Point-of-care ultrasound assessment of transrectal diameter to evaluate fecal load in children with anorectal malformations: adjunct imaging and utility in bowel management program

INTRODUCTION: Children with anorectal malformations (ARM) frequently experience impaired bowel function and require long-term bowel management. Assessment of fecal load commonly includes abdominal radiographs, which provide information on overall stool distribution but may require repeated imaging and are subject to interobserver variability. Ultrasound measurement of the transrectal diameter (TRD) has been proposed as a radiation-free adjunct in functional constipation, but evidence in children with ARM remains limited. This study aimed to evaluate point-of-care ultrasound (POCUS) measurement of TRD as an adjunct to clinical assessment for evaluating fecal load and monitoring bowel management in children with ARM. METHODS: In this prospective observational cohort study, children with ARM attending a tertiary colorectal clinic between April 2023 and January 2025 underwent standardized ultrasound assessment of TRD as part of a structured bowel management program. Findings were compared with children with functional constipation (FC) and healthy controls. TRD measurements were correlated with clinical symptoms of constipation and soiling. Receiver operating characteristic (ROC) analysis was performed. RESULTS: Fifty-seven children with ARM (mean age 5.7 years) were included, alongside 53 children with FC and 72 controls. Asymptomatic ARM patients demonstrated TRD values comparable to controls (2.20 vs. 2.05 cm, p = 0.246), whereas symptomatic ARM patients showed significantly increased TRD (3.64 cm, p < 0.001). ROC analysis identified a TRD cut-off of 3.1 cm with a sensitivity of 63.3% and specificity of 96.3%. During structured bowel management, TRD decreased below this threshold in parallel with clinical improvement. CONCLUSION: POCUS measurement of TRD is a feasible, radiation-free adjunct to clinical assessment in children with ARM. While it does not replace radiographic evaluation of global colonic stool burden, it may support monitoring within structured bowel management programs.