inal answer:
Cystic fibrosis and Hirschsprung's disease are direct causes of rectal prolapse in early childhood, while laxative abuse is unlikely in this age group.
Step-by-step explanation:
Rectal prolapse in children aged 6 months to 3 years can be attributed to several potential causes. However, among the options provided, Cystic fibrosis is recognized as a condition that might lead to rectal prolapse due to the thickening of intestinal secretions. This can make it difficult for a child to pass stools and ultimately result in the strain that can lead to rectal prolapse. Pinworm infection is another cause associated with rectal prolapse due to the irritation and eventual straining caused by the worms. Hirschsprung's disease can also result in rectal prolapse due to an abnormality that causes chronic constipation, leading to strain during bowel movements.
Laxative abuse is less likely to be the reason in this age group given the rarity of laxative use in very young children. While all options may have some validity, Cystic fibrosis and Hirschsprung's disease are more directly associated with rectal prolapse in early childhood.