Journal Club

Journal Club: CT Scans in the ED Abdominal Pain Patient – Role of PO Contrast?

For this monthʼs journal club we looked at the role of oral contrast in the evaluation of abdominal pain. Overall we found that omitting oral contrast can lead to accurate diagnosis while decreasing ED length of stay and decreasing time to the OR.

Taken together, these studies stand as evidence against the routine use of oral contrast. Additionally, non oral contrast CT studies aid in reaching a diagnosis and disposition faster than when oral contrast is administered.

Article #1:

The first article we reviewed was A systematic review of whether oral contrast is necessary for the computed tomography diagnosis of appendicitis in adults by Anderson et al. It was published in The American Journal of Surgery, 2005. This systematic review aimed to evaluate “the diagnostic performance of CT with and without contrast.” Twenty-three studies were included in the final analysis. Overall, CT with and without contrast did show excellent sensitivity (83–97%) and specificity (93–98%). Data was then analyzed by two subgroups: CT with oral contrast vs CT without oral contrast. The oral contrast group included studies that utilized only oral contrast, oral and rectal contrast, and IV contrast alone. The data for the CT scans without oral contrast combined studies utilizing rectal contrast and non-contrast studies, thus a mode of enteral contrast was still included in this subgroup. The authors concluded that CT without oral contrast can actually improve specificity (97% vs 94%), PPV (97% vs 89%), and accuracy (96% vs 92%) when compared to studies that utilized oral contrast. However, the authors combined groups are composed of individual studies that are far to heterogeneous to confidently assess whether non-oral contrast CT is superior to oral contrast CT. One would need a prospective comparative trial to more confidently make this assessment. Overall this paper did a good job of highlighting the excellent utility of CT in diagnosing appendicitis with or without contrast enhancement.

Article #2

The next paper we looked at was Intravenous contrast alone vs intravenous and oral contrast computed tomography for the diagnosis of appendicitis in adult ED patients by Kepner et al. This paper was published in The American Journal of Emergency Medicine in 2012. This was a prospective randomized trial aimed to compare IV contrast only to IV and oral contrast (IVO) in the evaluation of acute appendicitis. The study included adults presenting to a single academic ED with suspected appendicitis. There were 227 patients included in the final analysis. Both IV and IVO scans had 100% sensitivity and negative predictive value for appendicitis. Specificity of IV and IVO scans was 98.6% and 94.9%, respectively. Patients who received IV only scans were dispositioned from the ED about 1.5 hours faster, or made it to the OR over one hour faster when compared to those who had IVO scans. The authors concluded that IV and IVO CT studies have comparable diagnostic utility in the evaluation of appendicitis. The greatest limitation to this study was that the real-time radiological interpretation was not used. There were designated “study radiologist” who independently read the CT for the purpose of diagnosing appendicitis. Additionally, this study falls short of demonstrating whether the findings are reproducible and generalizable in other settings. Overall, this is a well designed study that demonstrates the advantages of omitting oral contrast for the evaluation of appendicitis in patients presenting to the ED.

Article #3

The next study we reviewed was Eliminating routine oral contrast use for CT in the emergency department: impact on patient throughput and diagnosis by Levenson et al. This study aimed to assess the effect of introducing a CT protocol that eliminated routine oral contrast for CT evaluation of undifferentiated abdominal pain in adult patients presenting to an urban, tertiary care ED. This was a retrospective analysis that looked at patients undergoing CT in the emergency department in the two months preceding the change in protocol and in the two months following the change. As per the new protocol, patients with inflammatory bowel disease, prior gastrointestinal tract- altering surgery, or lean body habitus continued to receive oral contrast. In total, 2,001 patients underwent CT during the study period: 1,014 before and 987 following the change in protocol. The use of oral contrast decreased from 95% of eligible patients to 42% after initiation of the new protocol. The authors found that the median ED length of stay decreased by approximately 1.5 hours. After initiation of the new protocol, four patients underwent repeat CT utilizing oral contrast. None of these repeat scans resulted in a change in diagnosis. The authors concluded that by eliminating routine use of oral contrast, patients can reach disposition faster without a compromise in diagnosis. One limitation to this study is that their is no comment as to whether IV contrast was administered or if the patients simply received no contrast at all. In addition, they did not comment on clinical outcomes or if surgical pathology confirmed CT diagnosis when appropriate. Overall though, this paper does a great job of highlighting the effects of faster throughput without compromise in diagnosis through elimination of routine use of oral contrast.

Effectiveness in a Prospective Surgical Cohort, by Drake et al, published in the Annals of Surgery, 2014. This study sought to compare the effectiveness of IV vs IV and enteral contrast for the diagnosis of appendicitis. Data was collected prospectively for patients who underwent CT imaging prior to nonelective appendectomy at 56 hospitals in the state of Washington. Concordance between final pathology and radiological interpretation was the final outcome. Rural, urban, teaching and non-teaching hospitals were included in the study. There was no difference in concordance with pathology findings for patients undergoing CT with IV and enteral contrast (90.0%) and in those who received IV contrast alone (90.4%). Additionally, there was no difference in concordance when analyzed by hospital type. As in prior studies, an increased time to OR was noted in patients who received enteral contrast when compared to those who received only IV contrast. One limitation to the study, is that it is possible that physicians with the highest clinical suspicion for acute appendicitis may have opted against the extra step of oral contrast, thus biasing the data. Overall thou, this paper does a great job of demonstrating 1) concordance between IV only CT and pathologic diagnosis of appendicitis and 2) that these findings are actually applicable in diverse practice settings.

References:

  1. Anderson BA, Salem L, Flum DR. A systematic review of whether oral contrast is necessary for the computed tomography diagnosis of appendicitis in adults. Am J Surg. 2005;190:474-478
  2. Kepner AM, Bacasnot JV, Stahlman BA. Intravenous contrast alone vs intravenous and oral contrast computed tomography for the diagnosis of appendicitis in adult ED patients. AJEM. 2012;30:1765–1773.
  3. Levenson RB, Camacho MA, Horn, E, et al; Eliminating routine oral contrast use for CT in the emergency department: impact on patient throughput and diagnosis. Emerg Radiol 2012;19:513-517
  4. Drake FT, Alfonso R, Bhargava P, et al.Enteral Contrast in the Computed Tomography Diagnosis of Appendicitis Comparative Effectiveness in a Prospective Surgical Cohort. Annals of Surgery 2014;260:311-316.
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