Use of pelvic ultrasound in the diagnosis of megarectum in children with constipation

PurposeIt has not been possible so far to differentiate slow transit constipation from functional fecal retention because the existing medical literature lacks data on rectal dimensions for healthy children or children with chronic idiopathic constipation (CIC). We, for the first time, describe the use of pelvic ultrasound (US) to achieve this.MethodsA pelvic US was carried out on 82 children with a full or partially full bladder and with no history of bowel problems and on 95 children with CIC. The rectal crescent seen behind the bladder was measured. All children also had documentation of their age, weight, and height.ResultsThe median age, weight, and height for the healthy children were comparable with those of the children with CIC. The median rectal crescent size in children with constipation was 3.4 cm (range, 2.10-7.0; IQR, 1.0), as compared with 2.4 cm (range, 1.3-4.2; IQR, 0.72) in the healthy children, and this difference is statistically significant on multiple regressions of log for rectal diameter, adjusted for height, weight, and age (P value< .001).ConclusionPelvic US is a quick child-friendly investigation, which can be used to document the presence of megarectum. It should be the first line investigation for all the children with CIC.