Although urinary system stone disease is relatively less common in children than adults, its frequency has increased in recent years. While a sedentary lifestyle, changing eating habits and inappropriate vitamin use play an important role in this increase, the widespread use of ultrasonography and increased awareness about stones have made diagnosis easier and more frequent (9).
The frequency, etiology, type, content, and location of urinary system stones are associated with geography. The incidence varies worldwide; It is most frequently seen in endemic regions such as Türkiye and Thailand (10). It has been reported that there is a genetic predisposition to the development of urinary system stones and that half of the children with stones have a family history of stones (11). In this study, a family history of stones was found to have a frequency of 61.4%, consistent with the literature.
Urinary system stones are more common in males in adulthood. Male dominance has also been reported in some child studies (12). However, consistent with our study, it is accepted that there is no gender difference in childhood (13,14). In the present study, 51.6% (n=63) of 122 patients were male, and 48.4% (n=59) were female, and there was no statistical gender difference.
Complaints and findings of the patients at admission vary depending on the age of the patient, the location and size of the stone and whether it causes obstruction, the presence of accompanying urinary tract infection (UTI), and the presence of underlying structural or functional genitourinary anomalies (12-15). The most common symptom in children with urinary system stones is flank or abdominal pain. Infants and young children often cannot express the existence, location, and severity of pain and usually present with nonspecific complaints such as restlessness. Apart from pain or restlessness, these patients may experience hematuria, dysuria, urgency symptoms suggestive of UTI, and nausea/vomiting (16). Fifteen to 20% of children with urinary tract stones are asymptomatic, mainly young children whose stones are detected when abdominal imaging is performed for other purposes (17). In our study, 9% of the patients were children whose stones were detected incidentally while examined for another reason. The most common complaints in our remaining patients were abdominal pain, side pain, or restlessness; clinical findings suggestive of urinary tract infection (or history of UTI); nausea/vomiting; and hematuria. The presenting symptoms of our patients were similar to those in previously reported pediatric studies (13,14,18,19).
Twenty to 25% of children with urinary tract stones have a urinary tract infection or a history of infection. Infection may be the primary cause of a stone or may occur along with an underlying urinary metabolic or structural abnormality. Functional or anatomical obstructions of the urinary tract predispose to stasis and infection, possibly encouraging stone formation. Advances in early detection and repair of obstructive uropathies have reduced the incidence of stones due to infections. In this study, one-fifth of the patients had a history of active or previous urinary tract infections at admission, but no one had struvite stones.
Similar to previous studies, our study observed that most urinary system stones (83.6%) were in the upper urinary system (13,14,18,19). None of our patients had bladder stones. The decrease in the incidence of bladder stones is attributed to changes in eating habits.
In addition to detecting urinary system stones, ultrasonography provides the advantage of anatomical evaluation. In case series of children with urinary tract stones, structural abnormalities (such as hydronephrosis, double collecting system, posterior urethral valve, and bladder anomalies) have been reported in 10 to 25 percent of patients (14,15). Congenital and structural abnormalities accompanied by urinary stasis are associated with kidney stones. Urine stasis paves the way for crystal and stone formation. This study detected structural urinary system anomalies in 14 children (11.4%). Studies from our country reported 3 to 20% of urinary system anomalies (13,14,18).
Most urinary tract stones in children are associated with one or more metabolic disorders. It is important to reveal the underlying metabolic causes in order to apply an effective treatment method. Metabolic studies consist of blood and urine analyses. Hypercalcemia, hyperuric acidemia, high vitamin D, hyperparathyroidism, metabolic acidosis, or alkalosis can be informative in revealing some diseases that may cause urinary system stones. These results guide the diagnosis, diet, and drug treatments of primary diseases (such as renal tubular diseases).
Metabolic etiology in adults is not as common as in children. For this reason, while metabolic evaluation is recommended only for those with recurrent stones in adults, it is recommended when the first stone is detected in children (7,8). The basis of metabolic assessment is measuring the amounts of solutes in the urine that predispose to stone formation. This is calculated by measuring their amounts in 24-hour urine or by the ratio of each solute to creatinine in spot urine and comparing them with normal age (13,14,18,19). In this study, metabolic evaluations were made by spot urine solute/creatinine measurements.
Two mechanisms explain why metabolic factors cause stone formation. First, increased renal excretion of solutes such as calcium, oxalate, uric acid, and cystine or increased urinary concentrations due to low urine volume. This leads to supersaturation and precipitation of the solute, resulting in the formation of crystals that can aggregate into a stone. Second, natural inhibitors of urinary stone formation are scarce, such as citrate, magnesium, and pyrophosphate. Low levels of these inhibitors, especially hypocitraturia, are associated with kidney stones in adults and children. In two case series of children with kidney stones, approximately 90 percent of the patients had at least one metabolic risk factor (7,20). In some studies from our country, Alpay et al. (18) in 87% of patients, Melek et al. (13) in 69.7%, and Taşdemir et al. (14) in 34.8% detected a metabolic cause. Our study found one or more metabolic disorders in 58.2% of the patients.
The most common metabolic abnormality associated with pediatric stone disease is hypercalciuria (21). In most of the studies conducted in our country, hypercalciuria was found to be the most common cause, while in some studies, hypocitraturia was reported more frequently (13,14,18,22). In our study, a single metabolic disorder was detected in 53.3% of the patients, and nearly half of them (20.5%) were hypercalciuria. The rise in excretion of calcium in the urine can be attributed to three mechanisms: increased intestinal absorption (absorptive hypercalciuria), renal tubular calcium reabsorption defect (renal hypercalciuria), and increased bone resorption (resorptive hypercalciuria) (23). Inadequate fluid intake, immobilization, medications such as diuretics and glucocorticoids, excessive vitamin D, and high-salt diets are environmental factors that can cause hypercalciuria.
Other metabolic abnormalities detected in our study were hypocitraturia, hyperoxaluria, hyperuricosuria, cystinuria, and hypomagnesuria, respectively. Citrate is an inhibitor of calcium oxalate and calcium phosphate crystallization. Hypocitraturia is more common in adult patients with idiopathic kidney stones than in children. Although hypocitraturia is mostly idiopathic, a diet rich in animal proteins and low in potassium and plant foods contributes to a decrease in citrate excretion (24).
In our study, hypocitraturia was the second most common cause of stones and was present in 17.2% of the patients. This rate was similar to that of some child studies in our country (19,25). Furthermore, hypocitraturia (34.1%) was the predominant metabolic abnormality observed in our patients whose stones reduced in size or disappeared.
Oxalate, the end product of glyoxylate and ascorbic acid metabolism, is excreted through the kidneys. In our study, hyperoxaluria was the third most frequently detected metabolic disorder. None of our patients had primary hyperoxaluria, which is a genetic-metabolic disease. Idiopathic hyperuricosuria is thought to result from a defect in renal tubular uric acid excretion, and hyperuricosuria is detected in 2 to 8 percent of children with urinary stones. Although Elmaci et al. (26) and Kara et al. (19) have reported that hyperuricosuria is the most common metabolic disorder in children in our country, the frequency of hyperuricosuria in our study was found to be in line with the frequency reported in the literature. More than one metabolic disorder may occur together in some children with urinary system stones (14,18). In 4.9% of our patients, we have identified more than one metabolic disorder.
As a result, in this retrospective study conducted in children with urinary system stones, there was no gender difference, family history was common, the most common presenting symptom was abdominal/flank pain or restlessness, stones were generally located in the upper urinary system, microlithiasis was found at a considerable rate, anatomical problems could be detected, the most common presenting symptom was abdominal/flank pain or restlessness. It has been determined that the important predisposing factor is a metabolic disorder and that most of the stones shrink and disappear completely with medical treatment.
DISCUSSION
Although urinary system stone disease is relatively less common in children than adults, its frequency has increased in recent years. While a sedentary lifestyle, changing eating habits and inappropriate vitamin use play an important role in this increase, the widespread use of ultrasonography and increased awareness about stones have made diagnosis easier and more frequent (9).
The frequency, etiology, type, content, and location of urinary system stones are associated with geography. The incidence varies worldwide; It is most frequently seen in endemic regions such as Türkiye and Thailand (10). It has been reported that there is a genetic predisposition to the development of urinary system stones and that half of the children with stones have a family history of stones (11). In this study, a family history of stones was found to have a frequency of 61.4%, consistent with the literature.
Urinary system stones are more common in males in adulthood. Male dominance has also been reported in some child studies (12). However, consistent with our study, it is accepted that there is no gender difference in childhood (13,14). In the present study, 51.6% (n=63) of 122 patients were male, and 48.4% (n=59) were female, and there was no statistical gender difference.
Complaints and findings of the patients at admission vary depending on the age of the patient, the location and size of the stone and whether it causes obstruction, the presence of accompanying urinary tract infection (UTI), and the presence of underlying structural or functional genitourinary anomalies (12-15). The most common symptom in children with urinary system stones is flank or abdominal pain. Infants and young children often cannot express the existence, location, and severity of pain and usually present with nonspecific complaints such as restlessness. Apart from pain or restlessness, these patients may experience hematuria, dysuria, urgency symptoms suggestive of UTI, and nausea/vomiting (16). Fifteen to 20% of children with urinary tract stones are asymptomatic, mainly young children whose stones are detected when abdominal imaging is performed for other purposes (17). In our study, 9% of the patients were children whose stones were detected incidentally while examined for another reason. The most common complaints in our remaining patients were abdominal pain, side pain, or restlessness; clinical findings suggestive of urinary tract infection (or history of UTI); nausea/vomiting; and hematuria. The presenting symptoms of our patients were similar to those in previously reported pediatric studies (13,14,18,19).
Twenty to 25% of children with urinary tract stones have a urinary tract infection or a history of infection. Infection may be the primary cause of a stone or may occur along with an underlying urinary metabolic or structural abnormality. Functional or anatomical obstructions of the urinary tract predispose to stasis and infection, possibly encouraging stone formation. Advances in early detection and repair of obstructive uropathies have reduced the incidence of stones due to infections. In this study, one-fifth of the patients had a history of active or previous urinary tract infections at admission, but no one had struvite stones.
Similar to previous studies, our study observed that most urinary system stones (83.6%) were in the upper urinary system (13,14,18,19). None of our patients had bladder stones. The decrease in the incidence of bladder stones is attributed to changes in eating habits.
In addition to detecting urinary system stones, ultrasonography provides the advantage of anatomical evaluation. In case series of children with urinary tract stones, structural abnormalities (such as hydronephrosis, double collecting system, posterior urethral valve, and bladder anomalies) have been reported in 10 to 25 percent of patients (14,15). Congenital and structural abnormalities accompanied by urinary stasis are associated with kidney stones. Urine stasis paves the way for crystal and stone formation. This study detected structural urinary system anomalies in 14 children (11.4%). Studies from our country reported 3 to 20% of urinary system anomalies (13,14,18).
Most urinary tract stones in children are associated with one or more metabolic disorders. It is important to reveal the underlying metabolic causes in order to apply an effective treatment method. Metabolic studies consist of blood and urine analyses. Hypercalcemia, hyperuric acidemia, high vitamin D, hyperparathyroidism, metabolic acidosis, or alkalosis can be informative in revealing some diseases that may cause urinary system stones. These results guide the diagnosis, diet, and drug treatments of primary diseases (such as renal tubular diseases).
Metabolic etiology in adults is not as common as in children. For this reason, while metabolic evaluation is recommended only for those with recurrent stones in adults, it is recommended when the first stone is detected in children (7,8). The basis of metabolic assessment is measuring the amounts of solutes in the urine that predispose to stone formation. This is calculated by measuring their amounts in 24-hour urine or by the ratio of each solute to creatinine in spot urine and comparing them with normal age (13,14,18,19). In this study, metabolic evaluations were made by spot urine solute/creatinine measurements.
Two mechanisms explain why metabolic factors cause stone formation. First, increased renal excretion of solutes such as calcium, oxalate, uric acid, and cystine or increased urinary concentrations due to low urine volume. This leads to supersaturation and precipitation of the solute, resulting in the formation of crystals that can aggregate into a stone. Second, natural inhibitors of urinary stone formation are scarce, such as citrate, magnesium, and pyrophosphate. Low levels of these inhibitors, especially hypocitraturia, are associated with kidney stones in adults and children. In two case series of children with kidney stones, approximately 90 percent of the patients had at least one metabolic risk factor (7,20). In some studies from our country, Alpay et al. (18) in 87% of patients, Melek et al. (13) in 69.7%, and Taşdemir et al. (14) in 34.8% detected a metabolic cause. Our study found one or more metabolic disorders in 58.2% of the patients.
The most common metabolic abnormality associated with pediatric stone disease is hypercalciuria (21). In most of the studies conducted in our country, hypercalciuria was found to be the most common cause, while in some studies, hypocitraturia was reported more frequently (13,14,18,22). In our study, a single metabolic disorder was detected in 53.3% of the patients, and nearly half of them (20.5%) were hypercalciuria. The rise in excretion of calcium in the urine can be attributed to three mechanisms: increased intestinal absorption (absorptive hypercalciuria), renal tubular calcium reabsorption defect (renal hypercalciuria), and increased bone resorption (resorptive hypercalciuria) (23). Inadequate fluid intake, immobilization, medications such as diuretics and glucocorticoids, excessive vitamin D, and high-salt diets are environmental factors that can cause hypercalciuria.
Other metabolic abnormalities detected in our study were hypocitraturia, hyperoxaluria, hyperuricosuria, cystinuria, and hypomagnesuria, respectively. Citrate is an inhibitor of calcium oxalate and calcium phosphate crystallization. Hypocitraturia is more common in adult patients with idiopathic kidney stones than in children. Although hypocitraturia is mostly idiopathic, a diet rich in animal proteins and low in potassium and plant foods contributes to a decrease in citrate excretion (24).
In our study, hypocitraturia was the second most common cause of stones and was present in 17.2% of the patients. This rate was similar to that of some child studies in our country (19,25). Furthermore, hypocitraturia (34.1%) was the predominant metabolic abnormality observed in our patients whose stones reduced in size or disappeared.
Oxalate, the end product of glyoxylate and ascorbic acid metabolism, is excreted through the kidneys. In our study, hyperoxaluria was the third most frequently detected metabolic disorder. None of our patients had primary hyperoxaluria, which is a genetic-metabolic disease. Idiopathic hyperuricosuria is thought to result from a defect in renal tubular uric acid excretion, and hyperuricosuria is detected in 2 to 8 percent of children with urinary stones. Although Elmaci et al. (26) and Kara et al. (19) have reported that hyperuricosuria is the most common metabolic disorder in children in our country, the frequency of hyperuricosuria in our study was found to be in line with the frequency reported in the literature. More than one metabolic disorder may occur together in some children with urinary system stones (14,18). In 4.9% of our patients, we have identified more than one metabolic disorder.
As a result, in this retrospective study conducted in children with urinary system stones, there was no gender difference, family history was common, the most common presenting symptom was abdominal/flank pain or restlessness, stones were generally located in the upper urinary system, microlithiasis was found at a considerable rate, anatomical problems could be detected, the most common presenting symptom was abdominal/flank pain or restlessness. It has been determined that the important predisposing factor is a metabolic disorder and that most of the stones shrink and disappear completely with medical treatment.