Abdominal pain is the most important and commonest alimentary symptom.
Mechanism of abdominal pain are the following
- Spasm or stretch of the smooth muscles of hollow viscus
 - Ischemia of viscera - Spleen, intestine etc.
 - Stretch of the capsule - Hepatic pain ,Stretch of Glisson's capsule
 - Pain from parietal peritoneum - Inflammation, malignancy, irritation etc.
 - Referred pain to abdomen
 - Psychogenic - Depression, somatisation disorder