Joint Program in Nuclear Medicine

Radionuclide Venography of the Upper Extremity in Patients withIndwelling Venous Catheters

Gabriel Soudry, MD
Milos J. Janicek, MD, PhD

February 15, 1994

Presentation

A 23 year old man with a history of testicular cancer was receiving hemotherapy through a Port-A-Cath. Because of difficulty withdrawing blood from the Port-A-Cath, he was referred to nuclear medicine for evaluation of the patency of his central venous line.

Imaging Findings

Following bilateral arm (MPEG, 68k bytes) injection, dynamic images over the chest showed bilateral subclavian vein obstruction. Injection through the Port-A-Cath (MPEG, 59k bytes) showed prompt flow into the right heart indicating patency. However, there was hang up (27k bytes) of activity at the tip of the catheter, suggesting the presence of clot compatible with the findings after arm injection.

Discussion

Permanent indwelling central venous catheters provides a convenient mean for long term administration of total parenteral nutrition or chemotherapeutic agent, and are particularly useful when peripheral venous access sites are limited. These devices are however associated with a number of complications including venous thrombosis most likely related to the presence of a foreign body in the venous stream and the presence of a hypercoagulable state in patients with cancer. The venous obstruction may be asymptomatic or cause pain and swelling of the arm and neck. Another complication is catheter malfunction manifested as difficulty infusing through or withdrawing from the line. This is probably the result of the catheter being obstructed by a clot at the tip acting as a ball valve, a small fibrin sheath slipping over the tip, blood products or drug precipitates in the catheter lumen, or lodging of the catheter tip against the vein wall (1).

Competing Modalities:

The different modalities available for evaluation of patients with suspected catheter malfunction or venous thrombosis include the chest radiograph, radionuclide venography, contrast venography, duplex ultrasound, CT scan and MR Angiography .

Advantages of Radionuclide Venography:

The potential advantages of radionuclide venography versus contrast venography are low volume and low flow injection, no need to access a large peripheral vein, no adverse side effects, low radiation exposure (130 mrads) (2), rapidity of execution and no patient preparation. The advantages of contrast venography versus radionuclide venography are better anatomic detail and differentiation between intra and extra luminal etiologies in some cases.

Collateral pathways:

There are four important collateral routes for carrying venous blood around an obstruction and back to the right heart -- the azygos , internal mammary, vertebral, and lateral thoracic system (3). To those major pathways can be added the jugular venous arch and the contralateral brachiocephalic vein.

Technique:

The radionuclide venography is performed by injecting both arms and the central venous catheter(s) with approximately 5 mCi of technetium pertechnetate followed by a normal saline flush. The dynamic images are acquired on a large field of view camera with a high energy-low resolution collimator at the rate of two frames per seconds .

Interpretation:

In a normal study, only the deep veins of the upper extremities and the upper mediastinum should be visualized with uninterrupted flow.

A number of normal variations may be encountered including venous pooling in the subclavian vein at or before the brachiocephalic junction, sequential filling of the cephalic and basilic veins, mild reflux into the internal jugular vein, thinning at the brachiocephalic vein origin, at the confluence of the SVC and at the penetration of SVC into the pericardium (4,5).

The abnormalities detected include alteration of normal venous pathways (abrupt termination of a vessel), visualization of collateral flow suggestive of venous obstruction, persistence of tracer at the end of the line suggestive of the presence of a clot at the tip of the catheter. Extravasation of the tracer is suggestive of spontaneous migration of the catheter in the soft tissues.

The finding of prolonged transit time and/or slow flow pattern are non specific and often caused by technical factors such as site of injection, size of the vein used for injection, position of the arm, force used for saline flushing and respiratory pattern. An isolated finding of prolonged transit time may be seen in patients with right heart failure and constrictive pericarditis (5, 6).

Radionuclide versus contrast venography:

There are no large studies to compare upper extremity radionuclide venography with contrast venography, especially in cancer patients with indwelling catheters. The reason for this lack of rigorous validation may be that the upper extremity radionuclide venography is a well established technique, providing conclusive information that is rarely followed up with contrast venography. In one study performed in the Cancer Center, Houston, Texas, among 220 patients who underwent upper extremity radionuclide venography, 26 were also studied with contrast venography. There was agreement between the two techniques in 19 patients, however there was 7 false positive radionuclide venography studies. An analysis of those 7 patients revealed that 6 occurred when the slow flow pattern was the sole finding which as discussed earlier is a non specific finding (6).

Conclusions:

The radionuclide venogram is a reliable non invasive procedure for early diagnosis of venous thrombosis associated with indwelling central venous catheters.
Bilateral arm and catheter injections should be done on a routine basis to obtain complete anatomical information.
Visualization of collateral veins is the single most important criterion in the diagnosis of complete or high grade venous occlusion.
Prolonged transit time and slow flow pattern are non specific findings.

References

1. Lawson M. Partial occlusion of indwelling central venous catheters. J Intravenous Nurs 1991;14:157-59.

2. Smith E. Internal dose calculation for Tc-99m. J Nuclear Med 1965;6:231-251.

3. Hudson G. Venography in superior vena caval obstruction. Radiology 1957;68:499-505.

4. Miyamae T. Interpretation of tc-99m superior vena cavograms and results of studies in 92 patients. Radiology 1973;108:339-352.

5. Dhekne R. Upper extremity radionuclide venography in the diagnosis and management of venous disease associated with intravenous catheters. Angiology 1988;39:907-914.

6. Podoloff D,Kim E. Evaluation of sensitivity and specificity of upper extremity radionuclide venography in cancer patients with indwelling central venous catheters. Clin Nucl Med 1992;17:457-462.

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J. Anthony Parker, MD PhD, Tony_Parker@bidmc.harvard.edu