Rosh Pediatrics Practice Exam

What is the gold standard test for diagnosing Hirschsprung disease?

1. Contrast enema

2. Radiopaque marker study

3. Rectal biopsy

4. Sweat chloride test

The correct answer is: Rectal biopsy

The gold standard test for diagnosing Hirschsprung disease is the rectal biopsy. This procedure allows for direct histological examination of the rectal tissue, specifically to check for the presence of ganglion cells. In Hirschsprung disease, there is an absence of these ganglion cells in the affected segment of the bowel, leading to an inability to relax the rectum and the distal colon, which results in a functional obstruction. While other tests may provide supportive information, such as a contrast enema showing a dilated colon and a narrowed rectum, these methods cannot definitively confirm the diagnosis. Similarly, a radiopaque marker study can be used to evaluate bowel function but does not provide pathological confirmation of the disease. The sweat chloride test is unrelated to Hirschsprung disease and is typically used to diagnose cystic fibrosis. Therefore, a rectal biopsy remains the definitive diagnostic test for Hirschsprung disease due to its specificity and ability to confirm the absence of ganglia in the rectal wall.