[Proteinuria in urinary infection and acute pyelonephritis in paediatric patients: can it replace scintigraphic studies in diagnostic localisation?]

Abstract

ANTECEDENTS AND OBJECTIVES: The location of the urinary tract infection in children has serious implications both in therapy and prognosis. Affectation in gammagraphic studies is considered the "gold standard" for the diagnosis of acute pyelonephritis. Several studies with biomarkers have been made with controverted results. The objective of this study is to set the utility of beta2-microglobuline, alfa1-microglobuline, Cistatine C, IgG and albumin in the location of the infection, through the analysis of the relation among their urinary excretion, clinical and laboratory parameters and the renal scintigraphy findings.

Patients and methods: Prospective observational study made in 40 patients, aged from 1 month to 11 years, after their Hospital admission with suspicion for acute pyelonephritis. Exclusion criteria were: decrease in the glomerular filtration rate, malnutrition, massive albuminuria and history or findings of nephrourologic disease. Clinical and laboratory variables were analyzed, and renal ultrasonography and scintigraphy were performed within the first seven days after admission. Once the fever dropped, the urinary creatinine-protein ratio was analyzed. After the acute process, a renal scintigraphy was performed in order to detect renal scars. The non-parametric Mann-Whitney U test has been used as the statistical hypothesis test, and Chi-square and Fisher s exact tests have been used to compare the qualitative variables.

Results: The glomerular filtration rate, as well as the ultrasonography scan, was normal in all patients. 45% of the children (24/80 kidneys) had scintigraphic alterations that were compatible with acute pyelonephritis, and there were not differences in proteinuria between these and those with normal scintigraphy. To greater age greater probability of scintigraphic affectation. The sensitivity and specificity of leukocytes and CRP to predict pyelonephritis were 77-65% and 94-52%, r = 0.70 (CI 95% 0.54-0.87) y 0.75 (CI 95% 0.60-0.90) respectively. An apparent relation between the maximum temperature or duration of the symptoms and the renal affectation does not exist. In all the children, the normality of urinary markers of renal function was confirmed once the acute phase had passed, even in those 3 patients with renal scars (7.5%).

Conclusions: Renal scintigraphy is still being the reference pattern for the diagnosis of acute pyelonephritis in Pediatrics. The combined use of different urinary markers of renal function does not increase its sensitivity. It is necessary to do research in order to confirm the utility of new biomarkers.