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More adult patients visit EDs annually in the U.S. for “stomach and abdominal pain, cramps, or spasms” than for any other chief complaint. In 2006, 6.7% of ED visits—8.04 million patient encounters—were for abdominal pain.1 Demographics (age, gender, ethnicity, family history, sexual orientation, cultural practices, geography) influence both the incidence and the clinical expression of abdominal disease. The history, vital signs, and physical findings may not point to a specific diagnosis, and laboratory testing is often not helpful. Although we cannot always identify the exact cause of the patient’s pain, we do seek to exclude life-threatening disease and to narrow the list of diagnostic possibilities for further workup. On the whole, clinical suspicion for serious disease is paramount, especially for patients in high-risk groups.

Traditionally, abdominal pain has been divided into three neuroanatomic categories: visceral, parietal, and referred.

Visceral Pain

Visceral pain is usually caused by the stretching of unmyelinated fibers that innervate the walls or capsules of organs. Less commonly, it is caused by early ischemia or inflammation. Visceral pain is often described as “crampy, dull, or achy,” and it can be either steady or intermittent in nature. Patients with colicky visceral pain are often unable to lie still. Because the visceral afferents follow a segmental distribution, visceral pain is localized by the sensory cortex to an approximate spinal cord level determined by the embryologic origin of the organ involved (Table 74-1).

Table 74-1 Visceral Pain Features

Because intraperitoneal organs are bilaterally innervated, stimuli are sent to both sides of the spinal cord, causing intraperitoneal visceral pain to be felt in the midline, independent of its right- or left-sided anatomic origin. For example, stimuli from visceral fibers in the wall of the appendix enter the spinal cord at about T10. When obstruction causes appendiceal distention in early appendicitis, pain is initially perceived in the midline periumbilical area, corresponding roughly to the location of the T10 cutaneous dermatome.

Parietal Pain

Parietal (somatic) abdominal pain is caused by irritation of myelinated fibers that innervate the parietal peritoneum, usually the portion covering the anterior abdominal wall. Because parietal afferent signals are sent from a specific area of peritoneum, parietal pain—in contrast to visceral pain—can be localized to the dermatome superficial to the site of the painful stimulus. As the underlying disease process evolves, the symptoms of visceral pain give way to the signs of parietal pain, causing tenderness and guarding. As localized ...

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