Keywords
Denver shunt - pleurovenous shunt - hepatic hydrothorax - nonmalignant pleural effusion
- interventional radiology
The LeVeen shunt was introduced in 1974 as a device to shunt ascitic fluid into central
venous circulation through a unidirectional valve by exploiting elevated pressures
in the peritoneal cavity with respect to the superior vena cava.[1] Years later in 1979, the Denver shunt was introduced, which incorporated a subcutaneous
pump that could be manually compressed to facilitate passage of fluid against higher
pressures. The first described use of the Denver shunt for managing symptomatic pleural
effusion was published in 1980.[2] Currently, single-valve and bi-valve Denver shunt systems are commercially available
(BD CareFusion, San Diego, CA). The shunt system consists of the pump chamber, a 15.5-Fr
multi side-hole drainage catheter, and a single end-hole venous catheter. A smaller
11.5-Fr venous limb is also available and recommended for use if the subclavian vein
is accessed rather than the internal jugular.[3] The single-valve system is marketed as being more favorable for the drainage of
viscous fluid due to decreased obstruction to flow.[3] The bi-valve system allows patients to pump the shunt repeatedly without having
to compress the venous limb between pumps while the chamber refills.
Patient Selection
In the United States, pleural effusions affect over a million patients annually, with
many experiencing debilitating symptoms and poor quality of life.[4] Causes of recurrent, nonmalignant pleural effusion include congestive heart failure,
hepatic hydrothorax, chylothorax, hypoalbuminemia, nephrotic syndrome, and idiopathic
recurrent effusion, among others.[4]
[5] Cirrhotic patients with portal hypertension, ascites, and hepatic hydrothorax are
frequently encountered by interventional radiologists. Approximately 85% of hepatic
hydrothorax cases are right-sided and are thought to occur due to transgression of
ascitic fluid through small defects in the diaphragm, although other hypotheses have
also been postulated.[6] When refractory to medical therapy with dietary salt restriction and diuretic use,
therapeutic thoracentesis can be performed. Unfortunately, for many patients, this
only offers short-term benefit and must be repeated with variable frequency, with
risk of procedure-related complications at each visit. Transjugular intrahepatic portosystemic
shunt (TIPS) placement is often performed in cirrhotic patients with refractory ascites
or hydrothorax, although ultimately may be unsuccessful for a minority of patients.[7] While liver transplantation remains the only definitive treatment, surgical pleurodesis,
diaphragmatic repair, and pleuroperitoneal shunt placement have also been described
in the management of hepatic hydrothorax.[6]
[7]
[8]
[9]
[10]
For patients with medically refractory pleural effusion unrelated to cirrhosis, thoracentesis,
surgical pleurodesis, and pleurovenous shunt placement remain in the treatment paradigm.
If life expectancy is limited, consideration should be given to placement of a tunneled,
valved pleural drainage catheter (PleurX, BD, Chicago, IL) for noncirrhotic patients
requiring frequent thoracentesis. These tunneled catheters provide the capability
to perform intermittent drainage, and function well for weeks to months following
placement.[11]
[12]
[13] Occasionally, placement can lead to spontaneous pleurodesis for some patients.[11]
[12]
[13] If the anticipated duration of therapy is greater than 6 months, indwelling tunneled
pleural catheters are less favored.[11]
[12]
[13] For the small subset of patients with good overall prognosis, but who are poor surgical
candidates, have failed or are not being considered for pleurodesis and/or TIPS placement,
or who are unable to maintain visits for frequent thoracenteses, pleurovenous Denver
shunt placement can be considered for palliation.
Potential candidates for pleurovenous shunt placement first undergo formal clinical
evaluation in the ambulatory setting. Absolute contraindications to the procedure
include uncorrectable bleeding diathesis, sepsis, bacteremia, end-stage renal disease
requiring dialysis, and active pulmonary or pleural infection.[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23] Severe chronic kidney disease, central venous stenoses, congestive heart failure,
and septated pleural effusions are relative contraindications to shunt placement.[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
Shunt Placement
Appropriately selected patients are brought to the fluoroscopy suite and positioned
in a 30-degree anterior oblique position corresponding to the symptomatic side (usually
right). Preprocedural antibiotic prophylaxis is routinely administered. The procedure
is commonly performed under moderate sedation. The skin is prepped and draped from
the neck to below the costal margin. Initial ultrasound images are obtained to delineate
a safe window for percutaneous access of the pleural effusion, ideally along the mid-axillary
line directed slightly caudally and posteriorly. Percutaneous pleural access is established
with a 5-Fr needle-mounted catheter, and a stiff 0.035-inch working wire is advanced
into the pleural cavity. The tract is then sequentially dilated over the wire to accept
a 16-Fr peel-away sheath. A 3-cm incision is then made at the costal margin cephalad
to the pleurotomy site and a subcutaneous pocket is created to receive the pump chamber.
It is important that the chamber be well-seated over the ribs to provide an appropriate
backstop for pumping. The pleural limb is tunneled to the pleurotomy site and the
catheter is placed with some redundancy positioned in the posterobasal hemithorax.
Using ultrasound guidance, the ipsilateral internal jugular vein is then accessed
and the tract sequentially dilated over a wire to a 16-Fr peel-away sheath. The venous
limb of the catheter is then tunneled subcutaneously from the pocket to the venotomy
site and cut to length for final position with the tip at the superior cavoatrial
junction. A second incision below the clavicle may be required to complete the tunneling
process. After priming the system by repeatedly compressing the pump chamber, the
venous limb is placed, and the incisions are closed ([Fig. 1]).
Fig. 1 Single fluoroscopic image following right-sided pleurovenous Denver shunt placement
demonstrating the pleural access site at the 8th intercostal space, and the pleural
limb of the catheter terminating in the basal hemithorax (arrowheads). The subcutaneous
pump is seen just cephalad to the pleural access site (asterisk), and the venous limb
of the catheter can be followed to the superior cavoatrial junction (arrow). A thin
radiopaque stripe is present along the entirety of the catheter; no contrast was injected.
A massive right pleural effusion is present, compressing the right lung.
Shunt Evaluation
It is common to see patients in consultation for shunt evaluation after placement
([Fig. 2]). Poor shunt function is suggested by persistent or worsening symptomatic pleural
effusion. To be evaluated fluoroscopically, the shunt system can safely be accessed
via cannulating the pump or either catheter limb using a non-coring needle (e.g.,
Huber needle), which should not result in any damage to the system that would inhibit
further use. After accessing the shunt, dilute contrast material is injected by hand
under digital subtraction angiography. A patent venous limb should opacify readily
with contrast and demonstrate rapid emptying into the right atrium ([Fig. 3]). The entire venous limb should be evaluated, although, when present, filling defects
may be seen in the dependent portion of the shunt adjacent to the pump. Any reflux
of contrast following injection indicates a malfunctioning unidirectional valve. The
pleural limb of the shunt system can be evaluated similarly by accessing the catheter
just caudal to the pump and injecting while manual pressure is held over the venous
limb.
Fig. 2 Frontal chest radiograph of a 44-year-old man with refractory right-sided hepatic
hydrothorax with near-total white out of the right hemithorax (left). Six months following
right-sided pleurovenous Denver shunt placement, frontal chest radiograph demonstrates
significant improvement in the right pleural effusion and right lung expansion (right).
No shunt revision or replacement occurred in the interval.
Fig. 3 Single digital subtraction angiography image during pleurovenous Denver shunt evaluation
in a 51-year-old cirrhotic patient with right hepatic hydrothorax and persistent shortness
of breath. Contrast injection demonstrates uniform opacification of the venous limb
and rapid emptying into the right atrium (arrow) consistent with a patent shunt. The
patient was counseled on pumping instructions.
Outcomes and Complications
Outcomes and Complications
The safety and efficacy of pleurovenous shunting for refractory effusion is poorly
studied, with few reports describing favorable technical and clinical success of the
procedure.[17]
[18]
[19]
[20] In the authors' experience, inadequate drainage of pleural fluid may be encountered
following shunt placement. The Denver shunt system is designed to allow flow through
the unidirectional valves with pressure gradients as little as 3 to 5 cm H2O. When managing ascites with a peritoneovenous shunt, generation of negative intrathoracic
pressure during inspiration can be sufficient to facilitate flow of ascites into the
central venous circulation while supine. Following pleurovenous shunt placement, the
pressure differential is not as sufficient, as the entire system is implanted within
the thoracic cavity. Due to this, patients are almost entirely dependent on the pumping
mechanism. It is imperative that patients are counseled adequately both pre- and postprocedure
regarding the importance of shunt pumping, and together with their caregivers should
be shown how to operate the pump after it has been placed. Marking the skin overlying
the pump chamber may be beneficial for some patients. The shunt system should be pumped
several times per day while lying supine. Each pump may physically move 1 to 2 cc
through the chamber and catheter. It is feasible that some patients may experience
buildup of pleural fluid more rapidly than can be drained via the shunt system despite
adequate pumping.
Consideration should be carefully given to size and location of the subcutaneous pocket
created for the pump chamber. The chamber must be well situated over the ribs and
stable enough to accommodate repeated pumping ([Fig. 4]). Attention should be paid to not create too large a pocket, as it is feasible for
the pump to flip subcutaneously ([Fig. 5]). In this setting, it is possible for the pump to remain functional by compression
against the ribs, but unfortunately is no longer easily accessible percutaneously
for evaluation without first repositioning the system.
Fig. 4 Axial and sagittal CT images of different patients demonstrating the Denver shunt
pump chamber. On the sagittal image, the one-way “check” valve is evident (arrow),
which prevents reflux of material from the venous limb while the chamber refills between
sequential pumps.
Fig. 5 Axial CT image of a 56-year-old man with cirrhosis and right hepatic hydrothorax
who previously underwent right-sided pleurovenous Denver shunt placement. The shunt
pump can be seen flipped 180 degrees within the subcutaneous pocket (arrow). This
patient was still able to operate the pump with clinical benefit.
Peritoneovenous Denver shunt placement has been reportedly associated with the development
of postprocedure consumptive coagulopathy and circulating fibrin split products.[21]
[22]
[23] Though no clear data exist on the rate of adverse events associated with pleurovenous
Denver shunt placement, baseline assessment of renal function should be performed
at the time of initial clinical evaluation, and coagulation parameters should be obtained
in the preprocedural setting.[17]
[18]
[19]
[20] Postprocedure care requires observation for the development of fluid overload and
post-shunt coagulopathy. Repeat laboratory evaluation, to include a disseminated intravascular
coagulation (DIC) profile, can be performed as needed.
Additional potential complications related to pleural access during the procedure
include pneumothorax, hemothorax, and leakage of pleural fluid via the skin incision
with or without wound dehiscence.[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23] Less common complications associated with the indwelling shunt system include catheter
malposition, catheter obstruction, and infection.[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
Conclusion
Pleurovenous Denver shunt placement may be considered as part of the treatment paradigm
for patients with medically refractory, nonmalignant pleural effusion who have failed
or are not being considered for surgical management, and for whom frequent thoracentesis
is not tolerated or provides inadequate palliation. Complications include inadequate
drainage, catheter or pump malposition, and shunt malfunction or obstruction. There
is a potential association with the development of DIC postprocedure; however, more
data are needed to assess the safety profile and efficacy of pleurovenous shunt placement
in this patient population.
