Outcome of primary vesicoureteric reflux detected following fetal renal pelvic dilatation.

OBJECTIVE: Postnatal investigation of mild degrees of fetal hydronephrosis has allowed subsequent detection of infants with vesicoureteric reflux (VUR). This study was designed to provide short to medium term information on such infants who had primary VUR, the rates of renal damage and progression over time, the risk factors for such damage and to compare the characteristics of those who had mild dilatation of the fetal renal pelvis (4-9 mm) with those who had moderate-severe dilatation (> or = 10 mm).

METHODOLOGY: Since June 1989, infants whose antenatal sonography had identified a fetal renal pelvis with an anteroposterior diameter of > 4 mm were investigated postnatally with renal ultrasonography and micturating cystourethrogram (MCU), and placed on antimicrobial prophylaxis. Those with VUR received 99mTc-dimercaptosuccinic acid (DMSA) scintigraphy. Infants were followed until discharge based on resolution of VUR, surgery, or low grade VUR. A 5.5 year cohort between June 1989 and December 1994 formed the study population. A review of notes and clinical review (if still under follow up) was undertaken. Vesicoureteric reflux on MCU was regraded according to the International Classification, and reflux nephropathy on DMSA scans was regraded according to criteria proposed by Goldraich. Regression analysis was used to assess risk factors for renal damage.

RESULTS: There were 69 infants (37 girls, 32 boys) who were identified with primary VUR, with 37/69 having bilateral reflux. Eight had a urinary tract infection during the follow-up period. There was a broad distribution of grades of reflux detected (Grades I-3, Grades II-23, Grades III-19, Grades IV - 17, Grades V-7). 99m-Tc-dimercaptosuccinic acid scans on 57/69 (83%) demonstrated renal damage in eight infants (14%). This was predominantly global contraction of function. No progression of renal damage was seen over 2-7 years. Regression analysis showed a strong association between Grades IV, V reflux and the presence of renal damage (P < 0.001). Review of the degrees of fetal renal pelvic dilatation showed that 60/69 infants were detected because of mild (4-9 mm) dilatation. The majority (43/60) had lower grades of reflux (Grades I, II, 3), but there was no obvious cut-off between 4 and 9 mm that could predict high grade VUR (Grades IV, V).

CONCLUSIONS: The use of 4 mm to define an abnormal fetal renal pelvis allows a much larger group of infants with high grade primary VUR to be detected than if a higher cut-off measurement is used. Although it also detects many more infants with low grade primary VUR, there is no obvious cut-off point at which this effect predominates. Progressive renal damage was not seen in follow up of up to 7 years of age. Renal damage on DMSA scanning in this group is almost exclusively a pattern of global contraction of function. The presence of high-grade VUR appears to be the only important factor in predicting the presence of renal damage.