Explanation:
All of the above should be included in the differential diagnosis.

Bowel obstructions are a frequently encountered surgical problem leading to abdominal pain, nausea, vomiting, diarrhea or constipation among other symptoms. Constipation, which may mimic a bowel obstruction, is another common cause of abdominal pain.

Appendicitis is the most common cause of an acute surgical abdomen in children and adolescents; abdominal pain, fever, nausea and vomiting are classic symptoms.

In right lower lobe pneumonia, pain may be referred to the right side of the abdomen.

The patient may be sexually active, therefore Pelvic Inflammatory Disease and ectopic pregnancy should be included in the differential. Ovarian cysts can develop in females of any age. Ovarian torsion, most commonly occurring in the female early reproductive years, is also a possibility although rare.

Acute pancreatitis produces abdominal pain, initially mild or severe, that may radiate to the back. Nausea, vomiting and fever may also be present.

Cholycystitis is inflammation of the gall-bladder, most commonly caused by an obstruction of the cystic duct. Patients present with abdominal pain (frequently epigastric and followed by right upper quadrant), usually nausea and vomiting, and sometimes fever.

Mesenteric adenitis is inflammation of the mesenteric lymph nodes, in the right lower abdominal quadrant, caused by an infectious process. As patients present with abdominal pain (often in the right lower quadrant), fever, nausea, and sometimes diarrhea, mesenteric adenitis is often confused with appendicitis.

Gastroenteritis or a urinary tract infection should also be considered.

Also note that pneumonia is a possibility in a child presenting with abdominal pain, but not as likely in an older child. A 14-year-old should have symptoms of a pneumonia (at least a cough).