IQon Spectral CT in SMA Occlusion

An elderly male presented to the emergency department with vague abdominal symptoms. A conventional computed tomography (CT) scan of the abdomen and pelvis, performed with the IQon Spectral CT scanner (Philips, The Netherlands) showed hypodensities in the spleen. A color iodine map obtained with the IQon canner and superimposed on the images revealed areas of hypodensity, with no iodine uptake or splenic infarcts.

The conventional CT images and the iodine map both showed a normal-appearing proximal superior mesenteric artery (SMA). But tracking the SMA to the distal SMA clearly revealed no iodine uptake. This indicated a clot in the distal SMA, which would otherwise be difficult to detect without spectral CT.

Changing the reconstruction of the monoenergetic level to 40kV brought out the iodine and showed the SMA to be bright until reaching the distal SMA, which was completely occluded. This diagnosis would be difficult to make using only conventional imaging.

The color iodine overlay of the bowel showed no iodine uptake in the loops in the right lower quadrant. The jejunum generally has more uptake of iodine than the ileum, but in this case the distal small bowel had no uptake, indicating extensive bowel ischemia involving the distal ileum.

This patient had undergone a previous ileostomy. The splenic infarcts, bowel ischemia, and SMA clot raised concern about a potential embolic source. The patient had also had a previous sternotomy with an aortic valve replacement, as well as a coronary artery bypass graft (CABG) with a prosthetic aortic valve.

Closer examination of the left atrial appendage revealed a filling defect with no iodine uptake, indicating a thrombus that had embolized the spleen and small bowel, causing an ischemic small bowel.

The patient passed away shortly after the scan. However, this case shows the enormous power of spectral CT, not just as a diagnostic tool, but also as a “one-stop-shop” for identifying the source of the problem.