Many renal and urinary tract disorders may be asymptomatic for a long period of time. Routine urine screening programs are recommended as a basic fundamental step in early identification of renal damage. This has proved to be extremely important in reducing the growing burden of chronic kidney disease (CKD) in both developed and developing countries. To our knowledge, this is the first report on dipstick urine analysis screening among asymptomatic children in Lebanon.
Our findings of hematuria, proteinuria and nitrituria in school children were compared to other studies. The finding of urinary abnormalities was in nearly 2.1% of the studied group which was similar to the 2.5% and the 2.3% reported in Northern Iran and Malaysia respectively[10
]; higher than the 0.6% and the 0.72% reported in Tokyo and Egypt respectively[12
]; lower than the 7.2% and the 9.6% reported in Bolivian and Nigerian studies respectively[14
Hematuria was the most common abnormality found in our studied group. This was contrasted to other studies as in Egypt and Nigeria where proteinuria was the most common positive finding[13
]. The development of asymptomatic microscopic hematuria is relatively common in children. Its prevalence in school aged children has been estimated at 0.5% to 2.0% depending on the population screened. This was comparable to our results that showed a prevalence of 1.5% at the second screening (1.0% for isolated hematuria IH; 0.45% for combined hematuria and nitrituria CHN). Nigerian and Xiamen cities reported a prevalence of 1.5% and 1.21% respectively[15
]. On the other hand, hematuria had a lower prevalence in Malaysia, Egypt and Shanghai (0.21%, 0.36% and 0.46% respectively)[11
]. The finding of CHN was not reported previously.
The clinical significance of asymptomatic hematuria remains unclear and the merit of such an evaluation has not been confirmed. The child with persistent asymptomatic isolated microscopic hematuria of longer than 2 week duration poses a dilemma in regard to the degree of further diagnostic testing that should be performed. Based on medical recommendations, a child with persistent microscopic hematuria should be followed closely every 3 months and for one year[1
Bergstein et al evaluated 342 children referred to their nephrology clinic for asymptomatic isolated microscopic hematuria. Among these patients, they found no diagnosis in 274; hypercalciuria was the most common finding (16%); followed by membrano-proliferative glomerulonephritis (MPGN) and post-streptococcal glomerulonephritis (PSGN)[18
]. Other authors like Vehaskari et al performed biopsy samples from 22 children with microscopic hematuria having no family history of kidney disease and a negative evaluation for causation. Two children had IgA nephropathy and one child had Alport syndrome. The remaining biopsies were normal and showed non-specific focal tubular changes[19
]. In a screening done in Japan, they found 6 cases of IgA nephropathy and 7 cases of minor glomerular abnormalities among 220 children with asymptomatic hematuria[20
These studies showed that microscopic asymptomatic hematuria might be benign but it can also be an important sign of underlying disease. However, limitations of these studies were the absence of long term follow-up and thus, the frequency of development of complications and occult kidney disease was not known. Furthermore, it seems that in patients with microscopic hematuria due to occult glomerular disorders, progression to clinically significant disease will be accompanied by the development of hypertension with or without proteinuria or gross hematuria. Thus, long term follow-up in children with microscopic hematuria is mandatory[21
Another positive finding in our study was isolated nitrituria (IN) that accounted for 0.45% of the studied group at the second screening compared to the 1.5% in the Nigerian screening[15
]. Isolated nitrituria was not reported in other studies. Both the findings of IN and CHN could rise the suspicion of urinary tract infections although subjects were asymptomatic. Urinary nitrites are produced by bacterial breakdown of dietary nitrates. The reliability of the nitrite test for urinary tract infections has been investigated by several workers, most of whom concluded that false positive results were rare and that the test had a higher specificity for urinary tract infections[22
]. False positive results in general are explained by vaginal contamination or exposure of the dipstick to air for 1-2 weeks. Specificity of urinary nitrite test is about 98% (Rushton and long 2002). The sensitivity of the test has been reported to be low (21-59%) by some authors[23
] and high (80-93%) by others[25
]. One report in 1987 showed that urinary nitrite test detected 83% of asymptomatic urinary tract infections[24
Proteinuria can be a major cause of underlying kidney disease or a transient finding in normal children. In our study, first morning urine sample helped in excluding orthostatic proteinuria as a cause of isolated proteinuria in children The dipstick is sensitive to albumin mainly whereas quantitative methods detect all kidney proteins. Proteinuria is a strong independent and risk factor of end stage renal disease ESRD. Therefore, asymptomatic proteinuria warrants further work up to detect and even prevent ESRD[25
In this study, the proportion of students with proteinuria was 0.1% at the second screening. In Northern Iran and Nigeria, they reported that the prevalence of proteinuria was 1.6% and 3.5% respectively[10
]. These reports were higher than those of Tokyo and Egypt with a prevalence 0.08% and 0.12% respectively[12
In a screening done in Korea, renal biopsy was performed in 63.1% of children with IH, 10.5% of IP and 69.9% of combined hematuria and proteinuria. IgA nephropathy was the most common finding, followed by mesangial proliferative glomerulonephritis, Henoch-Shönlein nephritis, membranoproliferative glomerulonephritis and then lupus nephritis[26
Most positive findings were more common in girls than in boys in our screening.This was similar to the results of the Nigerian study[15
] but contrasted with the results of the Egyptian study which showed that age and sex had no impact in the results of the screening done[13
]. The finding of higher nitrites among females could be a reflection of higher rates of asymptomatic bacteriuria in the girls of the studied group,since nitrites are generated in urine by bacteria. Studies among school-age children have shown that bacteriuria is 30 times the prevalence among boys, attributed to the fact that girls have short urethra which predisposes them to ascending bacterial infection[15
Although the number of children and the number of females at age of 6 years were not higher compared to the other groups, we reported most positive results at this age group. Most abnormal urinary findings were found in North of Lebanon especially in the regions with poor socioeconomic status. This rises the question whether a correlation between chronic renal diseases and low social class could exist. In our screening, we did not perform other investigations as done by other groups. Most common causes of urinary abnormalities and the prevalence of kidney disease in Lebanon are still not yet known. If these causes are similar to those of previous studies done worldwide, this implies that early detection of these abnormalities could be of importance in improving the health of children.
A number of recommendations regarding urinary screening as part of well child care have been published by the American Academy of Pediatrics (AAP) over the past 20 year. In 1977 and 1992, the AAP recommended a screening urinalysis at 4 periods during a child's life. In 2000, the pediatric health care guidelines were revised to recommend a screening urinalysis at 5 years of age and during adolescence. In 2007, the screening urinalysis was removed altogether[28
]. However, urinalysis screening is still mandatory in many countries of Asia as in Japan, Taiwan and Korea. Therefore, it's clear that there's no global consensus as to whether screening for CKD should be undertaken in children. In Japan, the number of children and adolescents reaching ESRD decreased from 166 in 1984 to 86 in 2002. Also, Murakami et al compared the situation in Japan and the United States. The number of children starting ESRD therapy is 6 per million in Japan compared with 30 per million in the United States[6
]. It is particularly important that the prevalence data for CKD in children worldwide should be updated and additional evidence should be obtained on whether effective interventions will reduce the number of children with ESRD.
From the above statement, it is evident that there's difference in data between Asia and United States. Lebanon is one of the developing countries of Asia with poor socioeconomic status and poor education in its periphery where routine visits to pediatricians are infrequent. This reinforces the necessity of screening children at school entry by dipstick urine analysis.