Accuracy Of Subjective Vesicoureteral Reflux Timing Assessment- Supporting New VCUG Guidelines
Michelle A. Lightfoot, MD1, Derrick E. Ridley, BA2, Angela A. Arlen, MD3, Andrew J. Kirsch, MD1, Courtney M. McCracken, PhD4, Christopher S. Cooper, MD5, Michael Garcia-Roig, MD1.
1Emory University and Childrens Healthcare of Atlanta, Atlanta, GA, USA, 2Emory University School of Medicine, Atlanta, GA, USA, 3Yale University, New Haven, CT, USA, 4Emory University Department of Pediatrics - Biostatistics Core, Atlanta, GA, USA, 5University of Iowa Department of Urology, Iowa City, IA, USA.
Introduction: Bladder volume at time of vesicoureteral reflux(VUR) is an important prognostic indicator of spontaneous resolution and risk of pyelonephritis. VUR occurring at earlier filling volumes is associated with an increased likelihood of breakthrough febrile UTI and lower likelihood of spontaneous resolution. We aim to determine whether pediatric radiologists (PR) and pediatric urologists (PU) can accurately estimate the timing of reflux by examining VCUG images without prior knowledge of volume of contrast instilled.
Methods: Total bladder volume and volume at time of reflux were collected from children’s VCUG reports to determine volume at the onset of VUR. 39 patients were sorted into three groups: early/mid-filling reflux (VUR onset <75% bladder filling), late-filling (75-100%) and voiding only (during micturition). Images were shown to 3 PU and 2 PR in a blinded fashion. They were asked to estimate VUR timing based on the above categories. Weighted kappa score was calculated to assess rater agreement with the gold standard volume-based interpretation of VUR timing among physicians.
Results: Mean patient age at VCUG was 3.1±2.9 months, mean VUR grade 2.4±0.9, and 20 were female. Overall agreement among all five raters was moderate (k=0.43 (95% CI 0.36-0.50)). Individual agreement between rater and gold standard was fair with kappa values ranging from 0.13 to 0.43. Details of PU and PR agreement are outlined in the table. PU interpretation was less accurate than radiologist interpretation compared to the gold standard, however, both were fair at best. Interobserver variability was similar among PR and PU (k= 0.53 vs 0.50). PR and PU did not consistently identify any of the VUR timing groups.
Conclusion: Pediatric radiologists and urologists are unable to accurately and reliably characterize VUR timing on fluoroscopic VCUG. Accurate interpretation of VUR timing requires recording of the volume of contrast instilled at the time of reflux and maximum bladder capacity by the radiologist or radiology technician during VCUG. These findings support the recently published American Academy of Pediatrics protocol recommending the routine recording of bladder volume at the onset of VUR as a standard component of all VCUGs to more accurately assess risk of resolution and recurrent UTI.
| Overall Agreement Among Pediatric Urologists | |||
| Individual Agreement | Weighted Kappa | 95% CI | % Exact Agreement |
| Uro 1 vs. Uro 2 | 0.65 | (0.47 – 0.84) | 72.5% |
| Uro 1 vs. Uro 3 | 0.51 | (0.30 – 0.72) | 60.5% |
| Uro 2 vs. Uro 3 | 0.51 | (0.29 – 0.73) | 65.8% |
| Overall | 0.50 | (0.37 – 0.63) | 52.6% |
| Agreement with Pediatric Urologist and Volume-Based VUR Timing | |||
| Uro 1 | 0.36 | (0.12 – 0.60) | 55% |
| Uro 2 | 0.13 | (-0.10 – 0.36) | 37.5% |
| Uro 3 | 0.27 | (0.02 – 0.52) | 50% |
| Agreement Between Pediatric Radiologists | |||
| Rad 1 vs Rad 2 | 0.53 | (0.30 – 0.75) | 70% |
| Agreement with Pediatric Radiologist and Volume-Based VUR Timing | |||
| Rad 1 | 0.43 | (0.14 - 0.57) | 57.5% |
| Rad 2 | 0.32 | (0.09 – 0.54) | 47.5% |
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