Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

Section VI: Backcountry Medicine 205

The muscular wall of the abdomen lies outside the peritoneum, and therefore it is not within the abdominal cavity. These skeletal muscles provide protection and support for the abdominal con- tents. They contract in response to both the com- mands associated with voluntary movement and the involuntary need for abdominal protection. The muscles themselves can also be a source of pain that can be difficult to distinguish from intra- abdominal problems. Assessment of Abdominal Pain Your assessment of abdominal pain will go much better with a basic understanding of the struc- ture, function, and nerve supply of the abdominal organs. The nerve cells in hollow organs transmit pain sensations primarily when stretched, like when your stomach is distended by a big meal. Stretching a hollow organ stimulates muscular contraction, causing the pain of distention to become worse temporarily. We usually call this a cramp. It is also useful to note that the pain of a dis- tended hollow organ tends to be poorly localized at the general level of innervation, rather than identified as a specific spot. Because peristalsis increases the pain in waves, the discomfort tends to be intermittent. The mechanism is usually gas, fluid, and spasm created by a viral illness, food intolerance, or constipation. This type of pain is less likely to be serious. The patient with not serious abdominal painmay tighten the abdominal wall muscles in response to the pressure of your abdominal palpation but can voluntarily relax themwhen encouraged to do so. This is known as voluntary guarding. Tenderness elicited on examination tends to be nonspecific and relatively mild. Bowel sounds are usually normal to hyperactive. This kind of abdominal pain is usually associated with conditions that are well contained within the gut, not affecting the abdominal cavity itself. If the condition progresses to a more serious problem, you may begin to see the signs and

symptoms of peritoneal irritation inside the abdominal cavity. Unlike the hollow organs, the peritoneum is specifically innervated like your skin surface. An inflamed peritoneum causes pain localized to the site of irritation and aggravated by movement as the inflamed membranes rub against each other. The pain tends to be more constant than crampy. Bowel sounds may be reduced or absent. Hollow Organ Problems In a textbook case of appendicitis, for example, the problem usually begins with obstruction. The appendix is a hollow organ connected to the large intestine in the lower-right quadrant of the abdo- men. Obstruction of the appendix ultimately leads to infection and swelling. The early symptoms are often the generalized, cramp like discomfort typi- cal of intestinal distention. Because the appendix and first few centimeters of the large intestine are innervated with the small intestine, the pain is felt around the umbilicus. It would be impossible to distinguish this from mild gas pains, and you would not label it as serious. General Principles

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The hollow organs including the stomach, intestines, appendix, and gall bladder are prone to obstruc- tion, infection, and rupture due to trauma. As the infection progresses, the swollen and inflamed appendix begins to irritate the perito- neal lining of the intestine and abdominal cavity. The symptoms begin to change from generalized periumbilical cramping to localized constant pain in the lower-right quadrant. Abdominal wall