3: Abdominal Pain

CHIEF COMPLAINT

CONSTRUCTING A DIFFERENTIAL DIAGNOSIS

Abdominal pain is the most common cause for hospital admission in the United States. Diagnoses range from benign entities (eg, irritable bowel syndrome [IBS]) to life-threatening diseases (eg, ruptured abdominal aortic aneurysms [AAAs]). The first pivotal step in diagnosing abdominal pain is to identify the location of the pain. The differential diagnosis can then be limited to a subset of conditions that cause pain in that particular quadrant of the abdomen (Figure 3-1).

Several other pivotal points can help narrow the differential diagnosis including (1) the time course of the pain, (2) peritoneal findings on exam, (3) unexplained hypotension, and (4) abdominal distention. Each of these is reviewed below.

The time course of the pain is a pivotal feature. Some diseases present subacutely/chronically over weeks to months or years (eg, IBS) whereas others present acutely, within hours to days of onset (eg, appendicitis). In patients with their first episode of acute severe abdominal pain, a variety of life-threatening, must not miss diagnoses must be considered (eg, AAA). Many of these diseases that cause acute abdominal pain cannot recur because patients are either treated or die of complications (eg, AAA, acute appendicitis, splenic rupture.) Since prior episodes are incompatible with many of these diagnoses, a history of such prior episodes narrows the differential diagnosis. Therefore, the differential diagnosis of abdominal pain can be organized based on whether patients are presenting with their first episode of acute abdominal pain, a recurrent episode of acute abdominal pain, or chronic/subacute abdominal pain. Table 3-1 outlines the typical time course associated with different diseases causing abdominal pain. See Table 3-2 for a summary of abdominal pain organized by location, time course, and clinical clues.