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Kidney Stone Disease Linked To Familial Hypertension

There is a strong, independent association between familial hypertension and the phenotype characterised by high urinary excretion of uric acid combined with high calcium. The association is not present in those with hyperuricosuria or hypercalciuria alone.

Finding patients based on the phenotype might identify more homogeneous populations for genetic analysis of hypertension, say researchers at Semmelweis University, Budapest, Hungary and the University of Toronto, Canada.

They note that past studies had found a link between kidney stone disease and hypertension. As hypercalciuria often occurs with hyperuricosuria, and as high urinary excretion of calcium occurs in hypertensive patients, the researchers looked into whether hyperuricosuria plus hypercalciuria might better describe the familial association between kidney stone disease and hypertension.

The researchers recruited 486 patients aged 18-50 years with kidney stone disease. The patients collected a 24-hour urine sample for metabolic analysis and provided information on family history of hypertension.

Familial hypertension was compared between four groups of patients:
- 56 with raised urinary calcium and uric acid excretions ('combined' abnormality): prevalence of treated hypertension 16 percent;
- 67 with hyperuricosuria without concomitant hypercalciuria ('pure' hyperuricosuria): prevalence of treated hypertension 12 percent;
- 52 with hypercalciuria without concomitant hyperuricosuria ('pure' hypercalciuria): prevalence of treated hypertension 2 percent;
- 311 control kidney stone disease patients ('other' abnormality): prevalence of treated hypertension 10 percent.

Of those with 'combined' abnormality, 34 percent had a positive family history of hypertension, defined as two or more first-degree relatives with treated hypertension.

That was significantly higher than in patients with 'pure' hyperuricosuria (15 percent), 'pure' hypercalciuria (8 percent) or 'other' abnormality (10 percent).

The adjusted odds ratio for positive family history of hypertension in the 'combined' abnormality group compared to the control kidney stone disease patient group was 5.6 (2.39-13.30).

The prevalence of hypertension in siblings of patients with the 'combined' abnormality (13 percent ) was significantly higher than in siblings of patients with 'pure' hyperuricosuria (3 percent ), 'pure' hypercalciuria (1 percent) or siblings of control patients with 'other' abnormality (4 percent).

The adjusted odds ratio for hypertension in siblings of a patient with 'combined' abnormality compared to a control kidney stone disease patient was 3.4 (1.97-5.91).

Patients in the 'combined' abnormality group also had significantly elevated urinary sodium, phosphorus, citrate and potassium excretions.
Nephrology Dialysis Transplantation 2002;17:253-259. "High urinary excretion of uric acid combined with high excretion of calcium links kidney stone disease to familial hypertension"

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