CT Diagnosis of Acute Appendicitis
March 1, 1998 3 minutes read
ABSTRACT & COMMENTARY
Fifty-three patients had APPDX and 47 had alternative diagnoses, including mesenteric adenitis, nonspecific abdominal pain, ovarian cyst, right-sided colitis, sigmoid diverticulitis, and biliary colic. Eighty-six patients had a specific clinical diagnosis; the CT scan revealed this diagnosis in 81 cases. The clinical syndromes not diagnosed by CT scan included biliary colic (2), urinary tract infection (1), endometriosis (1), and appendicitis (1); the remaining patients were ultimately diagnosed with nonspecific abdominal pain and presumably did well at follow-up.
The appendiceal CT was 98% sensitive and 98% specific for the diagnosis of APPDX; the CT scan also demonstrated a 98% positive predictive value, a 98% negative predictive value, and an overall accuracy rate of 98% for the diagnosis of APPDX. In the entire study population, the CT scan provided a false negative result in only one patient. The CT scan findings led to changes in the intended treatment plan for 59 patients, including the prevention of unnecessary surgery (13), admission to the hospital for observation (18), admission to the hospital for preoperative monitoring prior to appendectomy (21), and admission to the hospital for additional evaluation and treatment of other conditions (11). Considering the costs of the CT scan, unnecessary surgery, and unnecessary admission, Rao et al reported an overall savings of $447 per patient. (Rao PM, et al. Effect of computed tomography of the appendix on treatment of patients and use of hospital resources. N Engl J Med 1998;338:141-146.)
COMMENT BY WILLIAM J. BRADY, MD
In most cases, acute appendicitis does not represent a diagnostic challenge; approximately 70% of cases of APPDX are reasonably straightforward and are correctly made prior to surgery. The remaining 30% of cases present with some atypical or challenging features, such as young patient age, unusual pain location, or prolonged/intermittent pain. Patients in this presentation category are not infrequently misdiagnosed on initial contact in the ED. These patients with delayed diagnosis are at extreme risk of perforation with significant associated morbidity. Further, missed APPDX is the leading successful malpractice claim against emergency physicians in the United States.Rao et al provide yet another useful tool to the emergency physician
and consultant surgeon in the acute evaluation of the patient with abdominal
pain and possible APPDX. The CT scan, however, probably is not indicated
in the majority of cases of APPDX, as most cases do not present a diagnostic
challenge. The CT scan will probably be most useful in the questionable
case. The use of CT scan in this type of patient will assist in several
ways; it can 1) "rule-in" APPDX; 2) "rule-out" APPDX and provide, in many
cases, the alternative diagnosis; 3) limit the number of unnecessary laparotomies;
and 4) suggest the appropriate therapy in the early stages of ED evaluation.
One would hope that the CT scan would not become a standard investigation
in the evaluation of all patients with lower abdominal pain; rather, its
most appropriate use will likely be found in the patients with an atypical
or questionable presentation. Lastly, among experienced general radiologists
with minimal instruction, interpretation of the scan reportedly is not
problematic; the issue of operator expertise, a problem with the use of
ultrasound in the evaluation of possible APPDX, will not introduce limitation
to its use.
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