diverticulitis
Excessive gas
Chronic constipation
Lactose intolerance (milk intolerance)
Viral gastroenteritis (stomach flu)
Irritable bowel syndrome (sensitive stomach with intermittent episodes of diarrhea and constipation)
Heartburn or indigestion
Gastroesophageal reflux
Ulcers
Cholecystitis (inflammation of the gallbladder) with or without gallstones
Appendicitis (inflammation of the appendix)
Diverticular disease, including inflammation of small pouches that form in the large intestines (diverticulitis)
Bowel obstruction -- in addition to pain, this causes nausea, bloating, vomiting, and inability to pass gas or stool
Food allergy
Food poisoning (salmonella, shigella)
Hernia
Kidney stones
Urinary tract infections
Pancreatitis (inflammation of the pancreas)
Intussusception (telescoping intestines) -- while uncommon, this is a serious possible cause of pain in an infant who may be drawing his or knees to the chest and crying to indicate the pain
Dissecting abdominal aortic aneurysm -- bleeding into the wall of the aorta
Parasite infections (Giardia)
Sickle cell crisis
Crohn's disease or ulcerative colitis
Ovarian cysts
Ovarian Cancer
Uterine fibroids
PID
Somatization disorder (psychological)
Hey Rid...did I miss any???
But most often, in the LLQ, it is only diverticulitis or irritable bowel