Background: Childhood urinary tract infection (UTI) with or without vesicoureteric reflux (VUR) may predispose to renal scarring. There is no clear consensus in the literature regarding imaging following UTI in infancy. Aims: To define the role of cystography following a first UTI in children aged under 1 year, when urinary tract ultrasonography (US) is normal. Methods: Retrospective data collection of 108 children (216 renal units) aged under 1 year at the time of a bacteriologically proven UTI. All had a normal US and underwent both catheter cystogram and DMSA test. Sensitivity, specificity, likelihood ratios positive and negative, and diagnostic odds ratio were calculated for VUR on cystography versus scarring on DMSA.Results: VUR was shown in 25 (11.6%) renal units. Scarring on DMSA was seen in 8 (3.7 %) kidneys. Only 16% of kidneys with VUR had associated scarring; 50% of scarred kidneys were not associated with VUR. The likelihood ratio positive was 4.95 (95% CI 2.22 to 11.05) and the likelihood ratio negative was 0.56 (95% CI 0.28 to 1.11). The diagnostic odds ratio was 8.9, suggesting that cystography provided little additional information. Conclusion: Since only 16% of children with VUR had an abnormal kidney, the presence of VUR does not identify a susceptible population with an abnormal kidney on DMSA. In the context of a normal ultrasound examination, cystography contributes little to the management of children under the age of 1 year with a UTI. In this context, a normal DMSA study reinforces the redundancy of cystography.
Dimercaptosuccinic acid (DMSA) renal scan is presently the technique of choice for assessing renal scars. Recent advances suggest that ultrasonography could replace DMSA scan for this purpose. This paper describes the experience of a tertiary pediatric referral hospital performing ultrasonography and DMSA scans in the assessment of renal scarring. Investigations were conducted 3-6 months after patients presented with urinary tract infection (UTI). Results were extracted from the radiology information system and recorded for analysis. All children with a UTI who had undergone DMSA and ultrasound examination on the same day between January 1995 and December 1999 were included; 930 kidneys were compared. DMSA scan was utilized as the reference method. When used to detect focal renal scarring, ultrasonography had a sensitivity of 5.2%, specificity of 98.3%, a positive predictive value (PPV) of 50% and a negative predictive value (NPV) of 75.8%. When used to detect diffuse renal scarring, ultrasonography had a sensitivity of 47.2%, specificity of 91.8%, PPV of 60.8% and NPV of 86.6%. Our results demonstrate that although ultrasonography has a good specificity for the detection of renal scarring compared with DMSA, it has low sensitivity, PPV and NPV. Ultrasonography cannot be substituted for DMSA scan in the evaluation of focal renal scarring.
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