Family History and Risk of Kidney Stones
ABSTRACT & COMMENTARY
Synopsis: The relative risk for kidney stones was 2.5-fold higher in those with a positive family history compared to those with a negative family stone history.
Source: Curhan GC, et al. J Am Soc Nephrol 1997;8:1568-1573.
Apositive family history of kidney stones is associated with an increased risk for kidney stones. However, whether the reasons for this increased risk are genetic, environmental, or a combination, is not well studied. Genetic factors that predispose to stone formation include hypercalciuria, incomplete renal tubular acidosis, defective oxalate transport, and hyperuricemia. Environmental influences such as geographic area and dietary intake are thought to play a role in stone formation as well. To evaluate the influence of family history on kidney stone formation, Curhan and colleagues studied a cohort of 37,999 male participants in the Health Professionals Follow-up Study. The potential interaction between family history and dietary factors on risk for stone formation was also assessed using a semi-quantitative food-frequency mail questionnaire. Twenty-four hour urines for calcium, oxalate, and uric acid were also collected in men with and without kidney stones.
Based on prevalent data at baseline in 1986, family history of kidney stones was at least three times more common in men with a personal history of kidney stones than in those without a stone history (age-adjusted prevalence odds ratio, 3.16). Between 1986 and 1994, an eight-year follow-up, 795 incident cases of symptomatic kidney stones were documented. After adjustment examined for age, the relative risk for kidney stones was 2.5-fold higher in those with a positive family history compared to those with a negative family stone history. The relative risk (RR) was significantly greater in men younger than 60 years of age than in those aged 60 and older (RR = 1.74).
The association between nutrient intake and risk of incident stones was also examined. Family history did not significantly change or modify the inverse relationship between dietary intake of calcium and potassium and risk of incident kidney stones. Supplemental calcium intake was not associated with increased stone risk. In men with incident stones and a positive family history, 24-hour urinary calcium, citrate, and calcium oxalate supersaturation were higher but not significantly different than those with a negative family stone history.
COMMENT BY KAMALJIT SETHI, MD
In men, a family history of kidney stones increases the risk of stone formation. Others have reported similar data in women. Interestingly, only one-fourth of stone patients in this study had a positive family history. This suggests that in three-fourths and, thus, the majority of stone-forming men, environmental and dietary factors may be more important than family history in terms of the risk for kidney stones. It should be noted that the family history did not disturb the relationship between high dietary calcium intake and reduced risk of stone formation. The high urinary citrate levels in those with a positive family history was a surprising new observation. Other published data will have to be awaited to confirm this observation and its significance. Citrate is a known urinary inhibitor that reduces stone formation, and reduced citrate levels are a frequent finding in stone patients.
Probably the most important advice that should be given to patients with a family history of stones is to maintain a dietary calcium intake of at least 1 g/d and to drink enough water to maintain a urine volume of about 2 L/d.
Gemfibrozil treatment of post-CABG patients with isolated low HDL has been associated with marked reduction in subsequent clinical events despite lack of any demonstrated angiographic benefit.
What is the single most important dietary advice to be given to a man with a family history of kidney stones?
a. Reduce protein intake < 1 g/kg/d.
b. Reduce calcium intake < 1 g/d.
c. Maintain calcium intake ³ 1 g/d.
d. None of the above
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