P569 - DOES A FULL BLADDER MATTER? DIFFERENCES IN BODY COMPOSITION, USING BIOELECTRICAL IMPEDANCE BEFORE AND AFTER URINATION.

P569

DOES A FULL BLADDER MATTER? DIFFERENCES IN BODY COMPOSITION, USING BIOELECTRICAL IMPEDANCE BEFORE AND AFTER URINATION.

G. E. C. Slager^1,2,*, I. H. Visscher², M. M. Peters², A. S. Niemeijer³, M. K. Nieuwenhuis^1,3,4, M. J. Sealy¹

¹Research Group Healthy Ageing, Allied Health Care and Nursing, ²Department of Physiotherapy, Hanze University of Applied Sciences, ³Alliance of Dutch Burn Care, Burn Center, Martini Hospital Groningen, ⁴Department for Human Movement Sciences, University of Groningen, University Medical Center Groningen, Groningen, Netherlands

Rationale: In bioelectrical impedance analysis (BIA) measurements, standard protocol often indicates to measure after urination, which is time consuming, especially in immobile patients. Therefore, this study examines whether body composition measured with BIA differs before (full bladder; FB) and after urination (empty bladder; EB). 

Methods: BIA measurements were performed with the Bodystat-500. Young Adults were measured with BIA, three times with a FB and three times with an EB. Fat-free mass FFM was calculated with Kyle’s formula and fat mass FM as FM= FFM – weight. Mean values (+/-SD) of each three measurements and the mean change (∆) in FFM and FM between FB and EB were calculated. Mean changes were compared with a paired samples t-test (p<0.05*)

Results: Sixty-nine healthy Caucasian participants (32 male, 37 female) participated: median age 22 (IQR 21-24) years;  mean BMI 23.7 (+/- 2.4) kg/m². Their median urine production was 450 (IQR 338-603) ml; median ∆ weight FB – EB: 0.50 (IQR 0.30 – 0.70) kg. Mean changes in FFM were significant, but minimal: 0.10 +/- 0.30 kg (p=0.009*), while mean ∆FM showed clinically relevant and significant differences: 0.46 +/- 0.40 kg (p<0.001*). If the EB bodyweight is used in all calculations, this results in a small, non-significant mean ∆FFM and ∆FM: both 0.03 +/- 0.27 kg (p=0.344).

Conclusion: This study demonstrates that BIA measurements can be performed without urination, if EB weight is used in the formulae. In practice, one could measure weight at one time point, for instance in the morning after toilet use. Subsequently, this EB weight can be used and measure body composition with BIA at any time of the day independent of a full bladder. 

Disclosure of Interest: None declared