The diameter of the rectum on ultrasonography as a diagnostic tool for constipation in children with dysfunctional voiding

Purpose: We proved the accuracy of the transverse diameter of the rectum on ultrasonography as an additional parameter for diagnosing constipation in children with lower urinary tract dysfunction. Materials and Methods: The diameter of the rectum on bladder ultrasonography in a constipated group of patients with dysfunctional voiding was compared to this diameter in a control group of patients with a normal defecation pattern. A total of 49 children were included. Group 1 consisted of 23 patients with a positive history of dysfunctional voiding and, according to pediatric gastroenterological practice, constipation. Control group 2 consisted of 26 patients without lower urinary tract dysfunction and a normal defecation pattern. In each group a defecation questionnaire was administered and physical examination of the abdomen was done. In all patients a 7.5 MHz probe was used to measure the transverse diameter of the rectum behind the bladder on ultrasonography. The probe was applied on the abdominal skin approximately 2 cm above the symphysis. Measurement was performed with a filled bladder at an angle of about 15 degrees downward from the transverse plane. Results: In constipated group 1 the mean diameter of the rectum was 4.9 cm (95% CI 4.4 to 5.3). In the control group the mean diameter of the rectum was 2.1 cm (95% CI 1.8 to 2.4). In group 1 the diameter of the rectum was significantly larger than in group 2 (p <0.001). None of the patients had a sensation to defecate during the investigation. There was no significant difference in age between the 2 groups (p = 0.20) and no significant difference between them in the period between the last time that stool was passed prior to the time of rectal measurement (p = 0.16). Conclusions: The transverse diameter of the rectum measured by lower abdominal ultrasound provides an additional accurate parameter with which to diagnose constipation in patients with nonneurogenic bladder-sphincter dyssynergia.