There are mainly 2 types of investigations
Barium Enema: This consists of filling the rectum with a contrast liquid - barium and looking at the large intestine. The abnormal segment will be thin and contracted, the normal segment will be dilated and is proximal to the abnormal segment.The accuracy of this method is about 75% only.
Full thickness Rectal Biopsy: Here, a small piece of the rectum is taken surgically and is sent for examination under the microscope to look for the Ganglion cells and nerve bundles. In cases with Hirschsprung disease, there will be no Ganglion cells and will have excess nerve bundles. This is almost 100% accurate. Once the diagnosis is confirmed, then the only answer is surgery. This may require staged surgeries , or may be done with a single stage surgery. This depends on the condition of the child, his/her state and size of the large intestine and other factors. If the exact length of the abnormal intestine is known and is excised, the results are usually uniformly good with minimal complications.