[Role of anorectal manometry in the differential diagnosis of chronic constipation in children]

OBJECTIVES: 1. To evaluate the role of anorectal manometry in recognizing patients with histological abnormalities of the myenteric plexus as the cause of chronic constipation. 2. To correlate clinical features with the etiology of the constipation.METHODS: The etiology of the constipation was identified retrospectively from the medical records of 57 patients submitted to anorectal manometry. The test was performed in the Pediatric Gastroenterology Laboratory of the University Hospital of the State University of Campinas Medical School. The procedure was performed using a single-balloon system in which a water-perfused pressure transducer was interfaced with a polygraph and displayed on a computer screen. Manometry was performed in patients who, after 6 to 23 months of intense medical treatment using osmotic laxatives and dietary fibres (20 g/d), continued to develop fecal impaction and/or needed evacuatory enema. Regularization of bowel movements during at least 24 months follow-up or the visualization of abnormalities in myenteric plexus in rectal biopsy were used as reference points for the definitive diagnosis.RESULTS: Rectoanal reflex was present in 44 of the 57 patients (77%). Thirteen patients with a negative reflex underwent rectal biopsy which showed abnormalities of the ganglion cells in 10. Subsequent manometry performed on those three patients revealed a normal rectoanal reflex. Sensitivity, specificity, positive and negative predictive values of the manometric test were 1.0, 0.94, 0.77 and 1.0, respectively.CONCLUSIONS: Anorectal manometry is a diagnostic technique with very small possibility of error in differential diagnosis between constipation of a chronic functional nature and that which is secondary to ganglion cell abnormalities.