187
finding has been consistently reported in many series of VUR detected 166 by
investigation of prenatal hydronephrosis.
Recently, we reported a survey of 11 series of fetal reflux in which there
was a 5:1 predominance of boys.
13
This fact was also observed by Yeung et al.
23
in the largest series reported thus far, in which 155 neonates were studied, 117
(75%) of them males. Some hypotheses have been raised to explain these
findings. VUR may be underestimated in boys due the low incidence of urinary
tract infections in this group.
24
The presence of a transient bladder outlet
obstruction in utero isanother hypothesis.
25
Anderson and Rickwood
11
suggested
that a high intrauterine micturitional pressurein male fetuses might distort the
ureterovesical junction, causing reflux and renal damage. In our study, there was
renal damage in 40% ofthe children and in 26% of the renal units evaluated at
admission.
There was a significant association between renal damage and the
method of investigation, the age of diagnosis of the VUR, the grade of reflux and
the gender. In our study, the prevalence of renal damage was influenced by the
method ofinvestigation used to evaluate the occurrence of renallesion. The
selection of the method of investigation was determined by two factors, or, the
period of admission to our unit and the severity of reflux. IVP was almost the only
option until the mid-eighties and was applied to most of the patients (68%). After
1990, the selection of the method of investigation was based on the severity of
reflux mainly due to the limitation of public health resources. Thus, the DMSA scan
was reserved to patients with severe reflux and those with mild reflux were
frequently submitted only to ultrasonography. Our data show that the DMSA scan
had almost three times the chance to reveal renal scars (OR = 2.8, p < 0,001) and
this difference was even greater for mild/moderate reflux. A study carried out to
compare the accuracy of the three methods used to detect scarred kidneys
showed that the sensitivity of DMSA scan, IVP, and US was 94%, 76%, and 65%,
respectively.
26
Therefore, we are aware that this fact could underestimate the
presence of renal scars, especially localized or small ones. Nevertheless, the
prevalence of renal damage at baseline was similar tothat found in other studies.
Smellie et al.
4
reported a prevalence of 25% to 46%, varying according to theage
at the time of entry in the study.
Recently, Howardet al.
27
compiled several series of VUR from different
geographical locations and demonstrated that the prevalence of renal scarring
ranged from 27% to42%. We found a greater proportion of affected units in the
extreme ages of diagnosis (neonatal or older than six years). In the group
identified by fetal hydronephrosis, 50% of the units presented with renal damage
at 167 diagnosis. Recently, in a series of 93 infants, Lama etal.
10
reported that
renal damage was present in 85% of the refluxing units in the group of prenatal
diagnosis and in 63% of those diagnosed after urinary infections. The group of
children in which reflux was diagnosed after two years of age had a 50% greater
chance ofrenal damage at baseline (OR = 1.5, p = 0,01). The still small proportion
of “fetal” reflux in our series, the group with the highest incidence of renal damage,
could probably explain this finding.In our series there was a strong association
between renal damage and severe grade of reflux. The relationship between the
degree of reflux, the occurrence of renal scars and the severity of damage has
also been described by other authors.
Skoog et al.
21
reported an increasing prevalence of renal scars with the
degree of reflux: 5% in grade I, 6% in grade II,17% in grade III, 25% in grade IV,