From the Guidelines
The estimated glomerular filtration rate (eGFR) for a 7kg female child with a serum creatinine of 1.1 mg/dL is approximately 22.3 mL/min/1.73m², indicating moderate to severe kidney dysfunction. To calculate the eGFR, we use the revised Schwartz formula, which is the preferred method for estimating GFR in children, as recommended by 1. The formula is eGFR = (0.413 × height in cm) ÷ serum creatinine. Since the height of the child is not provided, we assume an average height of 70 cm for a 7kg child.
Calculation
- eGFR = (0.413 × 70 cm) ÷ 1.1 mg/dL
- eGFR ≈ 22.3 mL/min/1.73m² This calculation is based on the revised Schwartz equation, which is considered more accurate than the original Schwartz equation, as it uses an enzymatic assay of creatinine that is traceable to an isotope-dilution mass spectrometry reference 1.
Clinical Implications
A serum creatinine of 1.1 mg/dL is significantly elevated for a child of this size, as normal values for young children are usually around 0.3-0.5 mg/dL. This child requires immediate nephrology consultation as this level of kidney dysfunction could indicate acute kidney injury or chronic kidney disease. Additional workup including urinalysis, blood pressure measurement, electrolytes, and kidney ultrasound would be warranted to determine the cause and appropriate management, as suggested by 1.
Key Points
- The revised Schwartz formula is the preferred method for estimating GFR in children.
- A serum creatinine of 1.1 mg/dL is significantly elevated for a child of this size.
- The child requires immediate nephrology consultation and additional workup to determine the cause and appropriate management.
From the Research
Estimating Glomerular Filtration Rate (eGFR) in Children
To estimate the eGFR for a 7-kilogram female child with impaired renal function and a serum creatinine level of 1.1 mg/dL, we can consider the following formulas and studies:
- The Schwartz formula, which has been widely used but has limitations, especially for children with less renal impairment or hyperfiltration 2, 3, 4.
- A new quadratic formula derived from a study in 2013, which may offer better accuracy for children with moderate renal failure but not for those with less renal impairment or hyperfiltration 2.
- The pediatric form of the Full Age Spectrum (FAS) equation, which can be an alternative to the Schwartz equation, especially when height is not available 3.
- Other formulas, such as the Leger GFR and Leger model, which have been evaluated for their precision and diagnostic characteristics 5.
Calculation Considerations
When calculating eGFR, it's essential to consider the child's height, serum creatinine level, and other factors, such as cystatin C and blood urea nitrogen 6. The formula that best fits the given data is the bedside calculation of 0.413*(height/serum creatinine), which provides a good approximation to the estimated GFR formula 6. However, to apply this formula, we need to know the child's height, which is not provided.
Available Formulas and Limitations
Given the available information, we can consider the following formulas:
- The quadratic formula derived from the 2013 study: 0.68 × (Height (cm)/serum creatinine (mg/dl))-0.0008 × (height (cm)/serum creatinine (mg/dl))(2)+0.48 × age (years)-(21.53 in males or 25.68 in females) 2. However, this formula requires the child's height and age, which are not fully provided.
- The bedside calculation of 0.413*(height/serum creatinine) 6, which also requires the child's height.
Limitations and Uncertainties
Due to the lack of specific information about the child's height and age, it's challenging to provide an accurate estimate of the eGFR using the available formulas. The studies cited highlight the limitations and uncertainties of estimating GFR in children, especially when using formulas that rely on height and serum creatinine levels 2, 3, 5, 4, 6.