Efficacy of measuring BUN in assessing children with dehydration due to gastroenteritis

We conducted a prospective study of 50 consecutive cases of children with gastroenteritis and dehydration to assess the correlation of alterations in the blood urea nitrogen (BUN) concentration. Symptoms included 24 children with vomiting and 26 with vomiting and diarrhea. All children were estimably dehydrated-appearing on examination by traditionally used criteria and had metabolic acidosis (serum bicarbonate concentration of less than 20 mEq/L) and increased anion gap (more than 12 mEq/L). Of these 50 children, 44 (88%) had a BUN concentration within the limits of normal - 17 were less than or equal to 10 mg/dL, 17 were between 11 and 14 mg/dL, and ten were between 14 and 18 mg/dL. We discuss the physiologic factors that influence the BUN concentration in conditions of dehydration. Although commonly used, measurement of the magnitude of the BUN concentration is not an accurate method for assessing the hydration status of children with dehydration due to gastroenteritis.