The glomerular filtration rate (GFR) has become the standard means of evaluating renal function and has traditionally been estimated from creatinine clearance or the serum creatinine concentration. Unfortunately, both of these estimations are frequently inaccurate, particularly in children. For creatinine clearance measurements, a carefully timed urine sample is required, the results of which are often inaccurate. Serum creatinine concentration is affected by factors other than GFR, such as the production of creatinine, which is primarily related to muscle mass. Because of the variability among children in size and body habitus, this measure can also result in erroneous GFR readings.

Over the years, several calculations have been developed for estimating GFR, all of which have their shortcomings when used on various populations and under various circumstances (Table 141.1,). For example, the Cockcroft and Gault formula, which has been the most commonly used formula, systematically overestimates GFR values in obese and edematous people. A better formula was developed by Levey et al. that reduces variability in measurement among different population types. Special studies have been conducted to analyze the effectiveness of using traditional GFR estimation strategies on pediatric patients. In a 2003 study, Hogg et al. identified several metrics for more accurately measuring creatinine clearance in children and adolescents given conditions such as diabetes. Two formulae in particular were found to be much more practical for pediatric use (Table 141.2,). If renal insufficiency exists in a pediatric patient, it is essential to remember that renal impairment may require drug dosage alterations or therapeutic drug monitoring. Detailed alterations specific to each drug can be found in various pharmacological textbooks or databases. Therapeutic drug monitoring can also be used to measure the changes in drug levels administered to patients suffering from renal insufficiency or failure. For example, Livernese et al. studied the use of antibacterial agents in renal failure and provided good information about drug management in patients with renal failure.