Functional abdominal pain: This is the most common cause of abdominal pain in adolescents, often related to stress, anxiety, or irritable bowel syndrome. The pain is typically chronic or recurrent, diffuse, and not accompanied by other alarming symptoms.

Menstrual cramps (dysmenorrhea): Abdominal pain associated with menstruation, often accompanied by other symptoms like nausea, vomiting, and headache.
Constipation: A common issue in adolescents, leading to abdominal pain, bloating, and changes in bowel habits.
Gastroesophageal reflux disease (GERD): Stomach acid reflux can cause abdominal pain, especially after eating, and may be accompanied by heartburn and regurgitation.
Urinary tract infection (UTI): Bacterial infection of the urinary system, which can cause abdominal pain, dysuria, and frequent urination.

Appendicitis: Although less common, appendicitis is a surgical emergency that requires prompt diagnosis and treatment. Symptoms include severe abdominal pain, fever, and vomiting.
Ectopic pregnancy: A life-threatening condition where the embryo implants outside the uterus, causing abdominal pain, vaginal bleeding, and missed periods.
Ovarian torsion: A rare but serious condition where the ovary twists, cutting off its blood supply, and causing severe abdominal pain, nausea, and vomiting.
Inflammatory bowel disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic abdominal pain, diarrhea, weight loss, and fatigue.

Intussusception: A condition where a part of the intestine telescopes into another, causing abdominal pain, vomiting, and bloody stools.
Hernias: Abdominal wall defects that can cause pain, especially with coughing or straining.
Pancreatitis: Inflammation of the pancreas, which can cause severe abdominal pain, nausea, and vomiting.
Endometriosis: A condition where tissue similar to the uterine lining grows outside the uterus, causing chronic abdominal pain, heavy menstrual bleeding, and infertility.