1. since in Hirschsprung's disease [HD] there are no ganglion
nerve bodies in the colon thus it cannot move out stool from colon to anus resulting in chronic constipation
and intestinal obstruction
[causing proximal section of bowel to become distended with feces, sometimes called as congenital aganglionic megacolon]
2. since it is from childhood, thus hopefully doctors would have gone through baseline investigations like barium X-ray, manometry, biopsy
to diagnose the problem, and if presently the problem is interfering with your day to day living you can ask for treatment options like Ostomy Surgery or pull-through procedure.
3. because of TPN (Total Parenteral Nutrition
) which has to be cycled intravenously, because of the risk of dehydration
and lack of weight gain due to the high losses of stomal output from their ostomies , [ probable reason of death of your brother], there is a very restricted diet [consult with a Dietitian regarding the same]
4. other major concern will be high growth of bacteria due to building up of feces, which may cause serious infections [enterocolitis] if the problem is not treated.
5. since there is associated intestinal obstruction which causes constipation which leads to vomiting
and thereby loss of weight [ which can be a reason of not gaining weight]
6. since there is loss of appetite in people suffering with HD, while you are feeling constantly hungry, this means you have to be evaluated by a Gastroenterologist for any other morbid pathology.
7. Hirschsprung disease appears to have a dominant pattern of inheritance, which means one copy of the altered gene in each cell may be sufficient to cause the disorder. The inheritance is considered to have incomplete penetrance because not everyone who inherits the altered gene from a parent develops Hirschsprung disease. [reason of your last query].