title: [Impaired renal function: be aware of exogenous factors].
abstract: BACKGROUND
  Renal function is currently estimated using the Modification of Diet in Renal Disease (MDRD) formula, which is partly based on the serum creatinine level. Patients with impaired renal function are referred to nephrologists in accordance with the Dutch national transmural agreement for 'Chronic renal impairment'.
  
  
  METHODS
  A 54-year-old woman without significant history was referred to analyse a coincidentally found decline in the estimated glomerular filtration rate (eGFR). The patient had no complaints and used no medication except creatine supplements. Additional diagnostic testing showed no abnormalities. After cessation of creatine supplementation, the calculated renal function normalized.
  
  
  CONCLUSIONS
  Serum creatinine is a reflection of muscle mass. The use of creatine-containing dietary supplements, such as creatine ethyl ester, can influence serum creatinine levels and therefore the eGFR as calculated with the MDRD formula. The use of supplements deserves attention when taking the history.
authors.affiliation: Albert Schweitzer ziekenhuis, afd. Interne Geneeskunde, Dordrecht, the Netherlands. w.vandermeijden@erasmusmc.nl
authors.forename: Wilbert A G
authors.initials: WA
authors.lastname: van der Meijden
authors.forename: Peter J H
authors.initials: PJ
authors.lastname: Smak Gregoor
mesh_terms: D003401:Creatine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D003404:Creatinine / Q000097:blood*; D004032:Diet; D019587:Dietary Supplements / Q000009:adverse effects*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D051437:Renal Insufficiency / Q000097:blood / Q000175:diagnosis / Q000209:etiology*
chemical_list: D003404:Creatinine; C542315:creatine ethyl ester; D003401:Creatine