Staten Island Corner

Popping Bottles

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It’s a busy day in the Emergency Department and you pick up a patient sent from clinic to “r/o appendicitis.” He is tachycardic and appears uncomfortable with moderate RLQ abdominal tenderness. Your attending tells you to give the patient some oral contrast to drink for the CT scan. When you arrive in the CT room to grab the contrast, you are informed that the hospital has run out.

 

Will you still be able to rule out appendicitis without oral contrast? What pathology are you missing with an unenhanced CT scan?

 

Background

Traditionally, oral (PO) contrast has been used to help better delineate the bowel from other intra-abdominal structures. There are three type of contrast based on their density compared to water. In the ED, we use positive contrast agents, which have a higher density than water, such as Gastrografin or Gastroview (1). The routine use of PO contrast can broaden the range of pathology detected (2) and its use is preferred by many radiologists.

 

Recommendations

The American College of Radiology’s (ACR) Appropriateness Criteria (https://acsearch.acr.org/list) give imaging recommendations based on patient complaint or suspected pathology. At the time of this publication, there are no ACR Appropriateness Criteria for penetrating abdominal trauma. The recommendations are graded based upon a 1-9 scale of appropriateness with 9 being most appropriate.

 

Summarized ACR Appropriateness Criteria for CT abdomen/pelvis

Indication PO contrast?
Diverticulitis Might be helpful
Nonlocalized abdominal pain + fever Yes for neutropenic patients
Maybe for appendicitis
Helpful for abscess visualization
Blunt abdominal trauma No
SBO No (contraindicated in high grade, controversial in low grade)
Appendicitis Institutional preference

 

Let’s dive deeper into the evidence behind these recommendations. For their diverticulitis recommendations, the ACR cites a study by Hill et. al, that claimed unenhanced CT was comparable to enhanced for diagnosis, however, there is a paucity of data to back that claim. That claim was based on another study that only had 4 confirmed cases of diverticulitis and in Hill et. al’s study, patients with suspected diverticulitis were actually excluded. While the data for unenhanced CT scan for diverticulitis is lacking, the ACR provided much better evidence for rectal contrast in the diagnosis of diverticulitis, demonstrating excellent sensitivity (97%) and specificity (100%) (3).

As the spectrum of disease in the patient with nonlocalized abdominal pain and fever is so broad, finding high quality studies to support a recommendation is difficult. The ACR recommendations tend to favor oral contrast administration. The recommendations vary based on the population under investigation, as well, such as postoperative vs. pregnant vs. immunocompromised. For instance, in neutropenic patients, they cite studies looking at cancer or AIDS patients, all of whom received oral and IV contrast for their CT scans, so a determination of the necessity of PO contrast is impossible in these patients. For ICU patients with sepsis of unknown origin a study by Barkhausen et. al with n = 45 is cited that administered oral and IV contrast to all patients and was able to find a source in 15.6% of patients on CT abd/pelvis. Some studies make no mention of whether or not oral contrast was used, making further interpretation impossible.

The evidence presented by the ACR for SBO, blunt abdominal trauma, and appendicitis all trend toward no significant difference in CT diagnoses made between PO contrast enhanced and nonenhanced CT scanning. The ACR hedged their bets by recommending institutional preference for oral contrast use in evaluation of appendicitis and a 2010 ACEP clinical policy (4) recommends the use of CT scan, but simply states that using any contrast can increase sensitivity. Upon further evaluation of the data behind their recommendations, the indecisiveness appears to stem from the fact that while the majority of the literature shows no significant difference without oral contrast, there are a few well-designed studies that show statistically significant increased detection of appendicitis with oral contrast. Since the publication of these recommendations, there has been a number of additional studies specifically questioning the utility of oral contrast. Most reach the conclusion that oral contrast is not needed (5, 6).

There are several other patient populations that may not require oral contrast. In patients with a suspected internal hernia or suspected intramural hematomas, oral contrast may actually hinder evaluation (2, 7).  Some studies suggest that obese patients may not require PO contrast as their increased intraabdominal fat serves as contrast material. One study evaluated 46 patients by 2 radiologists, which found increasing Kappa values with increasing BMI as far as which patients did not require oral contrast (8). A larger retrospective study looked at whether omission of oral contrast in patients with BMI >25 would result in any delayed or missed diagnoses and they found none out of the 375 patients did (9). However, a more rigorous prospective observational trial of 100 patients looking at concordance of patients scanned with and without PO contrast found significant disagreement between scans (10) and another study found that increasing BMI or intraabdominal fat had no effect on appendiceal visualization (11). Given the inconsistency between these results there is not enough evidence to say with certainty that obesity precludes the necessity of PO contrast.

 

When should my patient definitely be drankin?
Finding solid evidence on specific pathology that would require PO contrast proved difficult. Logically, detecting perforations, bowel leaks, sinus tracts, or fistulae should be aided by the use of PO contrast, and this has been the classic teaching (1, 12, 13), but I could not find any studies evaluating these without oral contrast. Nor was I able to find any study that evaluated penetrating abdominal trauma with and without oral contrast. The main concerns with penetrating trauma are hollow viscus or vascular injury, which would be best evaluated using contrast. The “triple contrast” study with IV, oral, and rectal contrast appears to be both highly sensitive and specific in penetrating abdominal/pelvic trauma (14, 15, 16, 17) and appears to be the radiological exam of choice for stable patients.

 

Why should I even care about oral contrast?
When it comes to patient satisfaction in the ED, the decision whether or not to administer oral contrast to a patient is an important one to consider. Oral contrast is not exactly a palatable beverage, and in a nauseous, vomiting patient with abdominal pain, it is a bit cruel and unusual to ask them to guzzle a liter of the foul tasting fluid. Furthermore, drinking all of that oral contrast puts the patient at risk of aspiration. As if that wasn’t bad enough, a small study demonstrated that positive enteric contrast may actually significantly increase the amount of radiation exposure (by about 11%) a patient receives compared to a scan with just water (18).

In the Emergency Department, efficiency is crucial to providing quality care and to ensure that resources are available when critically ill patients roll in. If oral contrast is not needed for a CT scan, median ED LOS may be 43 to over 200 minutes shorter leading to more expedient diagnosis and disposition (6, 19, 20), depending on the amount of time your institution normally has the patient wait after drinking oral contrast. Of the two studies that tracked such data, only one patient had a repeat CT with oral contrast that changed the initial impression for a combined rate of approximately 0.02%. In addition to the time saved, oral contrast adds cost to the patient’s stay both directly and indirectly through increased need for anti-emetics, nursing care, and ancillary supplies.

TL;DR

Eden’s Recommendations

Indication Oral Contrast?
Blunt abdominal trauma, SBO Say NO to PO
Appendicitis, diverticulitis I came to the fork in the road and went straight (21)
Nonlocalized abdominal pain + fever

 

Immunocompromised abdominal pain

 

Concern for fistula, leak, or perforation

Chug! Chug! Chug!

 

References:

  1. Sandrasegaran, K., & Kambadakone, A. (2011). CT Protocols for Abdomen and Pelvis. In Abdominal Imaging (pp. 93-101). Elsevier.
  2. Kammerer S, Höink A, Buerke B, et al. Abdominal and pelvic CT: is positive enteric contrast still necessary? Results of a retrospective observational study. European Radiology [serial online]. March 2015;25(3):669-678.
  3. Rao PM, Rhea JT, Novelline RA, et al. Helical CT with only colonic contrast material for diagnosing diverticulitis: prospective evaluation of 150 patients. AJR Am J Roentgenol. 1998;170(6):1445-1449.
  4. Howell J, Eddy O, Lukens T, Thiessen M, Weingart S, Decker W. General medicine/clinical policy: Clinical Policy: Critical Issues in the Evaluation and Management of Emergency Department Patients With Suspected Appendicitis. Annals Of Emergency Medicine [serial online]. January 1, 2010;55:71-116.
  5. Glauser J, Siff J, Emerman C. Emergency department experience with nonoral contrast computed tomography in the evaluation of patients for appendicitis. Journal Of Patient Safety [serial online]. September 2014;10(3):154-158.
  6. Levenson R, Camacho M, Horn E, Saghir A, McGillicuddy D, Sanchez L. Eliminating routine oral contrast use for CT in the emergency department: impact on patient throughput and diagnosis. Emergency Radiology [serial online]. December 2012;19(6):513-517.
  7. Hongo N, Mori H, Matsumoto S, Okino Y, Takaji R, Komatsu E. Internal hernias after abdominal surgeries: MDCT features. Abdominal Imaging [serial online]. August 2011;36(4):349-362.
  8. Harrison M, Lizotte P, Holmes T, Kenney P, Buckner C, Shah H. Does high body mass index obviate the need for oral contrast in emergency department patients?. The Western Journal Of Emergency Medicine [serial online]. November 2013;14(6):595-597.
  9. Alabousi A, Patlas M, Sne N, Katz D. Trauma and Emergency Room Imaging / L’imagerie des urgences et des traumatismes: Is Oral Contrast Necessary for Multidetector Computed Tomography Imaging of Patients With Acute Abdominal Pain?. Canadian Association Of Radiologists Journal [serial online]. January 1, 2015
  10. Wolfe J, Smithline H, Lee S, Coughlin B, Polino J, Blank F. Original Contributions: The impact of body mass index on concordance in the interpretation of matched noncontrast and contrast abdominal pelvic computed tomographic scans in ED patients with nontraumatic abdominal pain. American Journal Of Emergency Medicine [serial online]. January 1, 2006;24:144-148.
  11. Anderson S, Rhea J, Milch H, Ozonoff A, Lucey B, Soto J. Influence of body habitus and use of oral contrast on reader confidence in patients with suspected acute appendicitis using 64 MDCT. Emergency Radiology [serial online]. November 2010;17(6):445-453.
  12. Girard E, Messager M, Mariette C, et al. Review: Anastomotic leakage after gastrointestinal surgery: Diagnosis and management. Journal Of Visceral Surgery [serial online]. December 1, 2014;151:441-450
  13. Tirumani S, Shinagare A, Jagannathan J, Krajewski K, Ramaiya N. Multidetector-row CT of tumour–bowel fistula: Experience at a tertiary cancer centre. Clinical Radiology [serial online]. February 1, 2014;69:e100-e107.
  14. Albrecht R, Vigil A, Schermer C, Demarest G, Davis V, Fry D. Stab wounds to the back/flank in hemodynamically stable patients: evaluation using triple-contrast computed tomography. The American Surgeon [serial online]. July 1999;65(7):683-687.
  15. Shanmuganathan K, Mirvis S, Chiu W, Killeen K, Hogan G, Scalea T. Penetrating torso trauma: triple-contrast helical CT in peritoneal violation and organ injury–a prospective study in 200 patients. Radiology [serial online]. June 2004;231(3):775-784.
  16. Múnera F, Morales C, Velez G, et al. Gunshot wounds of abdomen: evaluation of stable patients with triple-contrast helical CT. Radiology [serial online]. May 2004;231(2):399-405.
  17. Lozano D, Munera F, Anderson SW, Soto JA,  Menias CO, and  Caban KM. Penetrating Wounds to the Torso: Evaluation with Triple-Contrast Multidetector CT. RadioGraphics Mar-Apr 2013 33:2, 341-359.
  18. Wang Z, Chen K, Gould R, Coakley F, Fu Y, Yeh B. Positive enteric contrast material for abdominal and pelvic CT with automatic exposure control: what is the effect on patient radiation exposure?. European Journal Of Radiology [serial online]. August 2011;79(2):e58-e62.
  19. Huynh L, Coughlin B, Wolfe J, Blank F, Lee S, Smithline H. Patient encounter time intervals in the evaluation of emergency department patients requiring abdominopelvic CT: oral contrast versus no contrast. Emergency Radiology [serial online]. July 2004;10(6):310-313.
  20. Razavi S, Johnson J, Kassin M, Applegate K. The impact of introducing a no oral contrast abdominopelvic CT examination (NOCAPE) pathway on radiology turn around times, emergency department length of stay, and patient safety. Emergency Radiology [serial online]. December 2014;21(6):605-613.
  21. Cappadonna. Slang Editorial. 1998. CD.
The views expressed on this blog are the author's own and do not reflect the views of their employer. Please read our full disclaimer here. Any references to clinical cases refer to patients treated at a virtual hospital, Janus General Hospital.
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1 comment for “Popping Bottles”

  1. wendyrollerblades
    July 20, 2015 at 5:48 pm

    Great post! It will give me some ammo for when I argue for or against PO contrast for a scan.

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