In a study published online by the Clinical Journal of the American Society of Nephrology, researchers looked at data from 3,604 patients with chronic kidney disease. They checked for an association between CKD outcomes (death and dialysis) and a pair of factors related to muscle mass. Muscle mass has been shown to be predictive of these outcomes in other disease states. For the first factor, creatinine excretion in urine, doctors did find an association. Lower levels of urinary creatinine excretion were “strongly” associated with increased mortality and progression to end-stage renal disease. Yet when researchers looked at an even better indicator of muscle mass — bioelectrical impedance analysis, which estimates body fat — there was no association with worsening CKD. “There was nothing there. This suggests it is not just about muscle mass,” said Dr. F. Perry Wilson, a Yale nephrologist and assistant professor at Yale School of Medicine. “This opens the door to more sophisticated interventions.” This was the first study to examine both factors at the same time. “This presents something of a paradigm shift in how we should think of urine creatinine,” Wilson said. “In essence, it’s telling us more than we thought it was.” Wilson said the findings indicate that poor muscle quality may be the better prognosticator for CKD outcomes. “There’s a physiological function here we haven’t fully characterized yet,” he said. Reference: “Urinary Creatinine Excretion, Bioelectrical Impedance Analysis, and Clinical Outcomes in Patients with CKD: The CRIC Study” by F. Perry Wilson, Dawei Xie, Amanda H. Anderson, Mary B. Leonard, Peter P. Reese, Patrice Delafontaine, Edward Horwitz, Radhakrishna Kallem, Sankar Navaneethan, Akinlolu Ojo, Anna C. Porter, James H. Sondheimer, H. Lee Sweeney, Raymond R. Townsend, Harold I. Feldman and the CRIC Study Investigators, 5 December 2014, Clinical Journal of the American Society of Nephrology.DOI: 10.2215/CJN.03790414
