misdiagnosed as appendicitis. It is easy to develop secondary urinary tract infection, hydronephrosis, urinary tract obstruction, and even renal insufficiency. Hematuria is often the first symptom of kidney stones in children, which can disappear on its own and recur. About 2.16% of children with problematic formula present with hematuria, which is much higher than the screening rate for hematuria in normal children (0.5% to 1%). In some children, stones may be excreted in the urine or there may be temporary anuria, suggesting the formation of an obstruction. The main clinical symptoms of renal calculi in infants and children are: (a) unexplained crying, especially during urination, which may be accompanied by vomiting; (b) visual or microscopic hematuria; (c) acute obstructive renal failure, which is characterized by oliguria or anuria; (d) stones may be excreted in the urine, such as painful urination and difficult urination in boys with stones obstructing the urethra; (e) hypertension, edema, and percussion pain in the kidney area.