In recumbent elderly patients, creatinine clearance (eCCr) estimated by the Cockcroft-Gault (CG) equation may not necessarily reflect renal function. We aimed to develop a novel formula to revise the CG equation using anthropometric measurements in bedridden elderly patients and evaluate its clinical utility. The subjects included 77 bedridden Japanese patients aged ≦ 65, hospitalized at Naruto Yamakami Hospital. The actual CCr (mCCr) value was measured using the 24-hour urine collection method. Anthropometric data, such as skeletal muscle mass, body fat mass (BFM), and triceps skinfold thickness (TSF), were collected. We established a novel formula to estimate CCr(BFM) or CCr(TSF) by correcting the eCCr(Enz+0.2) value with BFM or TSF. The stage of classification of renal dysfunctions in patients with eGFR(BFM) or eGFR(TSF) was equivalent to the GFR(control) based on the mCCr. Notably, the novel equation for eCCr based on TSF (eCCr(TSF)), dubbed the "Naruto" formula, can be useful to evaluate renal function in bedridden elderly patients without expensive equipment or additional costs. In this study, mCCr was considered to be the true renal function of the patient, but whether and to what extent mCCr correlates with inulin clearance is unknown. J. Med. Invest. 65:195-202, August, 2018.
Keywords: bedridden elderly patients; creatinine clearance; estimation of renal function; triceps skinfold thickness; “Naruto" formula.