RENO, NEV. — Increased body mass index is correlated with worsening proteinuria in children, Dr. Carolyn Abitbol said at the annual meeting of the American College of Nutrition.
The findings, which are the result of a retrospective observational case-matched study of 60 children with proteinuria, confirm the hypothesis that obesity contributes to a decline in the glomerular filtration rate, an indicator of kidney function, said Dr. Abitbol of the Division of Pediatric Nephrology at the University of Miami.
Low-birth-weight infants may be more likely to develop obesity in childhood because of disproportionate height deficits in this population, making low birth weight an independent risk factor for the progression of chronic kidney disease in children, she said. These children also are born with fewer nephrons, the functioning units of the mature kidney.
The study included 40 obese children: 16 low-birth-weight children (less than 1,200 g) and 24 children of normal birth weight (over 2,500 g). Obesity was defined as a body mass index of greater than the 95th percentile for age and gender.
The study also included 20 nonobese children of normal birth weight as clinical controls. All children in the study had proteinuric kidney disease. The researchers excluded any patients who had acute glomerulonephritis, immune-mediated nephritis, or overt diabetes, as well as patients who had HIV nephropathy.
Dr. Abitbol and her colleagues performed kidney biopsies of nine children in the obese, low-birth-weight group and all had focal segmental glomerulosclerosis (FSGS).
Among children in the normal-birth-weight, obese group, 16 children were biopsied and 14 had FSGS. Additionally, one patient had focal mesangial proliferative glomerulonephropathy, which probably is an early form of FSGS, Dr. Abitbol said. One patient had a membranous nephropathy, which is unique and immune mediated; the diagnosis was made after the exclusion criteria had been applied, she said.
In the control group, all children were biopsied and 14 had FSGS, 4 had mesangial glomerulonephropathy, 1 had minimal change, and 1 was membranous.
The researchers also compared mean renal survival relative to birth weight and found that low-birth-weight patients had a loss of glomerular filtration rate significantly earlier than did those of normal birth weight, despite having a diagnosis at relatively the same age.
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