Calculating glomerular filtration rate in a young man with a large muscle mass

The Medical Journal of Australia ISSN: 0025729X 21 August 2006 185 4 221-222 ©The Medical Journal of Australia 2006 www.mja.com.au Lessons from Practice rate (GFR) is therefore widely accepted as a b Numerous equations using the serum creatinine le developed to calculate estimated GFR (eGFR) (Box automated reporting of eGFR using the MDRD (m diet in renal disease) formula has been introduce tions exist, especially with extremes of body size illustrates the difficulties of calculating GFR for a p eru of ot S m creatinine level, the most commonly used measure kidney function in clinical practice, varies with factors her than kidney function. These include age, sex, muscle mass, and dietary protein intake. Glomerular filtration etter marker. vel have been 2). Recently, odification of d, but limita. Our patient erson with a large muscle mass, with different methods giving widely varying results. The recently published CARI (Caring for Australasians with renal impairment) guidelines recommend that serum creatinine level alone should not be used to measure kidney function, because of the multitude of factors other than renal function that can affect this marker. Serum creatinine is derived from the metabolism of creatine in muscle and the generation of creatinine tends to be proportional to muscle mass. In adults, the abbreviated (4-variable) MDRD, the 6-variable MDRD, and the Cockcroft–Gault equations generally provide reliable eGFRs. The Cockcroft–Gault formula is probably the most widely recognised formula for conversion of serum creatinine level, although with reductions below 60 mL/min it becomes increasingly inaccurate compared with the MDRD formula. Recently, the abbreviated MDRD formula has been used in the automated laboratory reporting of eGFR in Australia, given extensive validation with no correction needed for body surface area. It is important to note that the different units for GFR measurements Clinical record