- Renal scarring associated with intrarenal reflux of infected urine (ie, acquired reflux-associated nephropathy).
- Congenital nephropathy associated with vesicoureteral reflux (VUR) but in the absence of infection.
- Nephropathy associated with VUR and impairment of urinary flow (ie, secondary VUR).
Acquired Reflux Nephropathy
It is estimated that the general incidence of primary VUR in the population is 0.4–1.8%. In children who present with a febrile urinary tract infection (UTI), the incidence of VUR increases significantly to 12–50%. Approximately 30–60% of children with VUR will have established renal scars at the time of diagnosis. Moreover, 12% of children with VUR and normal kidneys will develop scarring, irrespective of medical or surgical management. In young children, acquired reflux nephropathy is more common in girls than boys, with a ratio of 4 to 1, similar to the sex prevalence in patients with VUR detected after evaluation for a UTI. In older children, the incidence of reflux nephropathy is equivalent among the sexes, but males appear to be more severely affected. In adults, bilateral nephropathy is more common in men than in women.
Congenital Reflux Nephropathy
With the advent of routine prenatal ultrasonography, many children with VUR are detected prior the development of a UTI. It is estimated that the incidence of VUR in patients with prenatally diagnosed hydronephrosis is approximately 15–20%. In contrast to the sex prevalence of VUR diagnosed following a UTI, VUR detected during evaluation for prenatal hydronephrosis is more common in boys than in girls. It is estimated that 30–50% of these children will have renal abnormalities such as decrease in size, dysmorphic features, or imaging findings similar to renal scarring. The degree of renal abnormalities correlates with the increasing severity of the reflux.
Overall Incidence of Renal Abnormalities
Whether VUR is diagnosed following a UTI or in the evaluation for prenatal hydronephrosis, renal abnormalities/scarring are common at the time of diagnosis. Reflux nephropathy was found to be present in 27% of patients with VUR at the time of presentation. Of children less than 1 year of age, 20% had diffuse abnormalities while 5% had focal abnormalities. In children 1–5 years of age, the same percentage of patients had diffuse abnormalities but 16% had focal abnormalities. Similarly, in children older than 5 years of age, the number of patients with diffuse renal abnormalities was constant at 18% but 20% had focal abnormalities. Dysmorphic kidneys were more commonly seen in children younger than 1 year of age at the time of evaluation, while focal scarring was more commonly seen in older children. In children younger than 1 year of age the male to female ratio with reflux nephropathy was 1.6:1. In contrast, the ratio of male to female changed to 1:4 in older children.
The risk of scarring is greatest in children younger than 1 year of age; reflux nephropathy occurs ...