Short people with chronic kidney disease may be able to pin their vertical challenges on their birth weight, a new study suggests.

The finding is surprising, researchers said, because birth weight isn't known to be a factor for growth rate or height in anyone except chronic kidney disease patients.

Kids with chronic kidney disease who are born with a low weight have a slower growth rate and will therefore grow up to be shorter than kids with the disease born at normal weight, said study researcher Dr. Larry Greenbaum, director of pediatric nephrology at the Emory University School of Medicine in Georgia.

The study also suggests children born with a low weight have an increased risk of developing kidney disease, Greenbaum told MyHealthNewsDaily, though this finding needs to be confirmed by further research.

"There are studies in adults showing that being born with low birth weight increases the risk of kidney disease, [but] this was a somewhat surprising observation," he said. "We were not expecting the increase in low birth weight in the patients in the study."

Greenbaum and his colleagues examined 426 children, ages one to 16, who have chronic kidney disease. The researchers collected information on the kids' births, including their birth weights, if they were born premature and if they were admitted to an intensive care unit (ICU) after birth.

The researchers found 17 percent of kids had a low birth weight, 12 percent were born premature and 40 percent spent time in an ICU. The kids with the low birth weight (defined as being in the lowest 10 percent among newborns) were shorter and had slower growth rates than kids who weren't born small, the study said.

They also found kids with chronic kidney disease for nearly all their lives had a lower birth weight than kids who outgrew the disease as they got older.

It's still not known why body size seems to be related to kidney disease, but Greenbaum said the reason might lie in the kidney's capacity to filter blood.

A normal kidney "has about 1 million filters, but children who are born small may have far fewer," he said, affecting the kidney's ability to function.

The kids may have been affected by something while in the womb that caused them to have low birth weight, kidney disease and poor growth, he said. Another possibility is that the "catch-up" growth that usually happens in low birth-weight children can't happen because chronic kidney disease affects their growth.

If confirmed, the findings of this study could mean kids with low birth weights should be screened and monitored for chronic kidney disease, Greenbaum said.

The study was published online Oct .28 in the Clinical Journal of the American Society of Nephrology.