Kidney stones mete out lifelong burden to patients with type 3 primary hyperoxaluria

Patients with primary hyperoxaluria type 3 carry a lifelong burden caused by kidney stones, according to a study, noting the importance of urinary calcium oxalate supersaturation reduction to decrease event frequency as well as surgical intervention.

A group of researchers retrospectively analysed the clinical and laboratory data of 70 patients with primary hyperoxaluria type 3 who were enrolled in the Rare Kidney Stone Consortium Primary Hyperoxaluria Registry. They characterized stone events and examined associations with urine parameters and kidney function in this population.

Of the patients, 65 (93 percent) developed kidney stones. Forty-nine patients had available imaging, which showed a median number of four stones, with the largest one having a size of 7 mm at first imaging. Clinical stone events occurred in 62 patients (89 percent), and the median number of events per patient was three.

The first stone event usually occurred at 3 years of age, with a lifetime stone event rate of 0.19 event per year during follow-up of 10.7 years. A total of 326 clinical stone events were recorded, of which 139 (42.6 percent) required surgical intervention. Stone events continued until 60 years for most patients.

In an analysis of 55 kidney stones, pure calcium oxalate accounted for 69 percent, with mixed calcium oxalate and phosphate in 22 percent. After adjusting for age at first event, higher calcium oxalate supersaturation significantly correlated with increased lifetime stone event rate (incidence rate ratio, 1.23, 95 percent confidence interval, 1.16‒1.32; p<0.001).

“By the fourth decade, estimated glomerular filtration rate was lower in primary hyperoxaluria type 3 patients than the general population,” the researchers said.