Different methods have been proposed as possible indicators of nutritional status in renal patients. The measurement of the electrical impedance of the body (BIA) is a simple, and inexpensive method to analyze body composition and body fluid compartments. BIA allows to estimate Fat Free Mass (FFM) and Body Cell Mass (BCM). BCM is mainly related to muscle mass.
Aim of this study was to validated the measurement of BCM obtained with single and multifrequency BIA as an indicator of the amount of muscle mass.
Creatinine (Creat) is produced by muscle cells and is excreted almost exclusively by the kidneys. Therefore, at steady state, 24 hour urinary creatinine excretion (24h UCr) equals creatinine production and is a useful tool to assess the amount of muscle mass.
Patients and methods
Sixty-two adult renal patients (29 F, 33 M) aged 19-79 years, affected by different kidney disease, with different kidney functional impairment participated in this study. Their serum creatinine ranged between 0.55 and 2.27 mg/dL and GFR (clearance of 99mTc-DTPA) between 32 and 127 mL/min/1.73 m2..
The values of BCM were obtained using a single frequency and a multifrequency tetrapolar impedance plethysmograph tetrapolar.
Patients were instructed to collect 24 hour urine. Urine were collected for two days within a week and urine volume was recorded. Urinary creatinine was measured with standard auto-analyzer methods and 24 hour urinary creatinine excretion (24h Ucr) was calculated.
A very high linear correlation was found between the values of BCM and 24h Ucr (r=0.807) [Figure 1].
These data indicate that the value of BCM obtained with BIA is strictly related to the amount of muscle mass, estimated from 24h Ucr.
In conclusion, the measurement of electrical body impedance, which allows to estimate body cell mass, seems an adequate tool to evaluate muscle mass and thus nutritional status of renal patients.