Introduction: Plain kidney ureter bladder radiography (KUB) is widely used for the evaluation of constipation in children with bladder and bowel dysfunction (BBD); however, there is varying evidence to support its routine diagnostic use. One drawback to KUB is radiation exposure. The dangers of radiation in children are well-documented and As Low As Reasonably Achievable states to avoid non-beneficial radiation. This risk is especially high in children who undergo repeated imaging in the follow up of constipation treatment. We sought to assess the effectiveness of KUB to diagnose children with BBD by comparing it to four diagnostic tests: the Dysfunctional Voiding Symptom Score (DVSS), Rome IV criteria, rectal diameter on ultrasound (RD), and the Bristol Stool Score. Methods: We prospectively enrolled a cohort of patients presenting to an academic pediatric urology practice with symptoms of BBD. Severity of stool burden on KUB (mild, moderate, or severe), RD on ultrasound (= 3.4 cm), DVSS, Rome IV, and Bristol Stool Score were obtained for each patient. All imaging was interpreted by a pediatric radiologist and urologist. Primary outcomes were the association between the four diagnostic tests and KUB stool burden. Secondary measure were age, sex, BMI, treatment, and outcomes. Pearson’s rho bivariate analysis of all individual variables versus KUB was performed, as well as multivariate regressions to determine if multiple measures were predictive of KUB stool burden when combined. Results: Between October 2020 and May 2022, 50 patients were enrolled. All children were under the age of 18, with a mean age of 7.5 +/- 2.2 years, and 38% were male. Average BMI was 19.16 +/- 5.34. When comparing individual variables to KUB in bivariate analyses, it was found that RD on ultrasound is predictive of significant stool burden on KUB (p=0.03). No other individual variables were predictive. In the multivariate analyses, no combination of tests was found to be predictive of KUB. Increased RD on ultrasound was not predictive of treatment response. Conclusions: We compared the effectiveness of four commonly used diagnostic tests in children with BBD to validate the use of KUB. We found insufficient evidence to support a diagnostic association between clinical symptoms (DVSS and Rome IV) and fecal load on KUB. Our results support the use of RD on ultrasound as a non-radiating alternative to KUB to determine stool burden. RD has been proposed to provide an objective measure for diagnosis and monitoring of treatment response; however, unlike prior studies, we did not find initial increased RD to be predictive of treatment response. SOURCE OF Funding: None
