Constipation: This is a common issue in children with Down syndrome due to decreased bowel motility, dietary factors, and potential hypothyroidism, which can also be more prevalent in this population.

Gastroesophageal Reflux Disease (GERD): Children with Down syndrome are at an increased risk for GERD due to anatomical and physiological differences, which can lead to bloating and discomfort.
Lactose Intolerance or Other Dietary Intolerances: These conditions can cause bloating, gas, and abdominal discomfort, and may be more noticeable in children with Down syndrome due to potential difficulties in communicating discomfort.
Gastrointestinal Infections: Such as giardiasis, which can cause bloating, gas, and abdominal pain, and might be considered given the child's age and potential for exposure.

Intussusception: Although less common, intussusception is a serious condition that requires immediate attention. It can present with intermittent abdominal pain, vomiting, and bloating, and is a critical diagnosis not to miss.
Appendicitis: While the classic presentation of appendicitis includes pain, fever, and vomiting, children with Down syndrome might have atypical presentations, making it crucial to consider this diagnosis.
Obstruction: Either due to adhesions, volvulus, or other causes, obstruction can lead to severe abdominal pain, vomiting, and bloating, and requires prompt surgical intervention.

Celiac Disease: An autoimmune reaction to gluten, which can cause abdominal bloating, diarrhea, and failure to thrive. It's less common but should be considered, especially if there's a family history or if the child has other autoimmune conditions.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic abdominal pain, bloating, diarrhea, and weight loss. They are less common in young children but should be considered if other diagnoses are ruled out.