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Schwartz GFR Calculator (Original & Bedside)

Standard pediatric GFR estimator. Features auto-selection of K-constant for Preterm, Term, Children, and Adolescent Males.

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Current Constant k = 0.55
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About

The Schwartz formula is the ubiquitous method for estimating renal function in children and adolescents (ages 0-18). Accurate GFR estimation in this group is challenging due to rapid changes in muscle mass and body surface area during growth.

This tool combines both the Original Schwartz (1976) logic, which utilizes specific "k" constants for different developmental stages (including preterm infants and adolescent males), and the updated Bedside Schwartz (2009), which uses a unified constant for standard measurements. The interface minimizes error by auto-selecting the appropriate constant based on the user's selected age and gender category.

pediatrics gfr schwartz formula child kidney function nephrology

Formulas

The core mathematical structure follows a linear relationship between height and creatinine:

eGFR = k × Length (cm)Scr (mg/dL)

Where k is the proportionality constant derived from muscle mass per unit of body height.

Reference Data

Patient CategoryK-ConstantCondition
Preterm Infant0.33< 1 year, low birth weight
Full-Term Infant0.45< 1 year
Child / Adolescent (F)0.551 - 18 years
Adolescent (M)0.7013 - 18 years

Frequently Asked Questions

The Original Schwartz (1976) uses multiple K-values (0.33-0.70). The "Bedside" Schwartz (2009) was updated for methods using IDMS-traceable creatinine and typically simplifies the constant to 0.413 for all children, though the original constants remain useful for specific developmental nuances.
Generally, once growth plates close and muscle mass stabilizes (around 18-19), adult formulas like CKD-EPI become more accurate.