Renal Stones, Pancreatitis Require High Radiation Doses to Diagnose in the ED

Fran Lowry

December 02, 2009

December 2, 2009 (Chicago, Illinois) — A study that looked at patterns of radiation exposure from computed tomography (CT) in the emergency department of a large urban level 1 trauma center found that patients who were diagnosed with renal stone disease and pancreatitis were the most likely to receive the highest exposure to radiation from CT scans.

Cumulative effective-dose data from imaging should become part of the patient's medical record, Amita Kamath, MD, from San Francisco General Hospital and the University of California at San Francisco, said here at the Radiological Society of North America 95th Scientific Assembly and Annual Meeting.

Dr. Kamath studied cumulative exposure to radiation from CT between October 2006 and March 2007 using effective-dose estimates to determine if certain patient populations were at risk for higher levels of imaging studies and radiation.

Focusing on a retrospective review of common emergency department diagnoses — altered mental status, pancreatitis, renal stone disease, and trauma, she found that renal stone disease and pancreatitis patients had the most repeat imaging and the highest radiation exposure (50 mSv or more).

Among the 10,382 patients reviewed, 91 patients were diagnosed with renal stone disease and 61 with pancreatitis.

Overall, 28% of the cohort (2890 patients) underwent at least 1 CT scan. This ranged from 20% to 22% of patients with trauma and altered mental states, to 70% of patients with pancreatitis, to 85% of patients with renal stone disease.

A mean of 2 CT scans were performed on each patient. That number ranged from 1.8 in patients with trauma and altered mental states, to 1.4 in patients with renal stone disease, to 2.7 in patients with pancreatitis.

Overall, 4% of patients received in excess of 50 mSv. The patients most likely to receive such a high dose were those with renal stone disease and pancreatitis, Dr. Kamath said.

Patients with renal stone disease were over 60 times more likely to undergo a CT scan (odds ratio [OR], 64.6; 95% confidence interval [CI], 8.5 - 493.1) than were patients with altered mental status, and those with pancreatitis were 20 times more likely to undergo a CT scan than those diagnosed with altered mental states (OR, 21.5; CI, 7.5 - 61.7). Patients with renal stone disease were nearly 8 times more likely (OR, 7.9; CI, 1.7 - 36.0) to receive more than 50 mSv over the study period, she reported.

"I think this is often because they develop complications, such as pseudocysts or necrosis, and they end up having to get repetitive imaging," she told Medscape Radiology.

Alternative imaging modalities, such as ultrasound and magnetic resonance imaging, should be considered when such patients require a follow-up study. Limiting the number of phases within the CT itself would also limit exposure, she said.

"We have known about the risks of CT radiation exposure for a while," session moderator, Larry DeWerd, PhD, from the University of Wisconsin, Madison, told Medscape Radiology. "Now we have numbers to tell us the scope of the problem."

Heightened awareness is a good thing, he added. "The more awareness there is among radiologists, the fewer repeat exams, or at least the fewer unnecessary exams, there will be. Hopefully, this could be one of the outcomes, but of course it will take time. It won't happen overnight."

Weighing in with his opinion, J. Louis Hinshaw, MD, from the University of Wisconsin Hospital and Clinics, Madison, added: "This was very interesting work and not surprising in my experience. The use of CT in the [emergency department] has been increasing dramatically, even more so over the past 5 years or so. One of the main indications that 'needs CT in the [emergency department]' is renal stones and, if positive, there is often at least 1 follow-up examination performed, sometimes leading to large cumulative radiation doses."

He endorsed the suggestion that radiation dose should become part of the medical record.

"That is an idea that certainly has merit. There are many obstacles to overcome in order to accomplish something like that, but a national electronic medical record could make something like that possible."

Dr. Kamath, Dr. DeWerd, and Dr. Hinshaw have disclosed no relevant financial relationships.

Radiological Society of North America (RSNA) 95th Scientific Assembly and Annual Meeting: Abstract SSE22-06. Presented November 30, 2009.

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