In inflammatory pain involving the peritoneum, which is harder to localize?

• A. Visceral peritoneum
• B. Parietal peritoneum
• C. Skin
• D. Bone

Answer: (A)

Pain localization depends on the wiring of the tissue’s nerves. The visceral peritoneum is supplied by autonomic (visceral) sensory fibers that travel with sympathetic nerves to the spinal cord. These signals converge with somatic fibers at the same spinal levels, so the brain has difficulty pinpointing the exact source, producing a dull, diffuse, poorly localized pain often with referred sensations. In contrast, the parietal peritoneum is innervated by somatic nerves from the abdominal wall, giving sharp, well-localized pain with precise location and tenderness. Skin and bone are also somatically innervated and tend to produce localized pain rather than diffuse visceral pain. Thus, inflammatory pain involving the visceral peritoneum is the hardest to localize.