Kids with asthma are four times more likely to have kidney stones.
Children with asthma are four times more likely than the general population to have kidney stones, and children with kidney stones are four times more likely to have asthma.
Those are the findings of a new Cleveland Clinic study based on data from 865 pediatric nephrolithiasis patients. The researchers compared data from those patients to statistics from more than a half-million children in the health system’s network.
The researchers noted that kidney stones have already been linked to metabolic and genetic abnormalities, including cystic fibrosis (CF). According to the authors, the increased instance of kidney stones in patients with CF and asthma may suggest a link between respiratory inflammation and how renal tubes handle electrolytes.
While the prevalence of nephrolithiasis among the network’s overall pediatric population was 0.08%, there was a 0.31% incidence rate of kidney stones among pediatric asthmatic patients. Similarly, the overall prevalence of asthma among Cleveland Clinic patients was 6.8%, but among patients with kidney stones, the rate of asthma was 26.7%.
“Although this is a correlation study, the data may suggest a mechanistic link between asthma and nephrolithiasis,” wrote Ganesh K. Kartha, MD, the corresponding author. “Further investigation is needed to elucidate the pathophysiologic origin of this relationship.”
According to Kartha, “The CFTR (cystic fibrosis transmembrane conductance regulator) mutation affects chloride ion channels causing known abnormalities in the respiratory epithelial secretions. It has been hypothesized that similar electrolyte handling in the renal epithelium may predispose CF patients to kidney stone formation”.
Other evidence also supports the idea of a relationship between respiratory inflammation and kidney stones, though the authors said no one has yet investigated the connection directly.
“Independently, nephrolithiasis has been associated with alterations in the glycosaminoglycan layer of the urothelium and asthma has been associated with changes in the glycosaminoglycan layer in the lung epithelium,” the authors wrote. “To our knowledge, there have been no investigations looking at inflammatory changes in the urothelium in asthma patients.”
The researchers considered a number of other possible causes for the link like body mass index (BMI), but the authors found no significant difference in the BMIs of kidney stone patients with asthma and those without.
A look at medication data suggested that patients with more severe asthma might be at a higher risk of kidney stones. However, the researchers also noted that most patients with mild and moderate asthma didn’t undergo pulmonary function tests, so it is difficult to draw broad conclusions about respiratory distress and kidney stones.
Also, since asthma-only patients rarely underwent imaging, it is impossible to know whether or not some of these patients had asymptomatic kidney stones.
The researchers pointed to one other possible cause — socioeconomic factors, which have been linked to higher instances of both asthma and kidney stones. However, the researchers did not have access to sufficient patient socioeconomic data to conclusively identify a link.
Still, the authors said the data they were able to piece together is enough to make a strong inference of a mechanistic link between asthma and kidney stones. They hope their study will be the first of many, eventually leading to a definitive explanation.
The study, titled “Co-occurrence of Asthma and Nephrolithiasis in Children,” was published Jan. 12 in the journal PLOS ONE.