What is the most common cause of bowel obstruction in children aged 6 months to 3 years?

Intussusception is the most common cause of bowel obstruction in children aged 6 months to 3 years. This condition occurs when a part of the intestine telescopes into an adjacent segment, leading to blockage. In this age group, the most common site for intussusception is typically the ileocecal junction.

The prevalence of intussusception in young children can be attributed to factors such as increased intestinal motility and lymphoid tissue hypertrophy, which is often seen in response to viral infections. As a result, it tends to manifest acutely with symptoms like abdominal pain, vomiting, and sometimes the presence of currant jelly stools, which are indicative of blood and mucus in the stool caused by the obstruction.

Understanding the common presentation and age group at risk can enhance recognition and timely diagnosis, which is critical given the potential for complications such as ischemia and perforation of the intestine if not treated expeditiously. The other conditions listed, while they can cause obstruction, either occur less frequently in this age range or are associated with different underlying mechanisms.