Inferior vena cava diameter: a useful method for estimation of fluid status in children on haemodialysis

BACKGROUND: An accurate assessment of fluid status in haemodialysis patients presents a significant challenge especially in growing children. Clinical parameters of hydration are not always reliable, and invasive methods such as measurement of central venous pressure cannot be used routinely. We evaluated the usefulness of inferior vena cava diameter (IVCD) measured by echocardiography in the estimation of hydration in children on haemodialysis. METHODS: Fifteen haemodialysis patients (mean age 14 years) were evaluated. Clinical assessment included patients' symptoms, weight, blood pressure, heart rate, presence of oedema and vascular congestion, before and after dialysis session. Dry weight was assessed based on the above parameters. Fifty-two echocardiographic studies immediately prior and 30-60 min following dialysis were performed. The anteroposterior IVCD was measured 1.5 cm below the diaphragm in the hepatic segment in supine position during normal inspiration and expiration. IVCD was expressed per body surface area. RESULTS: Following haemodialysis mean IVCD (average of expiration and inspiration) decreased from 1.12+/-0.38 to 0.75+/-0.26 cm/m(2) (P<0.0001). Changes in IVCD were significantly correlated with alterations in body weight following dialysis (P<0.0001). The collapse index (per cent of change in IVCD in expiration vs inspiration) increased significantly after dialysis (P=0.035). IVCD clearly reflected alterations in fluid status. It did not vary significantly with changes in dry weight in a given patient. CONCLUSIONS: Our findings support the applicability of VCD measurement in the estimation of hydration status in paediatric haemodialysis patients. The combination of clinical parameters and measurement of IVCD may enable more accurate evaluation of hydration of children on haemodialysis.