Physical Examination

GENERAL The patient's general appearance—including facial expression, diaphoresis, pallor, and degree of agitation—provides information about the severity of pain. Although this is helpful in determining the immediacy of need for analgesia, severity of abdominal pain bears no necessary relationship to illness severity. For example, the pain of early mesenteric ischemia may be a vague discomfort, in contrast to the sudden onset of the excruciating pain of ureteral colic. Nevertheless, kidney stones have virtually no acute mortality associated with them, while the majority of patients with ischemic small bowel go on to die.

Patients with colicky pain, which is characteristically visceral due to distention of a hollow organ, are often unable to lie still, while those with peritonitis prefer to remain immobile.

VITAL SIGNS A reliable means of obtaining a core temperature is important, although absence of fever, especially in the elderly, has virtually no predictive value. Careful counting of rate and observation of depth of respirations for 15 s is often overlooked. However, it can provide crucial information about tachypnea or hyperpnea, which may be subtle. Pulse and blood pressure should include orthostatic changes if, after obtaining the history, there is any reason to suspect intravascular volume contraction. A pulse change of 30 points lying to standing at 1 min (or the development of presyncope) has been shown to be highly specific for the loss of 1 L of blood or its roughly 3-L equivalent of isotonic solute. Changes in blood pressure have not been shown to be discriminatory, probably because they are late findings that represent failure of the tachycardic response to maintain cardiac output. This threshold does not apply to patients on medications that block a tachycardic response or to the elderly, owing to the effects of aging on the cardiac conducting system.

ABDOMEN Inspection The abdomen should be inspected for distention (with air or fluid), scars, and masses.

Auscultation Contrary to conventional teaching, absent or diminished bowel sounds provide little clinically useful information. This is supported by the observation that, in a series of 100 patients with operative confirmation of peritonitis due to perforation of peptic ulcer, about half were noted to have normal or increased bowel sounds.6 Hyperactive/obstructive bowel sounds, although of limited value, are somewhat more helpful, as reflected by their presence in about half of 100 patients with small bowel obstruction (SBO), in contrast to only 5 to 10 percent of patients with 500 other surgical diagnoses. However, fully 25 percent of those with SBO had absent or diminished bowel sounds.6 It appears, therefore, that only hyperactive/obstructive bowel sounds have some clinical utility, increasing the likelihood of SBO by about fivefold; however, normal or absent bowel sounds appear very nearly valueless, as evidenced by their occurrence with roughly the same frequency in both SBO and perforated peptic ulcer.

Palpation The vast majority of clinical information obtained from examination of the abdomen is acquired through gentle palpation, using two or three fingers, beginning at a distance from the area of maximum pain. Voluntary guarding (contraction of the abdominal musculature in anticipation of or in response to palpation) can be relieved somewhat by asking patients to flex their knees. Those who remain guarded following this maneuver will often relax if the clinician's hand is placed over the patient's and the patient is then asked to use his or her own hand in palpating the abdomen. In contrast to the symptom of pain, tenderness is a sign in which pain is produced by palpation. If tenderness can be confined to a single quadrant, this is preferable. However, this is often not possible, in which case one may have to settle for tenderness encompassing one of the four combined areas noted above. Rigidity (involuntary guarding or reflex spasm of abdominal muscles) is suggestive of underlying peritoneal inflammation, as is pain referred to the point of maximum tenderness when palpating an adjacent quadrant.

"Rebound" tenderness, often regarded as the clinical criterion standard of peritonitis, has several important limitations. In patients with peritonitis, the combination of rigidity, referred tenderness, and especially, "cough pain"7 usually provides sufficient diagnostic confirmation that little is gained by eliciting the unnecessary pain of rebound.8 False positive rebound tenderness occurs in about one patient in four without peritonitis, 8 perhaps because of a nonspecific startle response. Indeed, more recent work has led some authors to conclude that rebound tenderness, in contrast to cough pain, is of "no predictive value." 9

Enlargement of the liver or spleen and other masses, including a distended bladder, should be sought. The examiner should also examine for hernias, particularly those that are tender, suggesting incarceration or strangulation. Men with abdominal pain should have a GU exam, and it is wise to maintain a low threshold for performing a pelvic examination in the evaluation of abdominal pain, particularly in women of reproductive age, regardless of where in the abdomen the pain is localized.

Although the rectal examination is widely regarded as an essential component of the evaluation of abdominal pain, particularly in suspected appendicitis, there is little evidence that rectal tenderness in patients with RLQ pain provides any useful incremental information beyond what has already been obtained by other, less uncomfortable components of the physical examination.10 The appearance of the stool—if grossly melanotic, maroon, or frankly bloody—is of value. The test for occult blood, although routinely done, loses sensitivity if not performed serially over several days; similarly, repeated rectal examination by several examiners over a period of hours tends to reduce specificity, presumably due to local trauma. In one series of patients with NSAP, 10 percent were found to have a stool positive for occult blood.11

COMPLETE BLOOD COUNT The limited clinical utility of the complete blood count (CBC) can be demonstrated most readily by examining its performance characteristics in the three most common causes of abdominal pain: Appendicitis, biliary tract disease (principally cholecystitis), and NSAP ( TableiS-^! and Table

68-3). Based upon three studies containing a total of over 1800 patients, a white blood cell (WBC) exceeding the threshold value of 10,000 to11,000/mm 3 only doubled the odds of appendicitis, while a WBC below this cut the odds in half. As noted below in the discussion of likelihood ratios (LRs), an LR(+) less than 2 and an LR(-) greater than 0.4 are of very little clinical value. For acute cholecystitis, the LRs of the WBC count are virtually identical to those seen in appendicitis and are of equally limited clinical value.

TABLE 68-2 Most Common Causes of Acute Abdominal Pain1! 34

TABLE 68-3 Causes of Acute Abdominal Pain Stratified by Age-1-L6.>34

In one large, well-conducted series of NSAP, 28 percent [95% CI 22 to 34%] of patients were reported to have WBC counts >10,500/mm 311 In an effort to develop a decision rule for the identification of NSAP, it was found that the CBC, or indeed any laboratory test, was not of value in distinguishing patients with NSAP from other, more serious diagnoses. Because of the design of studies on NSAP, it is not possible to calculate a specificity or likelihood ratio for the performance of the WBC

count in this setting. However, using 28 percent as the sensitivity of the test, it is possible to estimate that, in order for leukocytosis to be of any value in NSAP (defined as producing LRs that deviate significantly from 1), the WBC count would have to demonstrate substantially better specificity than was seen in either appendicitis or cholecystitis.

All of the above refers only to individual WBC counts. There is some evidence that serial counts may assist in the identification of appendicitis. 12 However, in this setting, it would seem wiser to obtain a more definitive test, such as a CT (see Xable...68:4) rather than risk a perforation or other complication while obtaining serial WBCs and waiting for development of a leukocytosis.

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