Skeletal muscle mass effects on estimated glomerular filtration rate decrement after donor nephrectomy

Abstract

Background: Although it is well known that skeletal muscle mass influences the level of serum creatinine, the effect of skeletal muscle mass on decreased renal function after nephrectomy is not known. In this study we aimed to evaluate the effect of skele tal muscle mass on estimated glomerular filtration rate (eGFR) calculated by serum creatinine and cystatin C. Methods: From our kidney donor database, 601 donors were randomly selected in even distribution across age and sex. Skeletal muscle area (SMA) and skeletal muscle density (SMD) was extracted from the L3 level slice on predonation computed tomogra phy scan. Skeletal muscle index (SMI) was calculated by correcting SMA for height: SMA/height2. The association between the skeletal parameters and predonation eGFR with decreased eGFR ration at 6-month postdonation compared to predonation was analyzed by linear regression analysis. Results: Among the selected donors, skeletal muscle parameters were extracted from 592 donors. The skeletal muscle param eters were significantly different according to sex: SMA, 168.0±23.1 ㎠ vs. 109.4±13.8 ㎠; SMD, 45.2±5.2 Hounsfield units (HU) vs. 39.5±6.0 HU; and SMI, 57.0±7.2 ㎠/㎡ vs. 43.1±5.1 ㎠/㎡ (all P<0.001). All skeletal parameters were significantly associated with age, sex and body mass index. There was a significant correlation between predonation creatinine based eGFR and SMA and also SMI. No correlation was seen between skeletal muscle parameters and cystatin-based eGFR or DTPA (diethyl triaminopentaacetic acid)-measured glomerular filtration rate (GFR). SMA and SMI had negative correlation with the %change of creatinine based eGFR at 6-month postdonation in male donors but not in female donors. The association of %change of cystatin C based eGFR with all skeletal muscle parameters were not significant. Conclusions: Male kidney donors with high SMA or SMI are more likely to have decreased creatinine based eGFR after dona tion. This phenomenon is more likely associated with skeletal muscle mass rather than a reflection of true decrease in GFR. Cys tatin C based eGFR may reflect postdonation GFR more accurately in muscular male donors.