Fetal vesicoureteral reflux

Vesicoureteral reflux

Vesicoureteral reflux (VUR), the retrograde flow of urine from the bladder toward the kidney, is common in young children. About 30% of children with urinary tract infections will be diagnosed with VUR after a voiding cystourethrogram. For most, VUR will resolve spontaneously; 20% to 30% will have further infections, but few will experience long-term renal sequelae. Developmentally, VUR arises from disruption of complex signaling pathways and cellular differentiation. These mechanisms are probably genetically programmed but may be influenced by environmental exposures. Phenotypic expression of VUR is variable, ranging from asymptomatic forms to severe renal parenchymal disease and end-stage disease. VUR is often familial but is genetically heterogeneous with variability in mode of inheritance and in which gene, or the number of genes, that are involved. Numerous genetic studies that explore associations with VUR are available. The relative utility of these for understanding the genetics of VUR is often limited because of small sample size, poor methodology, and a diverse spectrum of patients. Much, if not all, of the renal parenchymal damage associated with end-stage disease is likely to be congenital, which limits the opportunity for intervention to familial cases where risk prediction may be available. Management of children with VUR remains controversial because there is no strong supportive evidence that prophylactic antibiotics or surgical intervention improve outcomes. Furthermore, well-designed genetic epidemiological studies focusing on the severe end of the VUR phenotype may help define the causal pathway and identify modifiable or disease predictive factors.

Does treatment of vesicoureteric reflux in childhood prevent end-stage renal disease attributable to reflux nephropathy?

OBJECTIVE

It is believed that end-stage renal disease (ESRD) attributable to reflux nephropathy is preventable by the active treatment of vesicoureteric reflux in childhood with long-term antibiotics and ureteric reimplantation surgery. We aimed to test this belief.

METHODOLOGY

The Australia and New Zealand Dialysis and Transplant Registry of new patients 5 to 44 years of age treated for ESRD between 1971 and 1998, categorized by age and primary renal disease, was used to analyze the age-specific incidences of ESRD attributable to reflux nephropathy using a before-after study design. The early 1960s were regarded as the introduction period for the active treatment of childhood vesicoureteric reflux. A time-delay in treatment effect was expected. Patients with ESRD attributable to other causes were used as a comparative group.

RESULTS

The incidence of ESRD attributable to reflux nephropathy and nonreflux nephropathy has increased. For reflux nephropathy, the rate of change was significantly associated with age, with a downward trend in incidence with decreasing age suggesting a minor treatment effect. This trend was no longer evident when adjustment was made for changing diagnostic practices. An opposite trend was observed for the nonreflux nephropathy group, who demonstrated an upward trend in incidence with decreasing age.

CONCLUSIONS

Treatment of children with vesicoureteric reflux has not been accompanied by the hoped-for reduction in the incidence of ESRD attributable to reflux nephropathy. A randomized trial with a control (no-treatment) arm is required to appropriately assess the medical belief that long-term antibiotics and surgery improve the natural history of vesicoureteric reflux.

Vesicoureteric reflux and renal injury

Renal injury associated with the intrarenal reflux (IRR) of urine that is either infected, under high pressure, or both, is a major cause of severe hypertension during childhood and adolescence and of chronic renal insufficiency in patients less than 30 years of age. Many, but not all, adolescent and adult patients with reflux nephropathy (RN) give a history of urinary tract infection (UTI) or unexplained fevers in infancy or early childhood, when the kidney is thought to be at greatest risk of injury. Although vesicoureteric reflux (VUR) is observed more commonly in infants than children with UTI, it is rare in uninfected patients at any age and should never be considered a normal finding during human development. Renal scarring may not be obvious in radiographic or radionuclear studies to medical management alone, no definite benefit of one over the other was observed, regardless of the grade of VUR. Moreover, progressive renal injury in scarred kidneys has been noted even after VUR had been corrected, when infection had been prevented, and while hypertension had been controlled satisfactorily. Focal glomerular sclerosis, a lesion found in patients with proteinuria and RN, has been identified not only in scarred kidneys, but also may be seen in contralateral, unscarred kidneys without VUR, which might suggest a humoral factor or, perhaps, a hyperfiltration phenomenon. RN is one of the most frequent causes of end-stage renal disease (ESRD) in children, adolescents, and young adults, which is potentially preventable. However, prevention will depend on early identification of patients at risk--infants and young children after the first UTI and siblings of patients with VUR--aggressive and effective treatment of UTI, minimizing intravesical pressure, and education of patients, parents, and physicians.

Evolution of renal segmental atrophy (Ask-Upmark kidney) in children with vesicoureteric reflux: radiographic and morphologic studies

A radiographic and morphologic study of nine patients with renal segmental "hypoplasia," whose kidneys were radiographically normal when first examined, showed the lesion to be a form of localized, progressive renal atrophy. The renal abnormality bears a strong relationship to vesicoureteric reflux, which could be demonstrated in every patient. No evidence of renal scarring or atrophy was observed in initial roentgenographic examinations at a mean age of 2.9 years (range 0.1 to 10 years); however, serial studies during five to 14 years after discovery of vesicoureteral reflux demonstrated both a lack of renal growth and a progressive loss of substance irrespective of infection. Radiographic lengths of scarred kidneys, as measures of renal growth, correlated poorly with the radiographic surface areas of the renal parenchymal outlines. The mean time from discovery of vesicoureteric reflux to appearance of a renal scar was 6.1 years, and to onset of hypertension in six patients was 7.8 years. The renal abnormality consisted of lobar atrophy with variable tubular atrophy and glomerular sclerosis and with parenchymal destruction that in some specimens had proceeded to a complete loss of nephronic elements. The occasional presence of relatively well-preserved glomeruli and tubules and of focal segmental sclerosis within persisting glomeruli was taken as evidence of a progressive renal abnormality, as opposed to a static developmental hypoplasia. These observations indicate that renal scarring, the injury presumably having been initiated by vesicoureteric reflux, can progress despite correction of the reflux and despite prevention of urinary tract infection.