Impaired acidification of urine in children aged two months to two years with acute gastroenteritis complicated by acidosis

Abstract

In some children with acute gastroenteritis and acidosis, the urine pH may be abnormally high thus simulating distal Renal Tubular Acidosis (dRTA). This inability to acidify urine properly in the presence of metabolic acidosis has been shown to be due to poor delivery of sodium to the distal nephron which prevents full excretion of a hydrogen ion load, instead of an intrinsic defect in the ability of the distal tubule to acidify urine. The aim of this study is to determine the prevalence of transient urinary acidification defect in children aged two months to two years with acute gastroenteritis, dehydration and acidosis, and the relationship between urine pH and urine sodium concentration. A prospective study of children aged two months to two years admitted for the treatment of acute gastroenteritis and dehydration at the Children's Emergency Ward (CHEW) of the University of Port Harcourt Teaching Hospital, Rivers State. Of the 196 children (140 males and 56 females) studied with spontaneous acidosis which developed as a result of acute gastroenteritis, seventy-three of them had impaired acidification of urine, giving a prevalence of 37.2%. There was no significant difference in the age, duration of symptoms, degree of acidosis, degree of dehydration and serum potassium concentration between the children with impaired and those with proper urine acidification. Those with impaired acidification of urine however had a significantly lower serum sodium and urine sodium concentrations and a significantly higher urine potassium concentration and urine anion gap than those children with proper urine acidification. All urine samples with sodium concentration less than or equal to 25 mmol/L (52) had urine pH greater than 5.5. Mere presence of acidosis and high urine pH should not lead to a diagnosis of Distal Renal Tubular Acidosis (dRTA). The urine anion gap (UAG) should be calculated using the formula: urine [Na+] + [K+] [Cl], and if negative, it suggests a high ammonium excretion, which makes the diagnosis of dRTA unlikely.