Approach to the Swollen Arm With Chronic Dialysis Access

Transcription

1 PICTORIAL ESSAY Approach to the Swollen Arm With Chronic Dialysis Access It s Not Just Deep Vein Thrombosis Shilpa N. Reddy, MD, Meghan C. Boros, MD, Mindy M. Horrow, MD The purposes of this pictorial essay are as follows: (1) Review a systematic approach to using sonography in the initial evaluation of patients with acute arm swelling and permanent dialysis access. (2) Identify normal grayscale and Doppler findings in arteriovenous fistulas and grafts. (3) Discuss a spectrum of vascular differential diagnoses for arm swelling in this setting, including stenosis of the access, draining vein complications, thrombosis, steal syndrome, and aneurysms, as well as several nonvascular causes. (4) Recognize findings that warrant further imaging evaluation or intervention. Key Words access; arm swelling; fistula; graft; hemodialysis; sonography; vascular ultrasound Received November 24, 2014, from the Department of Radiology, Einstein Medical Center, Philadelphia, Pennsylvania USA. Revision requested December 9, Revised manuscript accepted for publication December 16, Material in this article was presented as an educational exhibit at both the 2014 American Roentgen Ray Society Annual Meeting; May 4 9, 2014; San Diego, California; and the 2014 Radiological Society of North America Scientific Assembly and Annual Meeting; November 30 December 5, 2014; Chicago, Illinois. Address correspondence to Mindy M. Horrow, MD, Department of Radiology, Einstein Medical Center, 5501 Old York Rd, Philadelphia, PA USA. horrowm@einstein.edu, mhorrow@ gmail.com Abbreviations PSV, peak systolic velocity doi: /ultra Venous Doppler sonography is frequently the initial study requested to evaluate acute arm swelling in patients with hemodialysis arteriovenous fistulas and grafts. Although it is important to exclude deep vein thrombosis in these patients, imagers must consider a wide spectrum of other vascular and nonvascular causes of acute arm swelling. Many of these diagnoses can be appreciated or suggested sonographically, whereas others require further imaging evaluation or intervention. This pictorial essay is based on a computerized search and review of all cases of acute arm swelling in patients with permanent dialysis access at our hospital over an 8-year period. Venous Causes of Acute Arm Swelling Approach to Evaluating Deep and Superficial Veins A routine examination of the upper extremity should include both deep and superficial veins and limited spectral Doppler imaging of the contralateral subclavian vein for comparison (Figure 1). Nine-megahertz linear transducers are typically adequate, although phased array transducers with small footprints are helpful to evaluate the subclavian vein, brachiocephalic vein, and superior vena cava via a supraclavicular approach. A lower-frequency curved transducer may be necessary in obese patients or those with substantial 2015 by the American Institute of Ultrasound in Medicine

2 swelling. All deep and superficial veins should be evaluated by grayscale imaging with and without compression, color Doppler imaging, and spectral Doppler imaging. All venous waveforms should have normal respiratory variability. A venous waveform without respiratory variability should raise concern for thrombosis more centrally. In these cases, comparison of the venous waveform in the contralateral arm can be helpful for determining the central extent of the thrombus. For example, if there is loss of normal respiratory variability in waveforms of the contralateral subclavian vein, superior vena cava thrombosis should be suspected rather than brachiocephalic thrombosis. Any ipsilateral central venous catheter or cardiac device should also be assessed for an adherent clot or fibrin sheath, as any indwelling foreign body can serve as a nidus for thrombosis (Figure 2). Venous Thrombosis and Stenosis Incomplete compressibility of a vein on transverse grayscale imaging is the most sensitive finding for venous thrombosis (Figure 3). If a thrombus is present, the cranial extent of the thrombus should be documented. Particularly when a thrombus is seen in a superficial vein, it is important to determine whether the clot progresses into deep veins (Figure 4). Although the benefits of treating deep vein thrombosis are well known, management of superficial vein thrombosis is not well established, particularly in patients with an ipsilateral arteriovenous fistula or graft. Studies have reported that up to 10% of patients with superficial vein thrombosis may develop deep vein thrombosis, pulmonary embolism, or progression of superficial vein thrombus in 3 months. 1 Therefore, the decision to anticoagulate patients is generally considered on a case-bycase basis. Deep and central vein stenosis is also an important cause of arm swelling because if left untreated, it can result in graft dysfunction and failure. Areas of luminal narrowing on grayscale imaging should be further evaluated with color and spectral Doppler imaging. Both a color bruit and aliasing can be seen in areas of substantial stenosis (Figure 5). Figure 2. Thrombus along an indwelling catheter. Grayscale sagittal image of the right internal jugular vein in a patient with right arm swelling and a right upper extremity arteriovenous fistula shows an echogenic thrombus (arrow) extending along an indwelling catheter. Figure 1. Upper extremity deep and superficial veins. Schematic shows major deep and superficial upper extremity veins that are evaluated for deep vein thrombosis in the initial workup of arm swelling. Figure 3. Deep vein thrombosis. Transverse grayscale images of the axillary vein with and without compression show incompressibility of the vein, which is completely filled with a thrombus (arrows). 1902

3 Labropoulos et al 2 reported a stenotic-to-prestenotic peak vein velocity ratio of greater than 2.5 to be a good predictor of hemodynamically significant stenosis. 2 Although sonography is limited in its sensitivity to primarily visualize central vein stenosis, loss of normal respiratory variability or flow that is decreasing over time can infer stenosis centrally. Draining Veins Large draining veins can also result in substantial arm swelling and may contribute to up to 40% of arteriovenous fistula failures. 3 It is hypothesized that increased venous pressures promote filling of multiple collateral perforator veins, which can cause arm swelling and steal blood away from the fistula or graft. Central vein stenosis is often the inciting event; therefore, management usually involves treating the central vein stenosis in addition to coil embolization of the draining veins. Draining veins occur more frequently in patients with an arteriovenous fistula than those with an arteriovenous graft. 3 On sonography, draining veins appear as a tangle of dilated veins near the access (Figure 6). These dilated draining veins may result in insufficient flow in the dialysis access, and their embolization may improve flow, allowing continued use of the fistula for dialysis. Causes of Acute Arm Swelling Intrinsic to an Arteriovenous Fistula or Graft Approach to Evaluating the Arteriovenous Graft or Fistula After a complete venous examination, especially if results are negative for thrombosis, other dialysis access related causes of swelling should be considered. Such an evaluation requires an understanding of the different types of dialysis access and their normal grayscale and Doppler appearances. An arteriovenous graft uses synthetic material to create a conduit between an artery and vein. The arteriovenous graft is named after the inflow artery and outflow vein (eg, brachial-cephalic arteriovenous graft). Thus, an arteriovenous graft has 2 connections, the inflow artery graft anastomosis as well as the graft outflow vein anasto- Figure 4. Superficial vein thrombosis progressing into deep vein thrombosis. A, Transverse grayscale images of the cephalic vein show a hypoechoic thrombus within the vein, which also fails to compress (arrows). B, Initial evaluation of the brachial veins on this transverse color Doppler image shows paired patent brachial veins (arrows). C, Sonography performed 10 days later for worsening arm swelling shows a hypoechoic thrombus occluding one of the brachial veins on this transverse color Doppler image (arrow), indicating propagation of the thrombus into deep veins. 1903

4 mosis (Figure 7A). On grayscale sonography, the graft material appears as 2 parallel echogenic lines (Figure 8). Imaging of the anastomosis will show the graft material sewn into the native artery or vein. Grayscale, color Doppler, and spectral Doppler sonography of the inflow artery, artery-graft anastomosis, graft conduit, graft-vein anastomosis, and outflow vein should be performed for thorough evaluation of the arteriovenous graft. The normal waveform in the inflow artery is monophasic with low resistance, typically with substantial turbulence. The peak systolic velocity (PSV) in the inflow artery is usually greater than 150 cm/s (Figure 9). Although spectral Doppler sonography of arteries cranial to the arteriovenous fistula or graft will show monophasic low-resistance arterial flow, arteries caudal to the access should show a high-resistance triphasic waveform typical of a normal resting extremity artery (Figure 10). The normal range of PSV within the artificial conduit of an arteriovenous graft is 100 to 400 cm/s. 4 Spectral Doppler imaging of the outflow vein should be monophasic and turbulent with a high-velocity arterial-type waveform but may not have the brisk arterial upstroke seen in the inflow artery (Figure 11). The PSV at the artery-graft and graft-vein anastomoses may be somewhat high but should be no more than 2 times elevated. 4 To create an arteriovenous fistula, the native vein is mobilized and anastomosed to a native artery so that no foreign material is involved. The fistula is named for the inflow artery and vein that creates the fistula. An arteriovenous fistula will only have 1 anastomosis (Figure 7B). Sonography of the inflow artery, arteriovenous anastomosis, and outflow vein should be performed for thorough evaluation of the entire arteriovenous fistula. Similar to the inflow artery of an arteriovenous graft, spectral Doppler imaging of the inflow artery in an arteriovenous fistula Figure 5. Central vein stenosis in a patient with a brachial-cephalic arteriovenous fistula. A, Color Doppler image of the suspected area of stenosis shows aliasing and turbulent flow (arrow), confirming stenosis. B, Spectral Doppler image of the stenotic segment shows an elevated PSV. EDV indicates end-diastolic velocity. C, Preintervention angiogram shows severe stenosis in the cephalic vein (arrow) at the subclavian vein junction, corresponding to that seen on sonography. 1904

5 should also be monophasic with low resistance and substantial turbulence (Figure 9). The PSV at the arteriovenous anastomosis should be noted and compared to the PSV in the inflow artery. Generally, the PSV at the anastomosis may be focally high but should be no more than 3 times that of the inflow artery. 4 Spectral Doppler imaging within the outflow vein is typically monophasic and arterialized, similar to that seen in an outflow vein of an arterio - venous graft (Figure 11). Figure 6. Draining veins in a patient with an arteriovenous fistula and arm swelling. A, Color Doppler image shows multiple engorged collateral vessels (arrow) adjacent to an arteriovenous fistula (not shown). B, Corresponding pretreatment angiogram with a catheter superselecting a dominant draining vein shows filling of numerous collateral veins along the forearm. Arteriovenous Fistula or Graft Thrombosis Thrombosis of an arteriovenous fistula or graft is one of the most common causes of access dysfunction and can result in substantial acute arm swelling. On physical examination, the patient will have a very weak or absent pulse over the access site. On grayscale imaging, a hypoechoic thrombus will fill the graft or fistula. It is helpful to document the extent of the thrombus along the inflow artery and along the outflow vein or fistula (Figure 12). In addition, the waveforms in the inflow artery cranial to the thrombosed arteriovenous graft or fistula will revert to a high-resistance triphasic pattern (Figure 12C). With subacute or chronic thrombosis, the clot will retract and become more echogenic, and the dialysis access will decrease in size (Figure 13). The risk factors for graft/fistula thrombosis are generally turbulent and/or low flow in the access and include stenoses in the arterial inflow, venous outflow, central veins, and even within the graft or fistula. 5 Other systemic risk factors for access thrombosis include a hypercoagulable state and hypotension. 5 Figure 7. Arteriovenous graft and arteriovenous fistula. A, Schematic of an arteriovenous graft shows artificial graft material creating a conduit between the inflow artery and outflow vein. Note that this material creates an artery-graft anastomosis as well as a graft-vein anastomosis (broken arrows). B, Schematic of an arteriovenous fistula shows mobilization of a superficial vein to the inflow artery to create the fistula. The 3 main parts of an arteriovenous fistula are labeled the inflow artery, arteriovenous anastomosis (broken arrow), and fistula. 1905

6 Stenosis Within an Arteriovenous Fistula or Graft Any focal areas of increased flow in an arteriovenous fistula or graft should raise concern for focal stenosis, and the velocities proximal and distal to the abnormal area should be documented. The most common locations for stenosis in an arteriovenous graft are the graft-vein anastomosis, followed by the outflow vein, graft conduit, and artery-graft anastomosis. 4 In an arteriovenous graft, a 2- to 2.9-times focal elevation of the PSV has been associated with at least 50% stenosis. 6 Focal elevation of the PSV greater than 3 times typically indicates greater than 75% luminal narrowing. 6 The most common locations for stenosis in an arteriovenous fistula are the arteriovenous anastomosis, the outflow vein, and, rarely, the inflow artery. 7 In an arteriovenous fistula, the PSV at the arteriovenous anastomosis may be elevated, but a PSV greater than 3 times that of the inflow artery indicates hemodynamically significant stenosis. 4 Although these patients will typically require diagnostic angiography and venography, identifying stenoses on sonography can still be helpful as a guide to the vascular procedures, particularly in providing physiologic information regarding the stenosis. Steal Syndrome Steal syndrome is a relatively rare but important complication occurring in up to 6% of patients with an arteriovenous fistula or graft. 8 Patients with steal syndrome can present with substantial pain and swelling in the extremity and often describe pain worsening with exercise or during dialysis. The pathophysiologic mechanism of steal syndrome involves a shift in hemodynamics that occurs when an arteriovenous fistula or graft is created. Blood in the inflow artery has 2 options: it can flow into the low-resistance pathway through the artificially created fistula/graft, or it can take the high-resistance pathway to arteries distal to the fistula. In a normally functioning fistula or graft, dilatation of arteries cranial and caudal to the access allow for an overall increase in blood flow to the extremity and, as a result, relative preservation of blood flow to the caudal high-resistance arteries of the upper extremity. Steal syndrome occurs when the compensatory mechanism fails. For example, inflow arterial stenosis and advanced peripheral vascular disease can prevent a sufficient increase in blood flow necessary to compensate for hemodynamic changes related to the arteriovenous graft/fistula. A large arteriovenous fistula that creates an extremely low-resistance pathway for blood flow can also result in steal syndrome. Diagnosing steal syndrome on sonography can be challenging and often requires a high clinical suspicion before the examination. Evaluation of the arteries caudal to the access will show decreased arterial blood flow and bidirectional flow. 8 Compression of the access should result in a substantial increase in blood flow to these peripheral arteries with normalization of waveforms (Figure 14). Figure 9. Normal inflow artery waveform. Spectral Doppler image of the inflow artery of an arteriovenous graft or fistula shows a normal monophasic low-resistance arterial waveform with moderate turbulence. Figure 8. Normal arteriovenous graft conduit on sonography. Sagittal grayscale image of an arteriovenous graft in the proximal arm shows the graft material, which appears as 2 parallel echogenic lines (arrows). Figure 10. Normal arterial waveform caudal to an arteriovenous graft or fistula. Spectral Doppler image of the artery caudal to the access shows a high-resistance triphasic waveform. Figure 11. Normal waveform in an outflow vein or fistula. Spectral Doppler image of the outflow vein in an arteriovenous graft or within a fistula typically shows a monophasic and turbulent arterial-type waveform. 1906

7 3410jum copy_layout 1 9/21/15 10:51 AM Page 1907 Reddy et al Approach to the Swollen Arm With Chronic Dialysis Access Figure 12. Acute thrombosis in an arteriovenous graft in a patient with acute arm swelling. A, Sagittal grayscale image shows a hypoechoic thrombus filling the arteriovenous graft. B, Sagittal color Doppler image confirms near-complete thrombosis. C, Spectral Doppler image of the inflow artery reverts to a high-resistance triphasic pattern. Figure 13. Chronic thrombosis in an arteriovenous fistula. Sagittal grayscale image from a patient with a failed arteriovenous fistula shows an organizing thrombus (arrow) filling the fistula. The lumen of the fistula is beginning to contract around the thrombus. Figure 14. Steal syndrome. Spectral Doppler image of the left radial artery distal to an arteriovenous fistula (AVF) shows trace arterial flow (left of the vertical yellow line). After compression of the arteriovenous fistula, flow in the radial artery improved substantially, with an increased PSV and a waveform with a brisk arterial upstroke. The patient s symptoms also improved after compression of the fistula. 1907

8 Compression of the access site may ameliorate the limb pain. Identifying arterial inflow stenosis, determining whether the arteriovenous fistula has abnormally high flow (or flow that has been increasing over time), and assessing symptom relief in response to compression of the graft or fistula are all very helpful for surgical treatment planning. Treatment options for steal syndrome include repairing the arterial stenosis if present, ligating or banding the access, or surgically creating bypass vessels to create collateral vessels to the distal extremity. 9 Pseudoaneurysms and Aneurysms Pseudoaneurysms occur in 2% to 10% of patients with arteriovenous grafts and can cause substantial arm swelling. 10 Pseudoaneurysms are presumably caused by tears in the graft material from multiple punctures. These tears result in bleeding from the access and formation of a periaccess hematoma. Persistent communication between a portion of the hematoma and the graft results in a pseudo aneurysm. Complications of pseudoaneurysms include graft failure, compartment syndrome, and infection. 11 Pseudo - aneurysms are easily visualized on sonography as a focal narrow-necked outpouching from the arteriovenous graft. Color Doppler imaging classically shows a yin-yang pattern of swirling flow within the perfused portion of the pseudoaneurysm (Figure 15). Spectral Doppler evaluation at the neck will show a to-and-fro pattern with highvelocity flow into the pseudoaneurysm in systole and continuous flow out in diastole. It is important to note that the pseudoaneurysm can be relatively small compared to the surrounding hematoma. Increasing the depth or using a lower-frequency transducer is essential to fully appreciate the extent of hematoma (Figure 16). Similar outpouchings along an arteriovenous fistula are considered true aneurysms and can be seen in up to 32% of patients with arteriovenous fistulas. 12 Aneurysms of arteriovenous fistulas are most commonly seen at the arteriovenous anastomosis or at weakened points in the wall of the vein related to repeated venipuncture. 7 Aneurysms place the fistula at risk for thrombosis, as they allow for areas of relative stasis or slow flow, which promotes formation of a thrombus. 7 Treatment traditionally involved surgical resection of the pseudoaneurysm or aneurysm and repair of the access. However, percutaneous placement of endovascular stent grafts is now commonly performed and has been proven effective. 7,11 Nonvascular Causes Finally, it is important to evaluate the soft tissues around the graft or fistula. Increasing transducer depth is essential to visualize deeper soft tissues, and curved transducers may be necessary in obese patients or those with substantial swelling and/or thigh grafts and fistulas. Nonvascular causes of arm swelling in this patient population encompass a wide range of entities, from fluid collections to arm masses (Figure 17). Depending on the acuity of blood products within a hematoma, hematomas can be difficult to distinguish from the surrounding soft tissues (Figure 18). Color Doppler imaging is helpful to show that a solidappearing region is actually an avascular hematoma. Fluid around an arteriovenous graft or arteriovenous fistula can indicate an acute infection. Occasionally, perifistula/graft abscesses can also be seen (Figure 19). Additionally, it is important to evaluate any old grafts that were left in a patient s arm, as these orphaned grafts can also become infected. Figure 15. Pseudoaneurysms in a patient with arm swelling and an arteriovenous graft. A, Color Doppler image over the area of arm swelling shows focal narrow-necked outpouching containing a yin-yang flow pattern. B, Corresponding preintervention angiogram shows multiple pseudoaneurysms along the arteriovenous graft (arrows). 1908

9 3410jum copy_layout 1 9/21/15 10:51 AM Page 1909 Reddy et al Approach to the Swollen Arm With Chronic Dialysis Access Figure 16. Pseudoaneurysm with hematoma in a patient with substantial arm swelling and an arteriovenous graft. A, Initial sonogram of the area of swelling obtained with a 9 2-MHz transducer shows a classic pseudoaneurysm (PA) arising from the arteriovenous graft (AVG). B, Increasing the depth (green oval) reveals a large, complex fluid collection, consistent with a hematoma. The initially imaged pseudoaneurysm is again noted (pa). C, Image obtained with a 5 2-MHz transducer shows multiple perigraft hematomas (arrows). The initially imaged pseudoaneurysm is again noted (PA). Figure 17. Mass causing arm swelling in a patient with an arteriovenous graft. Radiograph of the left arm with an arteriovenous graft shows an amorphous calcified mass (arrow) adjacent to the calcified graft (arrowheads), consistent with tumoral calcinosis. Figure 18. Intramuscular hematoma in a patient with arm swelling and an arteriovenous graft. A, Transverse grayscale image shows a large intramuscular hematoma adjacent to an arteriovenous graft that is nearly isoechoic with surrounding tissues (arrows). B, Color Doppler imaging is helpful in delineating the hematoma from the surrounding tissues (arrows). 1909

10 Conclusions A wide differential diagnosis must be considered in the evaluation of a patient with acute extremity swelling and permanent dialysis access. Sonography is an excellent modality for evaluation of common and uncommon causes of swelling in these patients. Consideration must be given to sonographic findings that may warrant additional imaging Figure 19. Perigraft infection and abscess in a patient with an arteriovenous graft presenting with arm swelling and fever. A, Transverse grayscale image shows fluid tracking along the arteriovenous graft (arrow). Note increased echogenicity of surrounding soft tissues, indicating surrounding inflammation. B, Color Doppler image of a focal fluid collection along the same arteriovenous graft (AVG) shows a focal abscess (arrow). evaluations or interventions. Although venous Doppler sonography may be ordered initially, many other important causes of arm swelling can be detected or suggested with careful sonographic examination, saving the patient time and often more expensive imaging studies and hopefully leading to prompt treatment that may help maintain the dialysis access. References 1. Decousus H, Quéré I, Presles E, et al. Superficial venous thrombosis and venous thromboembolism: a large, prospective epidemiologic study. Ann Intern Med 2010; 152: Labropoulos N, Borge M, Pierce K, Pappas PJ. Criteria for defining significant central vein stenosis with duplex ultrasound. J Vasc Surg 2007; 46: Nikam M, Popuri RK, Inaba A, et al. Arteriovenous fistula failure: is there a role for accessory draining vein embolization? J Vasc Access 2012; 13: Lockhart ME, Robbin ML. Hemodialysis access ultrasound. Ultrasound Q 2001; 17: Aruny JE, Lewis CA, Cardella JF, et al. Quality improvement guidelines for percutaneous management of the thrombosed or dysfunctional dialysis access. J Vasc Interv Radiol 2003; 14:S247 S Robbin ML, Oser RF, Allon M, et al. Hemodialysis access graft stenosis: US detection. Radiology 1998; 208: Van Tricht I, Wachter DD, Tordoir J, Verdonck P. Hemodynamics and complications encountered with arteriovenous fistulas and grafts as vascular access for hemodialysis: a review. Ann Biomed Eng 2005; 33: Malik J, Slavikova M, Maskova J. Dialysis access associated steal syndrome: the role of ultrasonography. J Nephrol 2003; 16: Mickley V. Steal syndrome: strategies to preserve vascular access and extremity. Nephrol Dial Transplant 2008; 23: Yasim A, Kabalci M, Eroglu E, Zencirci B. Complication of hemodialysis graft: anastomotic pseudoaneurysm a case report. Transplant Proc 2006; 38: Pandolfe LR, Malamis AP, Pierce K, Borge MA. Treatment of hemodialysis graft pseudoaneurysms with stent grafts: institutional experience and review of the literature. Semin Intervent Radiol 2009; 26: Salahi H, Fazelzadeh A, Mehdizadeh A, Razmkon A, Malek-Hosseini SA. Complications of arteriovenous fistula in dialysis patients. Transplant Proc 2006; 38: