Genetic Study And Imageological Examinations Evaluation Of Primary Vesicoureteral Reflux

Genetic study and imageological examinations evalution of primary vesicoureteral refluxPrimary vesicoureteral reflux (VUR) is characterized by the retrograde flow of urine from the bladder to the ureters and kidneys.This congenital anomaly of kidney and urinary tract (CAKUT) affects about 1%-2% of young children and is thus one of the most common congenital anomalies affecting humans. Primary VUR is thought to be associated with dysfunctional vesicoureteric junction. Individuals with VUR are prone to recurrent urinary tract infections (UTI); indeed, 30% to 40% of children presenting with such infections have primary VUR. According to the degrees of severity, VUR is graded fromⅠtoⅤ. GradeⅠandⅡare grouped together as low grade VUR, and gradeⅢtoⅤas high grade. Some children with primary VUR may resolve spontaneously with age. However, the probability of spontaneous resolution for high-grade VUR is rather low, and high grade is more likely to cause renal damage. The reflux of infected urine into the kidney can cause acute pyelonephritis and subsequent renal scarring; such "reflux nephropathy (RN)" has association with sustained hypertension in adult, and is an important cause of end-stage renal disease (ESRD) in children.Primary VUR has a strong hereditary component. In recent 30 years, foreign countries have already embarked on a large number of scientific researches on VUR, with the aim of finding predisposing genes, which may disclose the pathogenesis at gene level, and will be useful for early identification of children with high risk factors. Nevertheless, there is no consensus so far on the gene causing disease because of the racial diversifies and genetic heterogeneity of primary VUR.Until now there are few reports on genetic research of primary VUR in our country. With the objective of investigating the genetic contribution of UpⅢ, Robo2 and Ret to primary VUR in pediatric patients of China, identifying whether mutational sites of these genes reported in recent studies also exist in our patients, we conducted this study. Sequencing analysis was performed on DNA samples from 50 primary VUR patients. The sequencing of all exons of Up III revealed 12 single-nucleotide polymorphisms (SNPs), of which G466>C in the 3rd exon causes missense change. However, the allele C frequencies of patients' and controls' were not different significantly (76% vs 73%, P>0.05). The sequencing of exon 7,11,12,15, 16,23 of Robo2 showed only 2 SNPs in introns regions. And the sequencing of the 11st exon of Ret demonstrated 2 SNPs, of which only 2261 G>A causes missense change. However, the frequency of the allele A of patient group did not differ significantly from that of controls (14% vs 13%, P>0.05). Therefore predisposing gene loci of primary VUR were not found this time, but we are clear about the distribution of SNPs of these genes, which may be helpful for further genetic studies.The gold standard technique for diagnosing and grading of primary VUR now is micturating cystourethrography (MCU), which has been widely accepted all over the world. For children presenting with febrile or recurrent UTI, especially those younger than 2 years, MCU should be considered to perform after UTI to identify whether VUR exists. Nevertheless this examination is often rejected by parents because of its invasiveness, exposure of babies to radiation and risk of reinfection. To avoid performing this examination, foreign experts have already investigated and discussed a lot. Alternative method which is convenient and noninvasive is badly needed.99mTc-DMSA (DMSA) renal scintigraphy is the gold standard technique for detecting parenchymal lesions from both APN and renal scars. In the initial stage of acute phase, renal lesions can be detected by DMSA exactly by observing the absorption of 99mTc. This imaging method is also widely used in febrile UTI children. At acute phase, it offers great value in distinguishing pyelonephritis from lower UTI, thus is very helpful for guiding the usage of antibiotics. As UTI children with VUR are more likely to affect kidneys, we speculated that primary VUR could also be predicted by DMSA while detecting renal damage.To evaluate the efficacy of acute DMSA scan in predicting VUR, and investigate the priority of applying between MCU and DMSA for febrile UTI, medical and radiologic records of children (≤2 years) with febrile UTI between January 2000 and December 2009 were retrospectively reviewed. All included children must have undergone acute DMSA renal scanning and MCU. Based on the results of MCU, patients were grouped as non-VUR, low-grade VUR (Ⅰ-Ⅱ) and high-VUR(Ⅲ-Ⅴ).A total of 370 young children (233 boys,137 girls) were included, of which 263 (71.1%) had abnormal DMSA results and 126 (34.1%) were identified as primary VUR on MCU. Among children with VUR, the number of high-grade was 103 (81.7%). The rate of abnormal results on DMSA of high-grade VUR group was significantly higher than the rates of the other two groups (P<0.01). Therefore, high-grade VUR is an important risk factor of renal damage for young children with febrile UTI.It was found that the sensitivity of DMSA for detecting high grade VUR was 99.0%. The negative predictive value and negative likelihood ratio were 99.1% and 0.03, respectively. According to these figures, it could be concluded that the possibility of detecting high-grade VUR on MCU is rather low when the result of DMSA is negative. So DMSA is not only the gold standard technique to detect renal lesions, but also could predict the majority of children with high-grade VUR. We recommend DMSA should be used before MCU to investigate the febrile UTI children at acute phase. Applying the conclusion to the children included in this study, 107 would obviate MCU examination as only 1 child with grade IV was missed.In conclusion, this is the first study on genetics of primary VUR of our country. The association of candidate genes UpⅢ, Robo2 and Ret with primary VUR was investigated respectively. Predisposing gene loci were not found this time, but we are clear about the distribution of single nucleotide polymorphisms of these genes in primary VUR patients, which may be helpful for further genetic studies. In the second part, by retrospectively reviewing the medical records of recent 10 years, we evaluated the efficacy of DMSA in predicting vesicoureteral reflux (VUR) among young children with febrile UTI. As a result, it was found that DMSA could predict the majority of children with high-grade VUR with high sensitivity. Thus DMSA is recommended to be performed before MCU to investigate febrile UTI children at acute phase. This finding provides theoretical evidence for clinical option of imaging examinations.