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Counter: Go Ahead with Non-Contrast CTs
Safely Saves Time and Money
by Kevin Klauer, DO
Contrast protocols, including intravenous, oral and/or rectal contrast, are just not necessary for abdominal CTs. From my perspective, the only emergent CTs that warrant IV contrast administration are CT pulmonary angiograms to identify pulmonary emboli, chest or abdominal CTs to investigate suspicion for aortic dissection and perhaps for blunt abdominal trauma.
Several studies have shown the accuracy of unenhanced or non-contrast studies. Their accuracy has been proven for almost any intra-abdominal process you could consider.
Keyzer reported in 2009 that in 131 patients, comparing oral and IV protocols to IV only, visualization of the appendix was dependant upon the reader not the protocol (AJR Am J Roentgenol. 2009 Nov;193(5):1272-81.). Beyond the concept of inter-reader variability is the fact that unenhanced studies are very accurate and are becoming more so as technology continues to improve. In 1999, Lane reported unenhanced CTs to be 96% sensitive and 99% specific for appendicitis in 300 consecutive ED patients suspected of having appendicitis (Radiology 213:341, 1999.). In 2002, the British Journal of Radiology reported the same findings in 108 patients with surgically proven appendicitis. The sensitivity of unenhanced CTs with 5mm sections was 96% sensitive and 98% specific for appendicitis (Br J Radiol. 2002 Sep;75(897):721-5.). Some have reported that with less intra-abdominal fat, visualization of the appendix is more difficult in pediatrics, necessitating contrast to discern the appendix from other structures. Hoecker, at the Children’s Hospital of San Diego, reported no difference in the accuracy of unenhanced CT, compared to findings for enhanced CTs reported by previous studies. They reported the positive and negative predictive value to be 91.3% and 90.8%, respectively.
Hill, from Michigan State University, confirmed that for all non-traumatic intra-abdominal processes, there was no statistical difference between enhanced and unenhanced studies for making the correct diagnosis (World J Surg. 2010 Apr;34(4):699-703.), and Tack reported similar findings for the diagnosis of diverticulitis (Radiology. 2005 Oct;237(1):189-96.).
Although suggesting a place for IV contrast, the use of oral contrast provides no benefit for detecting bowel or mesenteric injuries (J Trauma. 2004 Feb;56(2):314-22.). No evidence refutes the value of IV contrast for splenic and hepatic vascular injuries, reserving a place for its use in trauma.
The situation changes if the concern is for an intra-abdominal vascular catastrophe. Some clinicians mistakenly interchange the terms aortic dissection, a separation of the intima from the media, and aneurysm. Although dissections can sometimes be associated with aneurysms, these two diagnoses are very different. You can have a leaking or ruptured AAA without a dissection, and you can have a dissecting aorta without any aneurysmal dilatation. Thus, if you are looking for a dissection, you need intravenous contrast to show the false lumen (separation) between the intima and the media. Not so for aneurysms, as a dilated aorta can be easily seen without contrast. Blood from a leaking or ruptured AAA is evident without any contrast. The blood is contrast enough.
The real controversy in the use of oral and/or rectal contrast exists with abdominal/pelvic studies. Radiologists report the increased sensitivity of 64 and 128-slice MDCT scanners and warn us constantly of hypersensitivity reactions, albeit less likely with non-ionic contrast, and contrast-induced nephrotoxicity. And yet, they still want us to use contrast to “improve imaging quality.” If they want to limit the risk of acute hypersensitivity reactions and nephrotoxicity, they need to quit demanding contrast when the evidence just doesn’t support its use.
In addition to posing additional unnecessary risk to the patient, using contrast also causes substantial operational issues in every emergency department, resulting in increased throughput times, diagnostic delays and less patients being seen. For example, if an oral contrast protocol takes 90 minutes to complete (delivery, ingestion of the contrast and waiting for it to traverse the GI tract) and 10 ED patients undergo this protocol daily, a cascading effect of delays will result. Those ten protocols will cost your department 15 hours of bed time. This equates to 5,475 hours annually. If the average length of stay (all comers) is two hours, 2,737 less patients can be seen in your department annually, resulting in $273,700 less physician reimbursement (assuming an average $100 collected per patient) and $1,095,000 less revenue for the hospital in ED charges alone (assuming an average of $400 per visit for the facility/hospital side).
So if the contrast is not clinically necessary, per the research, and it’s obstructing the ED, why are we still doing it? The radiologists claim they get better results. However, their own literature suggests that they don’t. To quote Rick Bukata: If we put their own literature in a Mercedes catalog, maybe they’ll read it. The fact is that whatever marginal benefit in image quality is perceived by some Radiologists is most likely personal preference and is so minor that it doesn’t aid them in getting the right answer.
There are limitations to CT with any abdominal process. However, the use of contrast doesn’t remedy those concerns. It has been proposed that we should just order “renal stone protocol CTs” and avoid the argument altogether. I don’t advocate this approach for two reasons. First, without disclosing what pathology we are truly looking for, we are handicapping the Radiologist, impairing their ability to appropriately interpret the study. If you’re worried about appendicitis, they need to know that. The second reason is that we shouldn’t hide from this discussion. If we stop calling this practice into question, I fear it will be accepted as standard practice, resulting in delays, ED inefficiency and potential patient complications.