News tips from the 2006 annual meeting of the American Society of Nephrology, Nov. 14 to 19, San Diego.

SEVERITY OF HIGH BLOOD PRESSURE DOES NOT PREDICT EFFECT ON HEART IN CHILDREN

For children, even mild untreated high blood pressure can lead to a potentially dangerous enlargement of the heart, according to results of a study by researchers at the Johns Hopkins Children’s Center and the Children’s Hospital at Montefiore in Bronx, New York.

“It’s apparently not true for children, at least, that the higher the blood pressure the worse the strain on the heart, and that surprised us,” says kidney specialist Tammy Brady, M.D., a fellow at the Johns Hopkins Children’s Center. “In this study, children with minimally high, very high and severely high blood pressure had evidence of heart enlargement.”

Persistently elevated blood pressure, or hypertension is a well-known risk factor for left-ventricular hypertrophy (LVH), a thickening or enlarging of the lower left chamber of the heart, and the conventional wisdom has been that the degree of hypertension predicted the degree of LVH. Pediatric guidelines say that any elevation in pressure measured in children on three consecutive office visits is by definition evidence of hypertension.

In the Hopkins study, researchers examined 141 children seen at three medical centers from 1997 to 2005. All of the subjects, between the ages of 3 and 21, had primary hypertension, or high blood pressure not resulting from another underlying condition. Of the 141, 41 percent had LVH.

“Not only were our findings a surprise, but they are of concern given the growing numbers of children with high blood pressure, most likely due to spiraling rates of overweight and obesity,” Brady says.

Brady recommends ultrasound imaging of the heart for all children with hypertension. Untreated LVH in adults can lead to heart failure and increase the risk of sudden cardiac death.

RACIAL DISPARTIES IN CHILDREN WITH END-STAGE KIDNEY DISEASE

Anemia, an important marker of ill health, is persistently worse in African-American children with end-stage kidney disease than in their white counterparts, according to results of a study by scientists at the Johns Hopkins Children’s Center.

In an analysis of 677 patient records from a national registry, the Hopkins team found 71 percent of the white males, but only 59 percent of black males, had healthy levels of hemoglobin, the iron-rich oxygen transporters in red blood cells. Seventy-four percent of white girls had healthy levels, compared to 51 percent of black girls.

“Racial disparities are well-established among adult patients with kidney disease, but our findings show the same worrisome picture for children,” says Meredith Atkinson, M.D., a third-year nephrology fellow at the Children’s Center. “The next step is to figure out what combination of factors, such as differences in biology or access to health care, are responsible for the disparities.”

Patients with uncontrolled anemia, a well-known complication of kidney disease, generally have worse outcomes and worse quality of life than patients whose anemia is under control.

SIMPLE URINE TESTS ACCURATELY MEASURE KIDNEY FUNCTION

A simple urine test used widely to screen for kidney problems also appears to be a handy gauge of kidney function and disease progression in children with chronic kidney disease, according to results of research at the Johns Hopkins Children’s Center and several other institutions.

Researchers studied 92 children with mild to moderate kidney disease and found that increases in the amount of protein in the urine (proteinuria) corresponded directly to loss of kidney function. The relationship between proteinuria and loss of kidney function is well-established in adults, but had not been studied in children, particularly in those born with kidney disease.

“These results are quite encouraging because this test is fast, cheap and simple and is a really handy tool to help us track disease progression in children with kidney disease,” says Susan Furth, M.D., Ph.D., of the Johns Hopkins Children’s Center.

The current standard for tracking kidney function is GFR (glomerular filtration rate), a test conducted by injecting a contrast agent into the bloodstream and measuring how fast the kidneys remove it. By using both GFR and the urine tests, Furth and colleagues showed that, as proteinuria increased, GFR proportionately decreased.

“Now that we know that the urine tests accurately parallel what’s going on with kidney function, we’ll take the next step, which is to learn just how good the test is,” Furth says. “The hope is that eventually, we will be able to say with precision that ‘X’ amount of protein in the urine corresponds to a risk of ‘Y’ amount of kidney function loss.”

The findings are part of a continuing, multi-center study on pediatric kidney disease. Other institutions participating in the NIH study include the University of New Mexico; Children’s Mercy Hospital in Kansas City, Mo.; Oregon Health Sciences University; Children’s Hospital at Montefiore, Bronx, NY, and the University of Rochester, NY.