Low-dose CT tops plain film for imaging patients with acute abdominal pain

Low-dose CT can effectively replace plain film in cases of acute abdominal pain, with benefits for clinical diagnosis, according to a study by Swedish researchers presented at the ECR Friday afternoon.

Radiographs are commonly performed in patients with acute abdominal pain to identify bowel obstruction and free intra-abdominal gas. Radiologists know that CT is a useful tool in both of these clinical situations, but it typically requires a higher radiation dose, said Dr. Hakan Geijer, head of thoracic radiology at Örebro University Hospital. If CT could be done effectively at a lower dose, however, it could potentially replace plain film.

Researchers at Örebro compared the two techniques on 58 patients using the same low dose of 1 mSv per study - about 10% of the usual dose of a conventional CT study. CT was performed on a four-slice system at 120 kV and 20 mAs per slice. To minimize scanning time, no oral or intravenous contrast media was administered.

Three radiologists independently interpreted the studies, and clinical findings were then compared. The researchers also correlated interpretations with laboratory findings.

In most cases, the results were comparable for the two methods, but low-dose CT offered additional information that helped improve diagnosis in some patients. In three cases, for example, CT identified the causes of bowel obstruction as inguinal hernia, a low bowel obstruction, and abdominal wall hernia. Plain film missed all three. Plain film identified one case of inflamed bowel that was missed on low-dose CT. Both techniques missed a case of appendicitis.

There were no cases of free gas in the abdomen, so the study did not allow for a comparison of this common condition, which is typically imaged using plain film. During his ECR presentation, however, Geijer presented images demonstrating the utility of low-dose CT for this purpose.

Researchers concluded that low-dose CT is a viable alternative to plain film, and the university hospital now routinely uses it instead.

"Even at this very low dose, CT performs very well. We have increased our diagnostic potential with low-dose CT. However, I must stress, if you are in doubt, do not hesitate to do a full-dose CT with oral and intravenous contrast media," Geijer said.