Urinary metabolic abnormalities in children with idiopathic hematuria.

BACKGROUND

Hematuria, either macroscopic or microscopic, is an incidental finding of multiple nephrologic or urologic disorders. Disturbances of urine inhibitors or promotors have been suggested as the potential causes of isolated idiopathic hematuria in children and its recurrence. Meanwhile, appropriate treatment of these risk factors might improve secondary asymptomatic or macroscopic hematuria.

OBJECTIVES

The aim of this study was to identify contribution of urinary biochemical abnormalities in children with isolated idiopathic hematuria.

METHODS

About 522 children with isolated hematuria were evaluated in a prospective cross-sectional study. Data such as clinical manifestations, family history, laboratory examinations, structural anomalies, and urine biochemistry were obtained. Patients with nephrolithiasis, nephrocalcinosis, tubulointerstitial disorder, genitourinary abnormality, urinary tract infection, and glomerular disorder were excluded from the study. Variables such as calcium, citrate, oxalate, phosphate, uric acid, cystine, and magnesium were measured in 24-h urine collection. In addition, serum levels of electrolytes, urea, creatinine, parathyroid hormone, and bicarbonate were identified.

RESULTS

Mean age at diagnosis was 5.9 years, and females outnumbered males (2/1). Of those, 88.5% had microscopic hematuria, and 12.6% experienced episodes of gross hematuria. Abdominal pain was the most common clinical manifestations. Urinary tract infection occurred in 30% of cases. Totally, 94% of patients had single or multiple metabolic abnormalities in 24-h urine excretion including hypocitraturia, 60.7%; hypomagnesuria, 58.2%; hyperuricosuria, 35.8%; hypercalciuria, 33.7%; hyperoxaluria, 33.7%; and cystinuria, 0.76%, respectively. About 8% of cases had mixed urine metabolic disturbances. Most patients had mild hematuria (red blood cell <10/high power field (hpf)), and 18% had significant hematuria (>30/hpf), with no statistical correlation to urine metabolic abnormalities. About 80% of patients had a history of nephrolithiasis in their relatives.

DISCUSSION

Decreased urinary inhibitor concentration followed by increased stimulator concentration were the most common abnormalities in patients with idiopathic hematuria. Accordingly, measurement of urinary biochemical concentration is highly recommended in children with isolated hematuria. In addition, investigating the therapeutic effect of potassium citrate supplements is highly recommended in these patients to prevent future stone formation and treatment of hematuria.