AIM: To study whether diurnal variations and time in relation to defecation has to be taken into account when measurements of rectal diameter are used to determine faecal impaction in constipated children.
METHODS: Repeated ultrasound measures of rectal diameter were performed in 28 children (14 constipated/14 healthy, aged between 4 and 12 years) every third hour during 24 h. After defecation, three additional scans were performed at 1-h intervals.
RESULTS: No diurnal variation in rectal diameter was found in the healthy group. In the constipated group, mean rectal diameter was significantly larger at 2 pm (P = 0.038) and 5 pm (P = 0.006). There were significant differences between rectal diameter in the healthy group and the constipated group at 2 pm (P = 0.016) and 5 pm (P = 0.027). When we omitted the rectal diameter of five constipated children who had their first bowel movement after 5 pm, there were no difference between groups (2 pm (P = 0.103)/5 pm (P = 0.644) ). Only in the constipated group, rectal diameter exceeded 3 cm without the patients feeling the urge to defecate.
CONCLUSION: We found no independent daily variation in either group without relation to defecation. There was a relation between defecation and changes in rectal diameter in both healthy children and constipated children during maintenance treatment.Asking for defecation signals before scanning should be considered a routine question, and a positive answer should cause postponement of the scan.