Abdominal pain falls into three categories:
- Visceral (splanchnic) pain,
- Parietal (somatic) pain,
- referred pain.
Visceral Pain
- Visceral pain occurs when noxious stimuli affect a viscus, such as the stomach or intestines.
- Tension, stretching, and ischemia stimulate visceral pain fibers. Tissue congestion and inflammation tend to sensitize nerve endings and lower the threshold for stimuli.
- Because visceral pain fibers are bilateral and unmyelinated and enter the spinal cord at multiple levels,visceral pain usually is dull, poorly localized, and felt in the midline.
Localisation of Visceral Pain
- Pain from foregut structures (e.g., the lower esophagus and stomach) generally is felt in the epigastrium.
- Midgut structures (e.g., the small intestine) cause periumbilical pain,
- and hindgut structures (e.g., the large intestine) cause lower abdominal pain.
Parietal Pain
- Parietal pain arises from noxious stimulation of the parietal peritoneum.
- Pain resulting from ischemia, inflammation, or stretching of the parietal peritoneum is transmitted through myelinated afferent fibers to specific dorsal root ganglia on the same side and at the same dermatomal level as the origin of the pain.
- Parietal pain usually is sharp, intense, discrete, and localized, and coughing or movement can aggravate it
Referred Pain
- Referred pain is felt in remote areas supplied by the same dermatome as the diseased organ. It results from shared central pathways for afferent neurons from different sites