Approach to the patient with abdominal pain

Assessment and management of abdominal pain patients in the prehospital setting are difficult for a variety of reasons. The following objectives apply.

Anatomy and physiology considerations

The lungs, pleural cavity, and base of the heart are all in close proximity to the abdominal cavity and can be involved in conditions that can be perceived as abdominal pain. During development, the abdominal organs protrude into the peritoneal cavity and become enveloped with a layer of peritoneal lining, the visceral peritoneum. The outer surface of the peritoneal cavity is the parietal peritoneum. The peritoneal cavity allows for normal movement and sliding of the abdominal organs and provides a source of protection to the abdominal contents. The peritoneum provides a potential space for air, blood, or other fluids in pathological conditions. Some structures, such as the kidneys, ureters, pancreas, aorta, and portions of the duodenum, lie in the retroperitoneum. This area contains less sensory innervation, accounting for decreased pain perception and localization of pathological conditions involving these structures.

The etiologies of abdominal pain can be described as mechanical, inflammatory, or ischemic in nature. Mechanical etiologies include distension of a hollow organ (e.g. stomach, intestine, gallbladder, ureter) or stretching of the capsule of a solid organ (e.g. liver, spleen, kidney). Inflammatory causes include immune processes such as Crohn’s disease or ulcerative colitis and infection like appendicitis or diverticulitis. Ischemic pain may result from thrombotic or embolic disease of the vascular bed of abdominal organs or anatomic torsion (e.g. testicle or ovary).

The perception of these pathological states may cause different types of pain: visceral, somatic, or referred pain. Luminal or capsular distension will typically produce visceral pain by stimulation of nerves surrounding a hollow or solid organ. Because the innervation of organs is sparse and multisegmented, this pain is usually dull and poorly localized. When caused by an obstructive process, the pain is typically intermittent or colicky. Distension of a solid organ tends to produce more constant pain (e.g. hydronephrosis, hepatitis). Visceral pain is typically associated with other autonomic phenomena such as anorexia, nausea, and vomiting.

Somatic abdominal pain typically results from irritation of the parietal peritoneum from infection or inflammation. The pathological process stimulates peripheral nerves and the pain tends to be more intense and distinct than visceral pain. The evolution of acute appendicitis demonstrates both visceral and somatic pain. Early obstruction and distension of the appendix generate dull, poorly localized pain around the umbilicus. As inflammation progresses, the parietal peritoneum becomes involved and the pain becomes localized to the right lower quadrant.

The patient’s general appearance should be assessed. Seasoned EMS providers develop an immediate impression of those who are “sick.” A patient who limits his or her movement due to abdominal pain may have peritonitis as opposed to one who cannot find a position of comfort (e.g. kidney stones or aneurysmal pain).

The focus of the physical examination should be to identify potentially life-threatening conditions. Assessment and monitoring of vital signs are crucial. Indications of shock, including hypotension, tachycardia, narrow pulse pressure, and tachypnea, should be recognized. A hypotensive patient should be presumed to have a serious medical condition requiring immediate intervention. The patient’s temperature should also be evaluated, recalling that both fever and hypothermia may indicate significant disease such as sepsis.