estimated gfr (eGFR) - Neonatal Disorders

What is eGFR?

The estimated glomerular filtration rate (eGFR) is a crucial measure used to evaluate kidney function in both adults and children. It estimates how much blood passes through the glomeruli (tiny filters in the kidneys) each minute. In pediatrics, accurately assessing kidney function is essential for diagnosing and managing various renal conditions.

Why is eGFR Important in Pediatrics?

Children are not just small adults; their kidneys are still developing. Monitoring eGFR in pediatrics helps in early detection of chronic kidney disease (CKD), guiding treatment plans, and adjusting medication dosages. Early interventions can slow disease progression and improve overall outcomes.

How is eGFR Calculated in Children?

In pediatrics, eGFR is commonly calculated using the Schwartz formula, which takes into account the child's height and serum creatinine levels. The formula is:

eGFR = (k * height) / serum creatinine

Here, "k" is a constant that varies with age and sex, and height is measured in centimeters. Serum creatinine is measured in milligrams per deciliter (mg/dL). This formula provides an estimate that adjusts for the child’s growth and development.

Factors Affecting eGFR in Pediatrics

Several factors can influence eGFR in children, including:

Age and growth: As children grow, their muscle mass increases, affecting serum creatinine levels.
Gender: Boys and girls may have different creatinine levels due to differences in muscle mass.
Nutrition: Malnutrition or obesity can impact muscle mass and serum creatinine levels.
Medications: Some drugs can affect kidney function or interfere with creatinine measurement.
Underlying health conditions: Diseases like diabetes, hypertension, or congenital kidney anomalies can affect eGFR.

What are Normal eGFR Values for Children?

Normal eGFR values in children vary with age. Generally, infants have lower eGFR values that increase as they grow. For example:

Newborns: 20-30 mL/min/1.73m2
Infants (2-12 months): 50-90 mL/min/1.73m2
Children and adolescents: 90-120 mL/min/1.73m2

Values below these ranges may indicate impaired kidney function and warrant further investigation.

How to Interpret eGFR in Pediatric Patients?

Interpreting eGFR in pediatrics requires considering the child’s overall clinical picture, including symptoms, urinalysis, and imaging studies. A low eGFR might indicate acute kidney injury (AKI) or chronic kidney disease (CKD), and the cause needs to be identified.
Staging of CKD in children is similar to adults and is based on eGFR values:

Stage 1: eGFR ≥ 90 mL/min/1.73m2 with kidney damage
Stage 2: eGFR 60-89 mL/min/1.73m2
Stage 3: eGFR 30-59 mL/min/1.73m2
Stage 4: eGFR 15-29 mL/min/1.73m2
Stage 5: eGFR

Challenges in Measuring eGFR in Pediatrics

One of the challenges in measuring eGFR in children is obtaining an accurate serum creatinine level. Factors such as hydration status and laboratory variability can affect results. Additionally, different formulas may be needed for infants, toddlers, and adolescents due to their varying growth rates.

Management of Abnormal eGFR in Children

If a child has an abnormal eGFR, further tests are usually required to determine the underlying cause. These may include:

Blood tests for electrolytes, blood urea nitrogen (BUN), and other markers of kidney function.
Imaging studies like ultrasound or MRI to visualize the kidneys.
Urinalysis to check for protein, blood, or other abnormalities.

Treatment depends on the underlying cause and may involve dietary changes, medications, or in severe cases, dialysis or kidney transplantation.

Conclusion

Monitoring eGFR in pediatric patients is essential for early detection and management of kidney diseases. Given the unique physiological characteristics of children, specialized approaches such as the Schwartz formula are used to provide an accurate estimate of kidney function. Understanding and interpreting eGFR in the context of a child's overall health is vital for effective treatment and improved outcomes.