Utility of Abdominal X-ray in Appendicitis
ABSTRACT & COMMENTARY
Source: Rao PM, et al. Plain abdominal radiography in clinically suspected appendicitis: Diagnostic yield, resource use, and comparison with CT. Am J Emerg Med 1999;17:325-328.
Appendicitis is a common diagnosis in emergency medicine, and carries a lengthy differential diagnosis. Diagnostic workup often includes the use of abdominal radiographs, but clinical experience tells us that such x-rays often yield little additional or specific information. Rao and colleagues, in a retrospective chart review of patients admitted through the ED for suspected appendicitis, sought to define the diagnostic yield and cost per correct diagnosis made via plain abdominal radiography.
Between 1992 and 1996, 821 patients were admitted through the ED with suspected appendicitis. Patients ranged in age from 1 to 89 years, with a mean age of 29 years. Slightly more than half of the patients were male. A total of 524 patients (64%) had pathologically confirmed appendicitis, 114 of whom had appendiceal perforation at the time of laparotomy. Of the original group of 821 patients, 642 had abdominal radiographs performed, 396 of whom had appendicitis. Abnormal findings were noted in 51% and 47% of patients with and without appendicitis, respectively (P = 0.195). No specific radiographic finding was more likely to be found in patients with appendicitis compared to those without appendicitis. Specific radiographic diagnoses were suggested in 10% of patients; more than half of these proved incorrect compared to final clinical diagnoses. Cost analysis yielded a cost of $1,593 per correct diagnosis by plain abdominal radiography, vs. a cost of $270 per correct diagnosis by appendiceal CT.
Rao and associates conclude that plain radiography uncommonly suggests a specific and correct diagnosis in patients admitted for suspected appendicitis, and when it does, it often fails to correlate with the final clinical diagnosis. Based upon their clinical and financial analysis, Rao et al state that the use of plain abdominal radiography in this set of patients cannot be medically or financially justified.
Comment by Frederic Kauffman, MD, FACEP
All of us have learned that the classic patient with appendicitis presents first with periumbilical pain, followed by nausea, right lower quadrant pain migration, vomiting, and fever. Unfortunately, not all patients present in a classic fashion. Misdiagnosis, or delay in diagnosis, can lead to appendiceal perforation, abscess formation, and even death. As such, any adjunct to bedside evaluation that enhances diagnostic accuracy would, indeed, be very useful to patient and clinician alike.
The typical diagnostic evaluation of patients with suspected appendicitis traditionally has included history, physical examination, complete blood count, and plain abdominal radiography. Rao et al hypothesized that abdominal radiographs would yield little in patients with suspected appendicitis, and indeed they conclude just that. And though my clinical experience concurs with such a conclusion (just as it does with complete blood counts), I find it exceedingly difficult to interpret the specific data presented by the authors. For example, possible ureteral stone is listed twice in the same table on radiological impressions, with different numbers of patients for each listing. The authors differentiate between radiographic findings and overall radiological impressions; possible appendoliths occur in 48 patients as radiographic findings, but in only 24 patients as overall radiographic impressions.
As technology evolves with improvements in CT and ultrasonography, no doubt plain abdominal radiography will fall by the wayside. Confusion over data points and their analysis prevents me from using this study to invalidate totally the role of abdominal radiographs in patients with suspected appendicitis, though I believe that day is coming. In the meantime, let’s not get so hung up with diagnostic testing that we lose sight of our patients. Strong clinical suspicion of appendicitis warrants exploratory laparotomy, not a multitude of time-consuming tests. For those patients with less classic presentations, I believe that the message should be, "Don’t hang your hat on a normal, or even abnormal, abdominal radiograph."
In the study by Rao et al on plain film radiography in suspected acute appendicitis:
a. plain abdominal films are low yield.
b. plain abdominal films are recommended if the ultrasound is negative for appendicitis.
c. an appendicolith was seen in 37% of cases of appendicitis on the plain film.
d. plain films of the abdomen fared better than appendiceal CT with regard to cost-benefit analysis.
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