Volume 55, Issue 2 , Pages 395-398, February 2010
Radiographic Features of Malpositioning of a Hemodialysis Catheter in the Azygos Vein
Article Outline
Index Words: Azygos vein, hemodialysis, catheter
Introduction
Percutaneous image-guided insertion of a tunneled hemodialysis catheter is a common procedure practiced by interventional nephrologists and radiologists. Among the myriads of reasons for catheter dysfunction presenting as poor flow during dialysis, inadvertent placement of the catheter into the azygos vein is a known, but rare, cause. This malpositioning can be difficult to detect during catheter insertion, as well as on chest radiography, given the subtle clinical and imaging findings. Familiarity with the radiographic features, therefore, is crucial for detection. We hereby illustrate the radiographic features of this malposition.
Case Report
Clinical History and Initial Laboratory Data
A 39-year-old man with end-stage renal failure secondary to diabetic nephropathy presented with persistently poor flow rate in his tunneled hemodialysis catheter (Hemostar; Bard Access Systems, Salt Lake City, UT). The catheter was inserted 2 months prior when he presented with acute pulmonary edema requiring initiation of hemodialysis therapy. The catheter was placed without difficulty through a right internal jugular vein puncture under sonographic guidance and over a guidewire using real-time fluoroscopy.
Imaging Studies
Fluoroscopic imaging on presentation showed a gentle kink at the right tracheobronchial angle with medial deviation of the catheter tip across the midline spinous processes (Fig 1A). These findings also were seen on the admission chest radiograph (Fig 1B; correct placement is shown for comparison in Fig 1C). Injection of contrast through the venous port of the catheter confirmed the malposition of the hemodialysis catheter in the azygos vein (Fig 2A).
Figure 1.
(A) Spot fluoroscopic image shows a gentle kink (black arrow) in the hemodialysis catheter that occurs directly adjacent to the right tracheobronchial angle (black line), which is a constant anatomic landmark that demarcates the path of the trachea and right main bronchus. The tracheobronchial angle marks exactly where the azygos vein opens into the superior vena cava. The presence of a kink at this location indicates that the hemodialysis catheter has entered the azygos vein. Because of the medial course of the azygos vein, the tip of the hemodialysis catheter can be seen crossing the midline spinous processes (white arrow). (B) Frontal chest radiograph of the patient with the hemodialysis catheter within the azygos vein. The mentioned features seen on spot fluoroscopy can be identified. (C) Chest radiograph of another patient with correct hemodialysis catheter placement with the tip in the right atrium.
Figure 2.
(A) Digital subtraction angiogram, obtained by injecting contrast into the venous port, confirms catheter placement in the azygos vein (white arrow). The kink in the catheter is at the ostium of the azygos vein, where it drains into the superior vena cava (black arrow). (B) Spot fluoroscopic image shows the hemodialysis catheter after being redeployed within the right atrium.
Diagnosis
Malpositioning of the hemodialysis catheter in the azygos vein.
Clinical Follow-up
The indwelling hemodialysis catheter subsequently was removed over a guidewire, and a new catheter was inserted and positioned with tip placement in the right atrium (Fig 2B). Subsequent dialysis sessions were successful, with no further flow-related issues.
Discussion
Inadvertent placement of a hemodialysis catheter into the azygos vein is rare.1, 2 Although intentional placement of a catheter into the azygos vein now is a recognized alternative in patients with severe venous occlusion,3 the azygos vein generally is believed to be less preferred because of its relatively small vascular caliber and direction of blood flow.4 Furthermore, placement of a hemodialysis catheter into the azygos vein runs the risk of venous perforation with mediastinal hemorrhage, venous thrombosis, and complete vein occlusion.5 Risk factors for malpositioning into the azygos vein include left internal jugular venous access, use of catheters with long venous tips, and catheter insertion in a patient with fluid overload.1 The latter is related to increased right atrial pressure and its effect on the ostium of the azygos vein. The size of the ostium of the azygos vein is ∼6-8 mm under normal physiologic conditions, but significantly increases in the presence of increased right atrial pressure (eg, fluid overload).6 This increase in ostial size increases the chance of inadvertent cannulation during hemodialysis catheter insertion.
Guidewire or catheter kinking at the right tracheobronchial angle is an important radiographic telltale sign, but can be subtle (Figs 1A, 1B, and 3A). The tracheobronchial angle, the “corner” at which the trachea gives off the right main bronchus, is a constant anatomic landmark on frontal radiography and marks the exact location where the azygos vein arches over the right main bronchus to enter the superior vena cava. Inadvertent cannulation of the azygos arch will necessitate passage of the guidewire or hemodialysis catheter into the azygos arch at exactly this point. Additionally, the azygos vein takes a medial course toward and across the midline as it progresses caudally. This results in medial deviation of the catheter or wire tip across the midline spinous process if placed in the azygos vein.
Figure 3.
Spot fluoroscopic images of a companion case. The guidewire was inserted after a left internal jugular venous puncture. (A) Guidewire cannulation of the azygos vein shows the characteristic kink (black arrow) at the constant landmark location of the right tracheobronchial angle, similar to Fig 1A. Medial deviation of the guidewire also is seen as it crosses the midline spinous process while following the path of the azygos vein (white arrow). (B) Successful guidewire manipulation into the inferior vena cava shows the absence of a kink at the tracheobronchial angle and the straight vertical path of the guidewire (white arrow). It should be noted that in both instances, the guidewire could be advanced below the level of the diaphragm, showing that this common practice to confirm venous placement cannot be used to exclude azygos vein cannulation.
Malpositioning of a hemodialysis catheter into the azygos vein can be difficult to detect during catheter insertion because venograms are not routinely obtained. Many operators routinely advance the guidewire below the level of the diaphragm (into the inferior vena cava) to confirm good venous access before hemodialysis catheter deployment. This usually is followed by rigorous hand aspiration and flushing of venous blood to confirm adequate placement. However, neither of these maneuvers can be used to exclude azygos vein cannulation. As shown in our companion case (Fig 3), the azygos vein, like the inferior vena cava, runs a course that extends below the level of the diaphragm, and the operator easily can be misled. Furthermore, venous blood also can be aspirated readily from the azygos vein, leading to the clinical impression of adequate catheter tip placement. Therefore, without recognition of the radiologic signs, the malposition easily can be missed unless additional venographic assessment or cross-sectional imaging is performed. A high index of suspicion is needed, and detection of malpositioning of a hemodialysis catheter into the azygos vein hinges on the understanding of key anatomic landmarks and recognition of these radiographic features. Their presence should provoke further assessment using lateral projection radiography or contrast venography.
Acknowledgements
Support: None.
Financial Disclosure: None.
References
- Azygos arch cannulation by central venous catheters: radiographic detection of malposition and subsequent complications. J Thorac Imaging. 1997;12:64–69
- . Quiz page (Right internal thoracic cannulation by CVC for hemodialysis therapy). Am J Kidney Dis. 2008;51(5):A42–A44
- . Azygos tip placement for hemodialysis catheters in patients with superior vena cava occlusion. Cardiovasc Intervent Radiol. 2006;29(1):143–146
- . Azygos catheter placement as a cause of failure of dialysis. Clin Radiol. 1993;48(5):329–331
- . Azygos arch cannulation by central venous catheters for hemodialysis. J Vasc Access. 2006;7:43–45
- . Radiologic appearance of the azygos vein in cardiovascular disease. Circulation. 1973;47:628–634
Originally published online as doi:10.1053/j.ajkd.2009.06.041 on September 27, 2009.
PII: S0272-6386(09)01030-0
doi:10.1053/j.ajkd.2009.06.041
© 2010 National Kidney Foundation, Inc. Published by Elsevier Inc All rights reserved.
Volume 55, Issue 2 , Pages 395-398, February 2010
