Constipation: This is a common issue in children, often presenting with abdominal pain, and can be related to dietary habits, fluid intake, or bowel habits.
Viral Gastroenteritis: Also known as the stomach flu, it's a frequent cause of abdominal pain in children, usually accompanied by diarrhea, vomiting, and sometimes fever.

Appendicitis: Although more common in teenagers, it can occur in younger children, presenting with abdominal pain that often starts around the navel and then moves to the lower right abdomen.
Urinary Tract Infection (UTI): Can cause abdominal pain, especially if the infection involves the kidneys (pyelonephritis), and is often accompanied by symptoms like dysuria or frequent urination.
Functional Abdominal Pain: Part of functional gastrointestinal disorders, this can include irritable bowel syndrome (IBS), functional dyspepsia, or abdominal migraine, which are common in children and can be related to stress, eating habits, or other factors.

Intussusception: A condition where a part of the intestine slides into an adjacent part, potentially cutting off blood flow. It's an emergency and can present with severe abdominal pain, vomiting, and sometimes bloody stools.
Pneumonia: Lower lobe pneumonia can cause referred abdominal pain, especially if the diaphragm is irritated.
Diabetic Ketoacidosis (DKA): Can present with abdominal pain, nausea, vomiting, and is a medical emergency requiring prompt treatment.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic abdominal pain, diarrhea, weight loss, and other symptoms.

Hernias: Though not extremely rare, they are less common causes of abdominal pain in children and can sometimes cause intestinal obstruction if they become incarcerated.
Pancreatitis: Inflammation of the pancreas, which can be caused by various factors including gallstones, certain medications, or genetic conditions.
Malrotation with Volvulus: A condition where the intestine twists around itself, cutting off its blood supply. It's a surgical emergency.
Neuroblastoma: A type of cancer that can cause abdominal pain if the tumor is located in the abdomen, though it's much rarer than other causes of abdominal pain in children.