Chapter 3-1: Approach to the Patient with Abdominal Pain - Case 1

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 (1) first episode of acute abdominal pain, (2) a recurrent episode of acute abdominal pain, or (3) 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.

Peritoneal findings of rebound tenderness, rigidity, and guarding are pivotal features and suggest an intra-abdominal catastrophe. Typical causes include AAA, bowel infarction (due to bowel obstruction or acute mesenteric ischemia), bowel perforation (due to appendicitis, peptic ulcer disease [PUD], diverticulitis), pancreatitis, or pelvic inflammatory disease (PID).

Unexplained hypotension is yet another potential pivotal clue. While many patients with abdominal pain experience hypotension due to dehydration from nausea, vomiting, or poor oral intake, some patients with abdominal pain present with unexplained hypotension. Unexplained hypotension can suggest sepsis, retroperitoneal hemorrhage, or other diseases. Table 3-3 lists diseases associated with abdominal pain and unexplained hypotension.

Orthostatic vital signs should be taken in patients with abdominal pain. They may provide invaluable diagnostic and therapeutic information.

The final pivotal finding is significant abdominal distention, which may develop from excess air or fluid in the abdomen. Excess air may occur with bowel obstruction or bowel perforation (free air). Excess fluid may be seen in patients with ascites or hemorrhage. Percussion and shifting dullness can usually distinguish excess air from fluid in such patients. Table 3-4 lists the diagnostic considerations in patients with abdominal distention.

Other important historical points include factors that make the pain better or worse (eg, eating), its’ quality, radiation of the pain, and associated symptoms (nausea, vomiting, anorexia, inability to pass stool and flatus, melena, hematochezia, change in color of the urine or stool, jaundice, fever, chills, weight loss, altered bowel habits, orthostatic symptoms, urinary symptoms) or prior abdominal surgeries (increasing the risk of small bowel obstruction [SBO]). Pulmonary symptoms or a cardiac history can be clues to pneumonia or myocardial infarction presenting as abdominal pain. In women, sexual and menstrual histories are important. The patient should be asked about alcohol consumption as well as prescription and over-the-counter medications and supplements.

A few final points about the physical exam are worth empha­sizing. First, vital signs are just that, vital. Hypotension, fever, tach­ypnea, and tachycardia are critical clinical clues that must not be overlooked. The HEENT exam should look for pallor or icterus. Jaundice suggests either hepatitis or biliary disease. Careful heart and lung exams can suggest pneumonia or other extra-abdominal causes of abdominal pain.

The physical exam of a patient with abdominal pain includes more than just the abdominal exam.

Of course, the abdominal exam is key. Inspection assesses for distention as noted above. Auscultation evaluates whether bowel sounds are present. Absent bowel sounds may suggest an intra-abdominal catastrophe; high-pitched tinkling sounds and rushes suggest an intestinal obstruction. Palpation should be performed last. It is useful to distract the patient by continuing to talk with him or her during abdominal palpation. This allows the examiner to get a better appreciation of the location and severity of maximal tenderness. The clinician should palpate the painful area last. The rectal exam should be performed, and the stool tested for occult blood. Finally, the pelvic exam should be performed in adult women and the testicular exam in men.

The patient’s history is not particularly suggestive of any diagnosis. The first pivotal point determines the location of the pain. Mr. C’s pain is in the mid/upper abdomen, which limits the differential diagnosis. Common causes of mid/upper abdominal pain include appendicitis, IBS, PUD, pancreatitis, inflammatory bowel disease (IBD), SBO, large bowel obstruction, acute ischemia, AAA, myocardial infarction, diabetic ketoacidosis, and gastroenteritis (Figure 3-1). Several of these diagnoses are very unlikely and need not be considered further. AAA and myocardial infarction would be exceptionally rare in this age group and gastroenteritis is very unlikely in the absence of either vomiting or diarrhea. Acute ischemia is unlikely given the absence of pain out of proportion to exam. The lack of a history of diabetes would make diabetic ketoacidosis unlikely unless this was the initial presentation. A simple blood sugar could help exclude this diagnosis. Other pivotal points in patients with abdominal pain include its time course (see Table 3-1), and if present, unexplained hypotension or abdominal distention (see Tables 3-3 and 3-4). The patient reports that this is an acute episode that has not occurred previously. This makes IBD and IBS very unlikely, focusing attention on the remaining possibilities of appendicitis, PUD, pancreatitis, and bowel obstruction. Appendicitis is the leading hypothesis as it is common and amenable to surgical cure (Table 3-5). He has neither unexplained hypotension nor distention to help focus the differential diagnosis further.

Mr. C’s symptoms are consistent with—but certainly not diagnostic of—appendicitis. He has no risk factors for any of the alternative diagnoses of pancreatitis, PUD, or bowel obstruction (alcohol use, NSAID ingestion, or prior abdominal surgery, respectively). Diagnostic options include obtaining a complete blood count (CBC) (always done but clearly of limited value), continued observation and reexamination, surgical consultation, and obtaining a CT scan. Given the lack of evidence for any of the less concerning possibilities, you remain concerned that the patient has early appendicitis. You elect to observe the patient, obtain a CBC and lipase, order a CT scan and ask for a surgical consult.

Frequent clinical observations are exceptionally useful when evaluating a patient with possible appendicitis.

The migration of pain to the RLQ is suggestive of appendicitis. Less likely considerations might include Crohn ileitis as well as diverticulitis or colon cancer (both unlikely in this age group). If the patient were a woman, PID and ovarian pathology (ruptured ectopic pregnancy, ovarian torsion, or ruptured ovarian cyst) would also need to be considered.

Diffuse abdominal pain that subsequently localizes and becomes more constant, suggests parietal peritoneal inflammation.