Abdominal Pain-Visceral Abdominal Pain-Somatic Abdominal Pain-Referred Abdominal Pain-Lumbar Sympathectomy-

Abdominal Pain

We will talk about Abdominal pain because it is one of the most important problems facing the physician. This section provides an anatomic basis for the different forms of abdominal pain found in clinical practice. Three distinct forms of pain exist:

 visceral, somatic, and referred pain.

Visceral Abdominal Pain

Visceral abdominal pain means pain in abdominal organs, visceral peritoneum, and the mesenteries. The sensations that arise in viscera reach the central nervous system in afferent nerves that accompany the sympathetic nerves and enter the spinal cord through the posterior roots.

Visceral pain from the stomach is commonly referred to the epigastrium The causes of visceral pain include impaired blood supply (ischemia) to a viscus, stretching of a viscus or mesentery, distention of a hollow viscus, and chemical damage  to a viscus or its covering peritoneum. Pain arising from an abdominal viscus is dull and poorly localized. Visceral pain is referred to the midline, probably because the viscera develop embryologically as midline structures and receive a bilateral nerve supply; many viscera later move laterally as development proceeds, taking their nerve supply with them.

violent contraction of smooth muscle cause Colic  is a form of visceral pain; it is commonly caused by luminal obstruction as in intestinal obstruction, in the passage of a gallstone in the biliary ducts, or in the passage of a stone in the ureters.

Many visceral afferent fibers that enter the spinal cord participate in reflex activity. Reflex sweating, salivation, nausea, vomiting, and increased heart rate may accompany visceral pain.

Somatic Abdominal Pain

Somatic abdominal pain in the abdominal wall can arise from the skin, fascia, muscles, and parietal peritoneum. It can be severe and precisely localized. When the origin is on one side of the midline, the pain is also lateralized. The somatic pain impulses from the abdomen reach the central nervous system in the following segmental spinal nerves:

■■ Central part of the diaphragm: Phrenic nerve (C3, 4, and 5)

■■ Peripheral part of the diaphragm: Intercostal nerves(T7 to 11)

■■ Anterior abdominal wall: Thoracic nerves (T7 to 12) and the1st lumbar nerve

■■ Pelvic wall: Obturator nerve (L2, 3, and 4)

The inflamed parietal peritoneum is extremely sensitive, and because the full thickness of the abdominal wall is innervated by the same nerves, it is not surprising to find cutaneous hypersensitivity (hyperesthesia) and tenderness. Local reflexes involving the same nerves bring about a protective phenomenon in which the abdominal muscles increase in tone. This increased tone or rigidity, sometimes called guarding, is an attempt to rest and localize the inflammatory process. Rebound tenderness occurs when the parietal peritoneum is inflamed. Any movement of that inflamed peritoneum, even when that movement is elicited by removing the examining hand from a site distant from the inflamed peritoneum, brings about tenderness.

Examples of acute, severe, localized pain originating in the parietal peritoneum are seen in the later stages of appendicitis. Cutaneous hyperesthesia, tenderness, and muscular spasm or rigidity occur in the lower right quadrant of the anterior abdominal wall. A perforated peptic ulcer, in which the parietal peritoneum is chemically irritated, produces the same symptoms and signs but involves the right upper and lower quadrants.

Referred Abdominal Pain

Referred abdominal pain is the feeling of pain at a location other than the site of origin of the stimulus but in an area supplied by the same or adjacent segments of the spinal cord. Both somatic and visceral structures can produce referred pain. In the case of referred somatic pain, the possible explanation is that the nerve fibers from the diseased structure and the area where the pain is felt ascend in the central nervous system along a common pathway, and the cerebral cortex is incapable of distinguishing between the sites. Examples of referred somatic pain follow. Pleurisy involving the lower part of the costal parietal pleura can give rise to referred pain in the abdomen because the lower parietal pleura receives its sensory innervation from the lower five intercostal nerves, which also innervate the skin and muscles of the anterior abdominal wall.

 

Lumbar Sympathectomy

Lumbar sympathectomy is performed mainly to produce a vasodilatation of the arteries of the lower limb in patients with vasospastic disorders. The preganglionic sympathetic fibers that supply the vessels of the lower limb leave the spinal cord from segments T11 to L2. They synapse in the lumbar and sacral ganglia of the sympathetic trunks. The postganglionic fibers join the lumbar and sacral nerves and are distributed to the vessels of the limb as branches of these nerves. Additional postganglionic fibers pass directly from the lumbar ganglia to the common and external iliac arteries, but they follow the latter artery only down as far as the inguinal ligament. In the male, a bilateral lumbar sympathectomy may be followed by loss of ejaculatory power, but erection is not impaired.