Gout patients at 60% greater risk for stone disease

Men and women with gout are at 60% greater risk for nephrolithiasis than adults without gout, according to a Swedish study looking at not only the chronic kidney condition’s incidence but also potential risk factors for first-time nephrolithiasis in people with and without gout.

A U.S. expert told Urology Times that the study provides additional data supporting the relationship between nephrolithiasis and diabetes mellitus, as well as obesity.

For the study, which was published in Arthritis Research & Therapy (2017; 19:173), researchers from the University of Gothenburg in Sweden looked at data from 30,000 gout cases and 138,678 matched controls from Jan. 1, 2006 to Dec. 31, 2012. They analyzed comorbidities and medication use in first-time nephrolithiasis, as well as potential socioeconomic risk factors. 

“The incidence of [nephrolithiasis] was consistently higher in patients with gout in all age and sex groups, compared to [general population] controls, with the highest incidence in patients with gout ages 20–39 years and in [general population] controls ages 60–79 years,” wrote the authors, led by Anton Landgren of the University of Gothenburg, Sweden.

Also see: Care utilization for stones growing rapidly in older adults

Predictors of nephrolithiasis were similar in both groups, except treatment with losartan (Cozaar). The high blood pressure drug, which had not been shown to be associated with increased nephrolithiasis risk in clinical trials, increased nephrolithiasis risk by 49% in this study, but only among controls.

Use of loop diuretics was one of two potentially modifiable risk factors of nephrolithiasis, decreasing risk of the kidney condition by 30% to 34% in gout cases and controls. Ironically, increased loop diuretic use increased gout exacerbation risk.

Obesity was the other modifiable risk factor in both groups.

Other predictors of nephrolithiasis in gout were being male and having diabetes. Among controls, risk factors for nephrolithiasis included being male and having kidney disease.

Among other findings that would interest urologists treating these patients, the study did not find that any of the other commonly used cardiovascular disease and anti-hypertension medications increased nephrolithiasis risk in patients with gout. And low doses of allopurinol, used to treat gout or kidney stones, provided no protective effect, according to the study.

Next: Dr. Matlaga discusses findings

Commenting on the study, Brian R. Matlaga, MD, MPH, of Johns Hopkins Medical Institutions, Baltimore and a member of the Urology Times Editorial Council, said the relationship between nephrolithiasis and gout has been reported prior to this study. But the new research provides additional data supporting the relationship between nephrolithiasis and diabetes mellitus, as well as obesity.

That’s important, said Dr. Matlaga, who was not involved with the study.

“Weight loss is associated with a myriad of health benefits, and this study emphasizes that a reduced risk of nephrolithiasis is one of them,” Dr. Matlaga said.

Dr. Matlaga said the finding that loop diuretics were associated with a decreased risk of nephrolithiasis is puzzling.

“Given the pharmacology of these medications, one would expect nephrolithiasis to increase, as the medications will promote hypercalciuria. As the study was not designed to test this relationship, it is difficult to assign a more meaningful conclusion to this finding,” he said.

Read: Vibration therapy promising for treating stone fragments

The study’s observational design also makes it difficult to draw a firm conclusion about the association between losartan and nephrolithiasis, according to Dr. Matlaga.

Dr. Matlaga said he’s cautious about the findings that none of the other commonly used drugs for cardiovascular disease and hypertension increased nephrolithiasis risk in those with gout and there was no protective effect from allopurinol, given in low doses.

“The study was observational, and not a priori designed to test these relationships,” he said.

But the findings that male gender, diabetes mellitus, and obesity were shown to increase risk of the condition are consistent with the current understanding of lithogenic risk factors, he said.

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