This study was designed to assess resting energy expenditure (REE) and nutritional status in children with hepatic and prehepatic portal hypertension in comparison with healthy controls. Twenty-five patients with portal hypertension (PHT) and a history of variceal bleeding were compared with 14 healthy volunteers selected after matching for age and sex. PHT patients were allocated to one of two groups: 11 children with liver cirrhosis and/or chronic hepatitis, aged 14.0 +/- 3.3 y (means +/- SD) or 14 children with extrahepatic portal vein obstruction, aged 12.3 +/- 2.8 y. The control group consisted of 14 healthy children, aged 14.0 +/- 1.8 y, REE (indirect calorimetry) assessed after an overnight fast was significantly higher in PHT patients than in controls when related to body mass (143.7 +/- 29.5 and 116.1 +/- 5.9 kJ/kg, respectively; p < 0.004), lean body mass (168.0 +/- 28.9 and 146.4 +/- 14.1 kJ/kg, respectively; p < 0.02), and body surface area (7480 +/- 736 and 6590 +/- 567 kJ/1.73 m(2), respectively; p < 0.001). The ratios of measured REE to, basal energy expenditure calculated from standard equations (Schofield equations) indicated higher REE in PHT patients (102.24 +/- 6.90% and 93.54 +/- 4.47%, respectively; p < 0.001). Fat was the predominant source of energy in both PHT patients and controls; the percentage of nonprotein energy derived from carbohydrate oxidation was equaled: 36.04 +/- 18.84% and 37.15 +/- 15.71%, respectively. Analysis of percentage of undernutrition in PHT patients and controls revealed significant differences (44% and 21%, respectively; p < 0.001). Children with PHT are susceptible to malnutrition and have elevated REE compared with healthy controls. Fat is the principal basal state oxidative substrate for patients with PHT and healthy children.