Glomerular Filtration Rate (GFR) is a measurement that indicates how well your kidneys are functioning. Your kidneys contain tiny filters called glomeruli, which are responsible for removing waste products and excess water from your blood. The GFR test estimates how much blood passes through these filters each minute, providing insight into your kidney’s filtering capacity. This measurement is a gauge of overall kidney health.
What is Pediatric GFR?
Pediatric GFR assesses how efficiently a child’s kidneys filter waste from their blood. The kidneys play a significant role in a child’s overall growth and development, making their proper function important during childhood. Children’s kidneys are still maturing, and their GFR values naturally change as they grow, reaching adult levels between one and two years of age.
A healthy GFR indicates a child’s kidneys are effectively removing waste, supporting their development. Conversely, a reduced GFR can signal impaired kidney function, potentially leading to complications like electrolyte imbalances, fluid overload, and waste buildup. Early detection of changes in GFR in children allows for timely intervention, which can help prevent the progression to more severe kidney conditions.
How Pediatric GFR is Measured
Pediatric GFR is primarily assessed through blood tests that measure substances like serum creatinine and cystatin C. Creatinine is a waste product from muscle activity, and healthy kidneys remove it from the blood. Cystatin C is another protein produced by the body that is filtered by the kidneys.
These blood values are then used in specific mathematical formulas to estimate GFR, referred to as estimated GFR or eGFR. For children, commonly used formulas include the Schwartz formula and equations developed from the Chronic Kidney Disease in Children (CKiD) study. These formulas take into account factors such as a child’s age, sex, height, and weight to provide a more accurate estimation of kidney function.
Understanding Your Child’s GFR Results
Understanding your child’s GFR results involves recognizing what different values signify for their kidney health. A normal GFR range for children varies based on age, sex, and body size. For instance, a healthy newborn’s eGFR might be between 40 and 60 mL/min/1.73 m², which would be considered low for an adult, but is typical as their kidneys are still maturing. By early childhood, around ages 1 to 5, GFR typically reaches near-adult levels, ranging from 90 to 110 mL/min/1.73 m².
A GFR value below 60 mL/min/1.73 m² for three months or more in children aged two years and older can indicate chronic kidney disease. A GFR below 15 mL/min/1.73 m² is a sign of kidney failure, requiring immediate medical attention. A GFR that is higher than the typical range for a child’s age, known as hyperfiltration, can also be a sign of certain underlying conditions or early stages of kidney disease.
Common Causes of Abnormal Pediatric GFR
Abnormal pediatric GFR can stem from various underlying health issues. Congenital anomalies of the kidney and urinary tract (CAKUT) are the most frequent cause of chronic kidney disease in children. These birth defects can include kidneys that are missing, abnormally small (hypoplasia), or malformed (dysplasia), or blockages in the urinary tract that hinder urine flow.
Acute kidney injury (AKI) can also lead to an abnormal GFR, characterized by a sudden decrease in kidney function. Common causes of AKI in children include severe dehydration, significant blood loss, certain medications toxic to the kidneys, or infections that disrupt blood flow. Glomerular diseases, such as glomerulonephritis and nephrotic syndrome, also affect the tiny filters in the kidneys. Glomerulonephritis involves inflammation of these filters, often occurring after infections like strep throat, while nephrotic syndrome leads to significant protein leakage into the urine.