The purpose of a recent study published in Pediatrics International was to assess the usefulness of rectal diameter measurement on ultrasonography as a diagnostic tool for fecal retention in children. This study enrolled 80 children with functional constipation and 20 without constipation. All patients underwent physical examination, including digital rectal examination. In addition, 45 children underwent ultrasonography in three differential planes - transection above the symphysis, under the ischial spine, and at the bladder neck. The results disclosed that rectal diameter was wider at all measuring points in children with fecal retention relative to those without fecal retention. While children with constipation and fecal retention had a wider rectal diameter above the symphysis than those without. The cut-off for the rectal diameter above the symphysis, measured to identify fecal retention, was 27 mm with high sensitivity and specificity. Therefore, it was confirmed that ultrasound rectal diameter measurement can be used to detect fecal retention in children.