Why We Do What We Do: Do We Really Need Contrast CT Scan for Acute Appendicitis?

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Surgical Validation of Unenhanced Helical Computed Tomography In Acute Appendicitis.

 

 

My_name_is_APPENDIX_20140223_MynameisAPPENDIXImage courtesy of google images: funnyand.com 

 

by: Sarah Goldman, MD, PGY-2

Bottom Line:

 

Plain helical CT (without PO or IV contrast) has a sensitivity of 95.4% and specificity of 100% in diagnosis of acute appendicitis.

 

Major points:

Appendicitis carries a lifetime risk of 8.6% for males and 6.7 for females. Currently the diagnosis of appendicitis is aided by the use of helical CT; however, necessity of oral and/or IV contrast is controversial.  In this study, “Surgical validation of unenhanced helical computed tomography in acute appendicitis” 103 patients diagnosed clinically with appendicitis underwent an unenhanced CT scan of the abdomen and pelvis followed by emergency laparoscopy.  CT scan diagnosed appendicitis in 83 patients (80·6 per cent); laparoscopy identified 87 patients with appendicitis (84·5 per cent). Prospective interpretation of CT images yielded a sensitivity of 95·4 per cent and a specificity of 100 per cent for the diagnosis of acute appendicitis. There were four false-negative scans, including a missed perforated appendicitis.

 

Design:

  • Multicenter, prospective study
  • N=103 patients; all underwent CT and laparoscopy
  • Setting: University Hospital Rotterdam and Medical Centre Rijnmond-Zuid
  • Enrollment: December 1999 and November 2001
  • Primary outcome: diagnosis of appendicitis

 

Inclusion Criteria:

  • Age 16 or older
  • Clinical diagnosis of acute appendicitis by senior surgeon

 

Exclusion criteria:

  • signs of acute bowel obstruction
  • contraindication to laparoscopy
  • contraindication to general anesthesia
  • pneumoperitoneum
  • age under 16 years
  • pregnancy
  • sepsis (body temperature of 39°C or above or 35·5°C or less and dependence on catecholamines to maintain normal blood pressure, or positive blood cultures).

 

Method:

  • Clinical diagnosis of appendicitis established by senior surgeons
  • All patients subsequently underwent both unenhanced abdominal CT* and standardized diagnostic laparoscopy
  • laparoscopy divided into two phases: exploratory and diagnostic. During exploratory phase surgeon was blinded to CT findings. Results were used to interpret value of preoperative CT.  The surgical findings elucidated during exploratory phase of laparoscopy were considered the gold standard
  • All scans were reviewed by radiologists blinded to the clinical history and surgical findings

 

Results:

  • Diagnosis of appendicitis on CT:  appendix greater than

–         appendix >6 mm in transverse diameter.

–         Secondary signs were:

periappendiceal infiltration, thickening of the caecal wall,

presence of an appendicolith, periappendiceal phlegmon or abscess, and adenopathy

– Scans were considered positive if only secondary signs were noted

  • Acute appendicitis was diagnosed by laparoscopy 87 of 103 pts (84.5%)
  • Acute appendicitis was diagnosed by unenhanced CT in 83 of 103 pts (80.6)
  • Sensitivity of unenhanced CT was 95.4; specificity 100%.
  • There were four false negative scans; three cases involved only the tip of appendix and one perforated appendicitis with microabscess

 

Criticism:

  • Despite that the CTs were reviewed by both residents and expert radiologists, only the scores by expert radiologists were used to evaluated performance of preoperative CT. The correlation between final results of radiology residents vs. experts is unknown
  • Number of patients studied is relatively small
  • False negative did include a case of perforated appendicitis with microabscess
  • Small study and further research is needed before this can become a routine part of the diagnostic work-up.

 

References:

Van Lankeren, W., et al. “Surgical validation of unenhanced helical computed tomography in acute appendicitis.” British journal of surgery 91.12 (2004): 1641-1645.

 

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