Abnormal gel flotation caused by contrast media during adrenal vein sampling

Abstract

Introduction: During adrenal venous sampling (AVS) procedure, radiologists administer a contrast agent via the catheter to visualize the proper catheter position.

Materials and methods: A patient with primary aldosteronism diagnostic-hypothesis was admitted for AVS. A venogram was performed to confirm the catheter's position with 2mL of Iopamidol 300 mg/mL. Samples were collected with syringe connected to a hydrophilic coated catheter by low-pressure aspiration from each of the four collection sites: inferior vena cava in the suprarenal portion, inferior vena cava in the infrarenal portion, left adrenal vein, and right adrenal vein; then immediately transferred from syringe to tubes with gel separator. All tubes were centrifuged at 1200 x g for 10 minutes.

Results: At the end of centrifugation process, primary blood tubes containing blood from inferior vena cava and left adrenal vein exhibited the standard gel separator barrier, while tubes from right adrenal vein showed abnormal flotation of gel separator. The radiologist confirmed the usage of 2.6 mL instead of 2.0 mL of Iopamidol 300 mg/mL. This iodinated contrast media, with 1.33 g/cm³ of density, was used close to the right adrenal vein due to some difficulty to access it.

Conclusion: The abnormal flotation of gel separator in samples taken from right adrenal vein can be explained by the usage of the iodinated contrast media. We suggest using plain-tubes (without gel separator) for AVS in order to avoid preanalytical nonconformities. Moreover, a blood volume equivalent to twice the catheter extension should be discarded to eliminate residual contrast media before collection of samples for laboratory assays.

Keywords: blood specimen collection; contrast media; gels; phlebotomy; preanalytical phase.

Figure 1

Abnormal gel flotation caused by contrast media during adrenal vein sampling. A – plasma sample in 3.5 mL tube with 52.5 USP U of lithium heparin and gel separator. B – serum sample in 3.5 mL serum tube with clot activator and gel separator. RAV – right adrenal vein. ICV_SR - inferior vena cava in the suprarenal portion. ICV_IR - inferior vena cava in the infrarenal portion. LAV - left adrenal vein.

Figure 2

Electropherogram of serum from peripheral venous sample. All electrophoretic fractions are within normal limits.

Figure 3

Immunofixation electrophoresis of serum from peripheral venous sample. Normal polyclonal pattern of immunoglobulins was found.