Clinical Signs, Causes, and Risk Factors of Pediatric Kidney Stone Disease: A Hospital-Based Case-Control Study

Kidney stones are one of the most common chronic kidney diseases and urinary tract in children and long-term detrimental effects on the kidneys of the child is one of the major causes of children mortality (1). The prevalence of kidney stones in different parts of the world is reported 1% - 15% (2, 3). About 7% of urinary stones are observed in the category under 17 years old (2). It seems that kidney stone is a common disease among adults, but more children are diagnosed with this condition recently. Increased diagnosis of pediatric kidney stone is due to rapid development in radiological imaging and greater awareness among physicians (4, 5). Important causes of this medical problem in children are poor nutrition, sedentary life habits, fluid intake, and the use of inappropriate medication. In addition, several risk factors such as age, gender, genetics, geographical factors, and weather also contribute to its development. For example, in Iran the incidence of kidney stones is 1.7% - 4.1% in children aged 4 to 9 years; whereas, in America it is one in 100,000 children (6-8). Since the early diagnosis of the disease reduces the risk of recurrent kidney stones, awareness of its symptoms and risk factors are quite necessary (9, 10). Iran is on the kidney stone belt (9). That is why it is essential to conduct researches on the prevalence and etiology of this disease in Iran. Therefore, the current study aims at identifying epidemiological characteristics and risk factors of nephrolithiasis among children under 18 years old attending at nephrology clinic of Amir Kabir hospital of Arak in 2014.

The current study investigated the causes and risk factors of pediatric nephrolithiasis using a case-control study with 2 equal groups of 83 children. Table 1 describes socio-demographic and individual characteristics of the participants. Investigating clinical problems revealed that the most common symptoms of pediatric nephrolithiasis included fever (81.1%), urine discoloration (8.4%), pain (6%), and dysuria (3.6%). Nearly one-third (39.4%) of the participants had a combination of symptoms simultaneously. Urinary tract infection (42.2%) was the most common cause to seek medical care.

The univariate logistic regression was run to identify the associations between several variables and nephrolithiasis. The odd ratio and 95% confidence interval (CI) are presented in Table 2. There were significant associations (P < 0.05) between nephrolithiasis and father’s occupation, growth retardation, growth cessation, growth failure, normal growth, weight-for-height percentile, BMI, gestational age, and type of nutrition during infancy. The likelihood of having kidney stone was higher among children with self-employed fathers. In addition, children with higher BMI, weight-to-height percentile were less likely to have kidney stone. However, it was found that odds of having stone were higher among children born pre term compared to the ones born full term.

Significant variables of univariate logistic regression model were included in the multiple logistic regression. Results of the multiple logistic regression indicated that father’s occupation, type of nutrition during infancy, weight-to-height percentile, BMI, and gestational age were significant predictors of nephrolithiasis (Table 2).

Pediatric nephrolithiasis is a painful and costly disease that may have long term effects on the function of kidney (11-15). The results of the current study showed that the most common symptoms of kidney stone were fever followed by urine discoloration, pain, and dysuria, respectively. However, one-third of the subjects experienced a combination of several symptoms simultaneously. While some specialists believe that signs and symptoms of stones are non-specific and ambiguous, others claim that the most common symptom to seek medical care is hematuria (5). Findings of the present study were consistent with those of some previous researches that indicated the most prevalent symptom of kidney stone was hematuria followed by dysuria, pain, fever, and agitation (16-24). And in the current study, the most common cause was urinary tract infections, consistent with some other studies including the study by Mohkem et al. who helped the children admitted to hospital during 5 years (1383 - 1387) where the most common clinical presentation was hematuria (6).

The study subjects were mainly younger than 5 years old, which might be due to selecting patients from a clinic. Children younger than 5 years old usually express non-specific symptoms that require visiting a pediatrician at a clinic. However, there is a tendency to visit an urologist among older children with more specific symptoms such as hematuria and urinary tract infection. Results of the present study revealed no significant difference in age range of cases and controls. This finding was consistent with those of several studies (11, 19, 20). This is while AlPlay et al. suggested the mean age of diagnosis 5.59 years (21).

Another finding of the current study was the significant associations obtained from simple logistic regression models between nephrolithiasis and father’s occupation, growth retardation, growth cessation, growth failure, normal growth, weight-to-height percentile, BMI, gestational age, and the type of nutrition during infancy. The likelihood of having kidney stone was higher among children with self-employed fathers. In addition, children with higher BMI, weight and height percentile were less likely to have kidney stone. However, it was found that the odds of having stone were higher among children born full-term compared to the ones born pre-term. Family history of nephrolithiasis was reported as an important risk factor to develop stone among children (16, 22, 23). Recognizing risk factors of kidney stone among children may lead to early diagnosis and better prognosis of the condition.