Conditions that mimic Hirschsprung's disease, but that are not Hirschsprung's disease.

Hirschsprung's disease (HSCR) is widely recognized in pediatric surgery. This condition has been elucidated, and therapeutic approaches have been developed. However, even when ganglion cells are present in the rectum, some patients still experience symptoms such as bowel obstruction, intestinal dilatation, and chronic constipation, which are similar to those observed in HSCR. A consensus regarding the terminology for these diseases is yet to be established. This group of diseases was defined as 'allied disorders of Hirschsprung's disease' (ADHD). They are classified into two categories based on pathology: (1) Abnormal ganglia, including immaturity of ganglia, hypoganglionosis, and intestinal neuronal dysplasia; and (2) Normal ganglia, including megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS), segmental dilatation, internal anal sphincter achalasia, and chronic idiopathic intestinal pseudo-obstruction (CIIP). Hypoganglionosis, MMIHS, and CIIP are particularly severe and not curable by surgery. Guidelines were compiled to facilitate an accurate clinical diagnosis and provide appropriate treatment strategies for each disease. A full-thickness rectal biopsy with H&E and acetylcholinesterase staining is often required for a differential diagnosis. Patients are now able to survive longer with enteral nutrition combined with long-term intravenous nutrition and decompression of the gastrointestinal tract. However, all treatment strategies are symptomatic. It is necessary to improve the results of small intestine transplantation and to develop new therapies using regenerative medicine.