Simply put, abdominalgia is the pathological changes to organs inside and outside the abdomen for various reasons, which presents ache in abdominal region, acute or chronic. It is a kind of complicated disease and could be caused by many different factors.

The common pathogenesis in western medicine is as follows:
(1). Gastroduodenal ulcer, Crohn's Disease, Viral gastroenteritis, Lactose intolerance, Gastric Cancer, and Gastroesophageal Reflux;
(2). Small bowel and colons diseases like Appendicitis, Irritable Bowel Syndrome (IBS), Intestinal Obstruction, enteritis, diarrhea, intestinal parasitic diseases;
(3). Acute or chronic hepatitis and liver cancer;
(4). Disease in biliary tract and pancreas, such as Cholecystitis, gallstone, pancreatitis, and carcinoma head pancreas;
(5). Peritonitis ensued frequently from perforation of gastrointestinal tract and rupture of spleen;
(6). Visceral organs in chest, like lobar pneumonia in early stage and acute inferior diaphragmatic infarction, is usually misdiagnosed as lesion in celiac organs;
(7). Disorders in urogenital organs in women like renal and ureteral stone, ectopic pregnancy, salpingitis, ovarian cyst torsion, acute cystitis, urinary infection, and painful menstruation, etc.
(8). Systemic diseases like diabetes.

From the perspective of Traditional Chinese Medicine (TCM), it can be caused by following reasons:
(1). Coagulated cold syndrome;
(2). Heat accumulation;
(3). Yang deficiency syndrome;
(4). Food retention syndrome;
(5). Syndrome of Qi stagnation;
(6). Syndrome of blood stasis.