imageChicago—Enteral contrast does not diagnostically benefit patients undergoing appendectomies, according to a study of a majority of patients in Washington state who had this procedure over a two-year period.

As a result of their findings, researchers said that the addition of enteral contrast to IV contrast should not be considered necessary when computed tomography (CT) is performed for suspected appendicitis. Physicians and hospitals participating in SCOAP (Surgical Care and Outcomes Assessment Program), the voluntary collaborative of surgeons in Washington that led the study, will be encouraged to use CT scans enhanced only by IV contrast material when patients are undergoing evaluation for appendicitis.

“Comparable effectiveness can be achieved using IV contrast alone in CT scans for suspected appendicitis,” said lead author Frederick Thurston Drake, MD, a surgery resident and fellow at the Surgical Outcomes Research Center, University of Washington, Seattle. He presented the findings at the 2012 American College of Surgeons’ Annual Clinical Congress.

However, surgeons stressed that the study did not take into account the patients who, after receiving the contrast, were diagnosed with pathology other than appendicitis and ultimately did not undergo appendectomy. In other words, the patients who, arguably, derived the greatest benefit from enteral contrast were excluded from the study. “That is a significant weakness,” said Benjamin Braslow, MD, associate professor of surgery and chief of the emergency surgery service, University of Pennsylvania School of Medicine, Pittsburgh.

However, the authors said that the study was designed to demonstrate real-world results and that earlier, randomized trials demonstrated no benefit in the use of oral contrast (Radiol Technol 2011;82:294-299).

The study was based on data collected by SCOAP, which represents 60 hospitals in Washington state. Dr. Drake and his colleagues studied consecutive cases of appendicitis at the 58 hospitals that had signed on to SCOAP by the time of the study.

Over a two-year period, 9,047 patients underwent nonelective appendectomy, representing 85% of nonelective appendectomies performed in the state at that time. In the study group, 89% of patients had a CT scan before surgery. Almost half (52%) of the patients received IV contrast before the CT, whereas 27% had IV contrast and some form of enteral contrast. In almost all cases where patients received enteral contrast (97%), the contrast was administered orally. A minority of patients received no type of contrast or enteral contrast alone. Concordance between radiology and pathology was approximately 90%, regardless of contrast regimen.

Analysis showed that patients who received enteral contrast rather than IV contrast alone had slightly higher rates of perforations (17.4% vs. 14.7%, respectively; P=0.005), higher rates of negative appendectomy (3.5% vs. 2.7%; P=0.046), and longer duration between their admission to the emergency department and the beginning of surgery, waiting an average of 9.1 hours compared with 8.3 hours (P<0.001). The authors said that they do not believe the type of contrast administered led to any differences in the rate of perforations.

Currently, no clear standard exists on the use of enteral contrast before an abdominal-pelvic CT scan in cases of suspected appendicitis. Critics pointed out that enteral contrast comes with a host of disadvantages: It is time-consuming, unpleasant for patients and may be a risk factor before general anesthesia. Moreover, in as many as one-third of patients, the enteral contrast fails to reach the cecum.

image Conversely, proponents argue that enteral contrast can help identify the appendix, or any other pathology. “I don’t think that PO [positive oral] contrast is always necessary to make the diagnosis of an acute appendicitis but, if you’re wrong about the diagnosis, especially in female patients where there is other potential pathology in the region, the presence of PO contrast gives you important information,” Dr. Braslow said.

The study was not powered to show that enteral contrast led to higher rates of perforations, negative appendectomies or long waits before surgery. However, investigators said that the study failed to show a single benefit for enteral contrast over IV contrast alone and that, along with their findings, recent randomized trials in radiology literature suggest “comparable effectiveness.” They also pointed out that patients were not randomized to one contrast type or another, potentially introducing selection bias, and final radiology reports were used to determine concordance.

Earlier studies supported the use of enteral contrast, showing that it led to improved diagnostic accuracy. But many of those studies relied on early generation scanners, said Dr. Drake. With today’s 64-multidetector helical scanners, more recent studies suggest the oral contrast is not of added benefit (Radiol Technol 2011;82:294-299).

However, Dr. Braslow said that the SCOAP study is not sufficient to convince him to cease the use of enteral contrast. “Using IV contrast alone is an interesting concept that has been discussed for a long time. There is a lot of information missing in this study, [for instance] the patients who did not undergo appendectomy and the time from a [patient’s admission to] the emergency room to having a CT scan. We need these things explained.”

He added that emergency doctors often make the call on the type of contrast used for a patient with suspected appendicitis.

The study showed that hospital characteristics did not influence the use of enteral contrast. Rates were similar across urban and rural hospitals, and for hospitals with and without surgical residency programs.

Hospitals that participated in SCOAP were not required to stop the use of enteral contrast as a standard for patients with suspected appendicitis. Avoiding enteral contrast, however, will be set as a “best practice” benchmark across SCOAP hospitals. Surgeons, emergency room doctors and radiologists will receive quarterly reports that track the use of enteral contrast and monitor changes in practice.

“Ultimately, we’ll be tracking quarter-by-quarter use of enteral contrast, and concordance, to make sure we’re improving. This is how we cut the translation of evidence into practice from years to months,” Dr. Drake said.