Diagnostic Accuracy for Appendicitis, Alternative Diagnoses

February 2006

February 2006 Emergency Medicine Journal Club Vignette

Listening to Emergency Medicine Abstracts’ while driving home from another ED shift, you listen with interest as they begin discussing a paper about the lack of utility of oral contrast in the diagnostic evaluation of children with suspected appendicitis.  Your just completed shift was marked by a 20 year old non-pregnant female with acute onset of non-specific abdominal pain 3-hours prior to ED presentation which was primarily right lower quadrant pain upon your evaluation.  Lacking fever, peritoneal signs, anorexia, or a compelling alternative diagnosis you had ordered a CT scan from Radiology.  The busy Radiology resident had requested that you consult Surgery to determine the utility of a CT in a reproductive age female.  Unfortunately, General Surgery is in the operating room for the next 3 hours and when they finally arrive to hear the story and evaluate the patient, the opine that “all abdominal pain patients with suspected appendicitis should obtain a CT before surgery consult to confirm the diagnosis”. 

You notify Radiology of this delayed discussion and the Radiology resident next requests oral contrast be administered, further delaying the imaging which finally occurs 6-hours after the initial ED evaluation and 9-hours after symptom onset.  Appendicitis is confirmed by CT and histology, but you wonder why the diagnostic evaluation had to be so delayed.  You listen intently to the “Rick & Jerry Show” and then vow to perform your own analysis of the literature.

PICO Question: 

Population:  Adults (over age 18) presenting to ED with concern for appendicitis

Intervention:  CT abdomen without oral contrast

Comparison:  CT abdomen with oral contrast

Outcome:  Diagnostic accuracy for appendicitis, alternative diagnoses

Search strategy:  Utilizing OVID (1996 to present) you enter the search terms computed tomography AND appendicitis which yields 248 articles.  The fifth article on that list is a Systematic Review which provides you with the remainder of the articles you elect to analyze.  You also include an additional article provided to you by the Radiology resident that night which evaluates this question in children.

First YearsSuspected Appendicitis in Children:  Diagnosis with Contrast-enhanced versus Nonenhanced Helical CT.   Radiology 2004; 231:  427-433. Answer Key

Second YearsDiagnostic Value of Unenhanced Helical CT in Adult Patients with Suspected Acute Appendicitis.  Brit J Radiology  2002; 75:  721-725. Answer Key

Third YearsSuspected Acute Appendicitis:  Nonenhanced Helical CT in 300 Consecutive PatientsRadiology 1999; 213:  341-346. Answer Key

Fourth YearsA Systematic Review of Whether Oral Contrast is Necessary for the Computed Tomography Diagnosis of Appendicitis in Adults.  Am J Surg 2005; 190:  474-478. Answer Key

1st, 2nd, & 3rd use the Diagnosis Critical Review Form

  4th use the Meta-Analysis Critical Review Form

Bottom Line

Children and thin adults probably benefit from the use of oral contrast when evaluating for appendicitis with CT imaging.  Although unenhanced abdominal CT’s are probably equal to contrast (IV + PO, rectal + oral, oral alone, rectal alone) in diagnosing acute appendicitis, Emergency Medicine physicians should be aware of the observed learning curve with more false-negative interpretations at the beginning on non-contrast protocols.  Additionally, clinicians should be aware of the increased likelihood of false-negative interpretations in very early appendicitis.  A more rigorous Systematic Review might identify additional studies to alter these recommendations, but current best-evidence suggests that in adults who are not thin physicians might expedite the clinical course while decreasing patient suffering and perforation rates by the utilization of non-contrast CT imaging if their Radiologists have experience with these evaluations.