Final answer:
The gold standard for diagnosing Hirschsprung disease is a Rectal suction biopsy, where a lack of ganglion cells is a diagnostic feature. Therefore, the correct option is D.
Step-by-step explanation:
The gold standard for the diagnosis of Hirschsprung disease is d) Rectal suction biopsy. This procedure involves obtaining a tissue sample from the rectum, which is then examined microscopically for the absence of ganglion cells in the submucosal and myenteric plexuses.
This is a key diagnostic feature of Hirschsprung disease, where there is a lack of these nerve cells in parts of the bowel, leading to impaired movement of the bowels and severe constipation. Biopsy of the colon may also be used, but rectal suction biopsy is specifically useful for diagnosing Hirschsprung disease in the lower parts of the gastrointestinal tract.