Serum creatinine concentration is a commonly used marker of
renal function because of its simplicity, availability, and
cost. Unfortunately, it is an insensitive marker of renal
function, in that the glomerular filtration rate (GFR) must be
75% below normal for the creatinine concentration to be
elevated. Cathy E. Langston, DVM, DACVIM As an alternative,
measuring the GFR can be useful in numerous situations commonly
encountered in practice, such as - Evaluating patients with
polyuria without azotemia to definitively exclude or diagnose
kidney disease as the underlying cause - Monitoring renal
function in patients with early kidney disease (i.e. annual
testing) to evaluate the efficacy of therapy - Monitoring for
further kidney injury in patients with suspected nonazotemic
kidney disease that must receive nephrotoxic drugs (e.g.
chemotherapeutics, aminoglycoside antibiotics) - Evaluating
patients in which nephrectomy is being considered (i.e. renal
neoplasia). Not all methods of GFR measurement are practical