Venous contrast fluid level in computed tomography

To evaluate the clinical significance of a venous contrast fluid level during computed tomography (CT).

An incidentally found contrast fluid level in the left internal jugular vein during CT in an otherwise healthy patient was the reason for investigation of this phenomenon. We collected data over a 4-year period at our institution and reviewed the case notes of seven patients exhibiting this CT finding. We also performed conventional radiography, CT, venography and colour-coded Doppler sonography to rule out an underlying pathology in those patients. Additional in-vitro CT studies were performed to define conditions of flow leading to a contrast fluid level. Flow dynamics in the internal jugular veins were studied in vivo by using colour-coded Doppler sonography in 20 normal volunteers.

In addition to our first patient, we found seven patients with a venous contrast fluid level among a total of 58400 contrast-enhanced CT examinations performed in our institutions. The investigations were performed on various CT-units, with different scan protocols, injection rate, dose and manufacturer of non-ionic contrast agent. The contrast fluid level was encountered unilaterally in the left internal jugular vein in seven patients and in the inferior vena cava in one patient. All patients were free of symptoms and the outcome of all other examinations was unremarkable. In-vitro and in-vivo studies showed that pure contrast agent entering a vessel (in case of the internal jugular vein due to physiological flow and/or stasis) can produce a contrast fluid level.

The occurrence of a venous contrast fluid level during contrast enhanced CT is an incidental finding of no pathological significance and need not initiate costly further examinations.