Impact of micturating cystourethrography and DMSA renal scintigraphy on the investigation scheme in children with urinary tract infection.

OBJECTIVE: The relationships among urinary tract infection (UTI), vesicoureteral reflux (VUR), and permanent renal damage in children are not fully understood. The aim of this study was to evaluate the incidence of renal scarring in children with a history of UTI and to determine the change in the probability of permanent renal damage owing to the presence of VUR documented on micturating cystourethrography (MCU).

METHODS: We analyzed 201 children (400 renal units, two children with solitary kidney). Seventy-four boys and 127 girls (aged 7 months to 7 years, median 2.5 years) with culture verified UTI were referred for technetium-labeled dimercaptosuccinic (DMSA) renal scintigraphy 4-6 months after acute UTI. MCU was also performed mostly 1 month prior to DMSA. Statistical analysis was performed using chi2 test or Fisher's exact test. Likelihood ratio (LR) positive and negative, diagnostic odds ratio (DOR), and post-test probability of (no) disease were calculated for VUR on MCU versus scarring on DMSA.

RESULTS: Vesicoureteral reflux was found in 158 (39.5%) kidneys, and evaluated as grades I, II, III, IV, and V in 3, 70, 43, 25, and 17 refluxing renal units (RRU), respectively. Permanent renal damage according to DMSA was seen in 15.2% (61/400) kidneys. Scarring was shown in 29.7% (47/158) of kidneys with VUR and in 5.8% (14/242) kidneys without VUR (P<0.0001). LR positive was 2.353 (95% CI 1.889, 2.865), LR negative 0.341 (95% CI 0.209, 0.523), and DOR 6.895 (95% CI 3.533, 14.093). Rate of scarring significantly increased with VUR of grades III, IV, and V. There was no significant difference in the incidence of scarring in kidneys without VUR and RRU with low-grade (I and II) VUR (P=0.306). The presence of VUR on MCU increased the chance of renal damage on DMSA by about 15%, whereas negative MCU increased the chance of no-renal involvement by 9%.

CONCLUSIONS: Micturating cystourethrography should not be used as a first-line test to rule out the permanent renal damage owing to UTI. The priority of imaging strategy should be focused on early identification of renal lesions to prevent further deterioration.