RESUMO
OBJECTIVE: The kidney of the child, mainly the newborn, is specially susceptible to ischemic and/or toxic injuries, which can affect the renal tubular function. Therefore, reliable and precocious markers of tubular dysfunction would be useful in Pediatrics. The urinary levels of retinol binding-protein (RBPu) has been used in this way. Our goal was to evaluate the RBPu behavior in childhood to establish a reference interval and verify possible differences according to the age. METHODS: We studied healthy children aged 1 month to 8 years and healthy term and preterm babies; in the last group we only included babies without hemodynamic repercussion. We collected isolated urine samples once for children above 1 month and periodically for those below this age. In this urine, besides the dipsticks test (Combur 9(R), Boehringer), RBPu and creatinine were measured. RESULTS: We observed that the RBPu levels in childhood do not have a normal distribution; after logarithm data transformation we were able to establish an interval of reference for children above one month of age: 3 to 269 micro g/L, mean of 27 micro g/ L. In newborns, we found a large variation of RBPu excretion. However, we noticed that the excretion decreases significantly, reaching the healthy adult levels at the end of the 1st month, for term as well as for preterm newborns. CONCLUSIONS: We suggest that RBPu can be used as a marker of proximal tubular dysfunction, since we could establish an interval of reference, and it can be repeated whenever necessary in the follow-up of this kind of injury, because it is not an invasive exam. Moreover, this study contributes to the knowledge of the tubular function development for showing that at the end of the 1st month of life the newborn's kidney is able to reabsorb RBPu as the healthy adult kidney is.
RESUMO
OBJECTIVE: To evaluate the diagnostic frequency of the various diseases associated with the development of hematuria in children, in a pediatric nephrology unit pertaining to a university hospital. METHODS: The clinical records of 128 children (70 male, 50 female) who presented intermittent/persistent macroscopic hematuria or persistent microscopic hematuria as the chief clinical complaint/finding, in the period of 1978-1995, were retrospectively analyzed. This evaluation was performed with special attention to the patientacute;s clinical history, physical examination, personal and family morbid history information. Patients whose investigation was not complete were not considered for analysis. The mean age on presentation was 8.2 years (5 months - 16 years) and the mean period of observation was 3.2 years (1 month-15 years). RESULTS: Macroscopic hematuria occurred in 104 patients and persistent microscopic hematuria was present in 24 patients. Urinary metabolic disturbances and urinary lithiasis, alone or in association, were diagnosed in the majority of the patients (65.5%). Hypercalciuria was the urinary metabolic disturbance (90.1%) mostly detected, either alone (73.2%) or in association with hyperuricosuria (16.9%). A positive family history of lithiasis was reported in 32.1% of the patients in which the diagnosis of lithiasis/urinary metabolic disturbance was confirmed. Glomerulopathies were diagnosed in 25% of the patients, with the predominance of post-infectious acute glomerulonephritis (11 patients, 34%). In 6 children, the etiology of hematuria was not elucidated, despite extensive investigation, including renal biopsy.CONCLUSION: The authors present an algorithm for the diagnosis of hematuria in children and suggest that in cases of isolated hematuria, presenting without clinical clues to the possible etiology, laboratory investigation should be started with the evaluation of urinary metabolic disturbances / lithiasis.