BACKGROUND: Patients with Hirschsprung disease lack the normal rectoanal inhibitory reflex, which can be studied with anorectal manometry or US. OBJECTIVE: To see whether the rectoanal inhibitory reflex could be visualised with a modified contrast enema, thereby increasing the diagnostic accuracy of the contrast enema and reducing the number of rectal biopsies. MATERIALS AND METHODS: Fifty-nine boys and 42 girls (median age, 12 months) with suspected Hirschsprung disease were examined with a modified contrast enema, supplemented with two injections of cold, water-soluble contrast medium, to induce the reflex. Two paediatric radiologists evaluated the anonymised examinations in consensus. The contrast enema findings were correlated with the results of rectal biopsy or clinical follow-up. RESULTS: Five boys and one girl (median age, 7.5 days) were diagnosed with Hirschsprung disease. The negative predictive value of the rectoanal inhibitory reflex was 100%. A contrast enema with signs of Hirschsprung disease in combination with an absent rectoanal inhibitory reflex had the specificity of 98% and sensitivity of 100% for Hirschsprung disease. CONCLUSION: The modified contrast enema improves the radiological diagnosis of Hirschsprung disease. By demonstrating the rectoanal inhibitory reflex in children without Hirschsprung disease, we can reduce the proportion of unnecessary rectal biopsies.
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