Appendicitis: This condition is a common cause of abdominal pain, especially around the umbilical region, which can later localize to the right lower quadrant. Fever and vomiting are also typical symptoms, making appendicitis a leading consideration.

Gastroenteritis: Inflammation of the stomach and intestines can cause fever, vomiting, and abdominal pain. The pain is often diffuse and can be around the umbilical area.
Mesenteric Lymphadenitis: This condition involves inflammation of the lymph nodes in the mesentery and can mimic appendicitis, presenting with fever, vomiting, and abdominal pain.
Intestinal Obstruction: Obstruction of the intestine can cause severe abdominal pain, vomiting, and fever. The pain can be diffuse or localized around the umbilical region.

Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause severe abdominal pain, vomiting, and fever. It's crucial to diagnose early to prevent complications.
Ectopic Pregnancy: Although less common in this presentation, an ectopic pregnancy can cause abdominal pain, vomiting, and fever if there is associated bleeding or rupture.
Perforated Visculitis or Ulcer: Perforation of a viscus (such as the intestine) can lead to peritonitis, presenting with severe abdominal pain, fever, and vomiting.

Meckel's Diverticulitis: Inflammation of a Meckel's diverticulum, a congenital anomaly of the small intestine, can cause abdominal pain, fever, and vomiting.
Ovarian Torsion: Twisting of an ovary can cause severe abdominal pain, vomiting, and sometimes fever. It's more common in females and requires urgent attention.
Hernias: Incarcerated or strangulated hernias can cause severe abdominal pain, vomiting, and fever, especially if they involve the intestine.