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| Year : 2009 | Volume
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| Issue : 1 | Page : 35-43 |
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| Value of color doppler sonography in the assessment of hemodialysis access dysfunction |
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Khaled M Moghazy
Department of Radiology, King Faisal University, Dammam, Saudi Arabia
Click here for correspondence address and email
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 Abstract | | |
Arteriovenous fistula (AVF) is the most widely used means of vascular access for long-term hemodialysis (HD) and the complication rate related to AVF remains high. This study was conducted to determine the efficiency of Color Doppler sonography (CDS) in the assessment of AVF dysfunction. Over a period of 29 months, from January 2005 to May 2007, a total of 55 patients with AVF access dysfunction were included in the study. CDS were performed in the King Fahd Hospital of the University, Al-Khobar, Saudi Arabia. CDS allowed identification of 23 patients with stenotic segments and 16 others with venous thromboses. Six patients with venous aneurysm were encountered. Doppler flow rate assessment allowed differentiation of venous hypertension in two patients and steal syndrome in two other patients. Thus, the CDS findings carried a sensitivity rate of 96.4%. Two subclavian vein stenoses, causing reduced blood flow rate, were missed by CDS and later confirmed by angiography. Thirty-four patients underwent operative intervention. Our study suggests that CDS is an ideal noninvasive technique that allows the assessment of both anatomy and hemodynamics of an AVF. Keywords: Color Doppler, Hemodialysis, Access, Arteriovenous fistula
How to cite this article:
Moghazy KM. Value of color doppler sonography in the assessment of hemodialysis access dysfunction. Saudi J Kidney Dis Transpl 2009;20:35-43 |
How to cite this URL:
Moghazy KM. Value of color doppler sonography in the assessment of hemodialysis access dysfunction. Saudi J Kidney Dis Transpl [serial online] 2009 [cited 2022 Aug 15];20:35-43. Available from: https://www.sjkdt.org/text.asp?2009/20/1/35/44704 |
| Introduction | |  |
Arteriovenous fistula (AVF) is the most widely used means of vascular access for long-term hemodialysis (HD) in patients with end-stage renal disease. Satisfactory function of these artificial shunts is essential for adequate HD. [1] The complication rate related to permanent HD vascular access remains high and accessrelated problems are responsible for 50% of the hospitalization of dialysis patients. [1],[2]
Most of these complications are related to the thrice-weekly trauma to the graft inflicted by large core needles required for HD treatment. [2] Because potential sites for vascular access are limited, extending the life of an existing fistula or graft is of great benefit. Thus, early detection, localization, and characterization of lesions that compromise HD are extremely important because they may allow correction before failure of the access. [3]
Traditional methods of graft surveillance include: clinical examination, venous line pressure measurements during dialysis, urea or tracer recirculation measurement, duplex ultrasonography and angiography. [4] The frequency of occurrence of recurring access problems mandates a method of examination that is accurate, noninvasive, and can be repeated as often as needed to evaluate the morphology and function of the fistulas. Color Doppler sonography (CDS) has established itself in recent years as the procedure of first choice for the evaluation of HD access problems. [5],[6]
The morphological findings of AVF are far less important than their functional effects, which determine the selection of patients for intervention (fistula percutaneous angioplasty, fistula revision, creation of new fistula, closure of the fistula, collateral vein ligation, and aneurysm resection). CDS examination should always include both the morphology and the function of the fistula so that the clinical significance of fistula abnormalities can be appreciated. [7]
Duplex sonography and flow volume measurements have been used for graft surveillance for the prediction of graft failure. [8] According to reports in the literature, the mean flow rates range from 500 to 1000 mL/min. [9],[10],[11] An excessive fistula flow rate is often suspected when clinical problems such as cardiac failure, recurrent swelling of the access arm, or steal syndrome arise. Excessive fistula flow may, in some cases, necessitate surgical reduction of the anastomotic orifice or closure of the anastomosis with creation of a new fistula. In patients with proximal venous stenoses, fistula flow is an important factor in the development of venous congestive symptoms such as edema, pain, and atrophic skin changes. [7],[12]
This study was undertaken to determine the efficiency of CDS in assessment of AVF access dysfunction.
| Patients and Methods | | |
Over a period of 29 months, from January to May 2007, a total of 55 patients with AVF access dysfunction, who were referred to the radiology department from vascular clinic, at the King Fahd Hospital of the University, Saudi Arabia, were studied. The fistula had been in place for 2-14 months. Color Doppler and duplex ultrasonography was performed with 7.5 MHz linear array transducer. Criteria of patient selection with AVF malfunction were as follows:
- Inappropriately low arterial shunt flow and/or high venous pressure during HD.
- Difficulty in fistula cannulation necessitating several attempts for adequate blood flow.
- Reduced shunt flow by auscultation or palpation.
- Persistent discomfort in the fistula arm to the patient.
On the basis of CDS findings, normal AVF had walls with smooth contours in both longitudinal and transverse image planes and the lumen, including the region of anastomosis, had to be unobstructed and completely filled with color flow signals. The spectral Doppler showed the typical flow pattern of persistently high diastolic flow velocities in the feeding artery.
The following criteria were used for CDS diagnosis of AVF abnormalities: Fistula stenosis was a circumscribed constriction of the vessel lumen within the AVF vein or in the region of the CDS flow stream with turbulent high velocity systolic flow and low diastolic flow by spectral Doppler. Fistula thrombosis was an echogenic mass (thrombus) protruding into the vessel lumen, associated with partial or complete occlusion of the lumen. Fistula aneurysm was a circumscribed region of dilatation of the AVF lumen with distinct borders filled with CDF signals of low velocity.
Duplex US was performed as a study of the following areas of access: the feeding artery, arterial anastomosis, venous anastomosis, and venous outflow to the subclavian vein. Color flow Doppler US was performed of the entire HD access system, and waveforms were measured in any areas in which high velocity was suspected.
Thirty-Four patients underwent operative interventions after CDS examination. Detailed anatomical descriptions of the operative findings in all patients were obtained, and surgical findings were taken as the reference standard with which CDS results could be compared.
| Results | | |
Fifty-five upper extremities that were imaged by means of color Doppler sonography and duplex ultrasonography met the inclusion criteria for the study. There were 38 males (69%) and 17 females (31%), with a mean age of 45.2 years (range 22-63 years).
Indications for color duplex sonography included symptoms in 40 patients (72.3%) and inadequate flow for dialysis without local manifestations in 15 others (27.3%).
[Table 1] depicts the presenting manifestations in the study patients. Thirty-one patients (56.3%) had diffuse edema of the fistula limb including 18 patients (32.7%) with painless edema and 13 patients (23.6%) with painful edema. Severe agonizing pain in the hand without evident swelling was encountered in two patients (3.6%). Localized swelling in the arm was found in seven patients (12.7%); six were painless and one was tender [Table 1].
Venous outflow stenosis was the most common access malfunction in this study, seen in 25 patients (45.5%). Access thrombosis was the second most frequent cause of access malfunction detected in 16 patients (29.1%). There were six venous aneurysms (10.9%). One patient had cellulitis with small collection around the AVF [Table 2]. CDS was indeterminate in two patients (3.6%) because of incomplete visualization of the subclavian vein caused by artifact from overlying bone. Duplex examination revealed reduced flow rate in both patients and angiography confirmed the presence of subclavian vein stenosis.
Adequate flow rate (500 - 1500 mL/min) was detected by Doppler study in 13 patients (23.6%) while inadequate flow rate (< 500 mL/min) was found in 19 patients (34.6%). Increased flow rate was seen in seven patients (12.7%) and no flow through the AVF was detected in 16 patients (29.1 %) [Table 3].
[Table 4] shows the relation between the flow rate in the AVF in our patients and the pathological findings on color Doppler examination. Adequate flow rate was found in one patient with localized swelling due to infection at the site of puncture [Figure 1] and six patients with venous aneurysm [Figure 2]. The remaining six patients with adequate flow rate had mild venous stenosis of the proximal venous limb of the AVF; basilic vein in one patient [Figure 3], cephalic vein in two patients and subclavian vein stenosis in three patients [Figure 4]. Reduced flow rate in AVF dialysis accesses was noted in 18 patients with venous stenosis (32.7%) and one patient with distal thrombosis (1.8%). Patients with increased flow rate in the AVF had manifestations of peripheral ischemia [Figure 5] or venous hypertension [Figure 6] with painful edema. Additional Doppler findings were increased distal venous flow in patients with venous hypertension and decreased distal arterial flow in patients with peripheral ischemia.
Diffuse swelling of the upper limb with reduced flow rate was seen in 31 of the study patients (56.3%) due to severe stenosis [Figure 7] or complete venous thrombosis [Figure 8],[Figure 9],[Figure 10]. Upper limb swelling with over flow was found in five patients (9.1%) due to venous hypertension. Asymptomatic venous stenosis, with inadequate flow rate, was found in 11 patients (20%); the percentage of stenosis ranged from 30 to 60%. Stenosis with edematous upper limb was found in 14 patients (25.4%) with severity of stenosis ranging from 55 to 85%.
Surgery confirmed the CDS findings in 34 patients (61.7%). Compared with the anatomical findings at surgery, CDS had 100% sensitivity for AVF stenosis detection. Twelve (21.7%) of the major complications necessitated either fistula ligation (3 patients) or revision (9 patients). Thrombectomy was performed in 11 pa-tients (20%). A new AVF was created in six patients (10.9%). True aneurysmal dilatation did not require treatment but false aneurysm was managed surgically by resection in four patients (7.3%). Placement of an AVF created a steal syndrome in two patients, both of whom were diabetic; relief of disabling symptoms required fistula revision in one patient and AVF ligation in another patient. Peripheral venous hypertension with diffuse painful edema and stiffness limited to the hand and distal forearm was seen in five patients (9.1%); one patient responded to conservative therapy, and two patients were successfully treated by ligating the distal cephalic vein, while access revision was done in two other patients [Table 5].
| Discussion | | |
Standard techniques for assessing AVF anatomy and flow have major limitations. Clinical assessment, indicator-dilution techniques, and pulsed-wave Doppler without ultrasonographic imaging do not provide sufficient anatomical information. Angiography is an invasive technique, so it cannot be frequently repeated and can be associated with discomfort and potential fistula injury. [13] Furthermore, in patients with total or near complete fistula occlusion due to thrombosis, puncture of the vessel may be difficult or impossible. The length of a thrombosed segment is not easy to assess on angiography, and sometimes non-thrombotic stenoses cannot be differentiated angiographically from partial AVF thrombosis; this differentiation, however, is important for decisions on fistula repair. In addition, aneurysms filled with thrombotic material can be missed. [1]
The diagnostic criteria on Color Doppler and duplex ultrasonography for stenosis are visible narrowing of the lumen, increased velocity of flow greater than 100% compared with that in adjacent normal segment or a region of focal aliasing in color Doppler study. [14],[15] In our study, venous outflow stenosis accounted for 45.5% of access malfunctions, while access thrombosis was the second frequent access complication (29.1%). This percentage is not consistent with that reported in other screening programs, in which a lower percentage of stenoses were found in the groups studied. In the study of Culp K et al, [16] access thrombosis was the predominant complication reaching 70% and stenosis was noted in only 20% of the patients. This may be explained by the value of Doppler study in assessing the flow rate in our study, which can diagnose any reduction in the flow rate associated with access stenosis. Asymptomatic venous stenosis with inadequate flow rate, was found in 11 patients (20%) with the percentage of stenosis ranging from 30 to 60%, while stenoses with edematous upper limb was found in 14 patients (25.4%) with significant stenosis ranging from 55 to 85%. Schwab SJ et al, [17] found hemodynamically significant stenosis greater than 50% in 86% of patients with low AVF flow rate. The location of the stenotic segment differs from one study to another. In our study, nine stenotic segments were found at the region of AVF, six in the venous limb distally and ten stenotic segments in the subclavian vein. In another study, [18] CDS showed a fistula stenosis without thrombosis in the region of the AVF in 10 patients or further down in the venous vessel in eight patients. In the study of Sullivan KL et al, [19] among patients with limb edema, the dominant stenosis was in the central vein in seven cases and at the venous anastomosis in one case.
Two false negative results (3.6%) were found in our study, missed due to overlying bony structures on subclavian stenosis. In another series, CDS was indeterminate in 8% of the upper extremities examined because of incomplete visualization of the subclavian or brachiocephalic veins caused by artifact from bony structure. [20] In another study, detection of stenosis using color Doppler flow imaging had a sensitivity of 86% and a specificity of 60%.
Considering only stenoses of venous anastomosis, color Doppler flow imaging had a sensitivity of 100% and a specificity of 85%. [21] Turbulent blood flow causes extensive vessel wall and perivascular tissue vibration. This localized tissue vibration causes artifactual color assignment of the perivascular soft tissues, which precludes adequate visualization of the venous anastomosis. [3]
In 15 patients, the presence and location of stenoses were confirmed during the operation. This finding is consistent with that of Zibari et al. [2] A new anastomosis was created in six patients. In eight patients, the stenotic segment was resected. A new access site had to be chosen in only one patient.
The most serious cause of graft failure remains thrombosis. Thrombosis of a vascular access is diagnosed at physical examination and can easily be confirmed sonographically; typically anechoeic or hypoechoeic clot is seen within the vessel with absence of blood flow noted during pulsed or color Doppler study. [22] Sixteen patients (29.1%) in this study had complete venous thrombosis associated with no flow through AVF in 15 patients and markedly reduced flow in one. Five patients responded to anticoagulant therapy. Surgery confirmed the CDS findings in 11 patients who underwent thrombectomy with creation of a new anastomosis in four patients.
In the study of Hill et al, [18] thrombosis of the graft occurred in 32% of patients, and a total of 57 procedures were required to maintain patency of the original shunt or to place a new one. Thrombectomy of the AVF alone did not provide satisfactory results in most cases. Thrombectomy was initially successful in almost every case, but the graft remained patent for only several hours to days in most patients.
Traditional treatment of thrombosed vascular access has been thrombectomy and surgical revision; however, thrombolysis, percutaneous angioplasty, atherecromy and placement of venous stents have all been used to prolong the life of thrombosed fistulas. [23]
True aneurysmal dilatation does not require treatment but false aneurysms are always managed surgically. Although aneurysms or pseudo-aneurysm can be detected clinically, color Doppler flow imaging allows better estimation of their size, of the degree of mural thrombosis, and of the size of their neck. [21]
Increased flow rates, more than 1500 mL/min, were associated with either steal syndrome in two diabetic patients or venous hypertension in two other patients. The Doppler findings noted in steal syndrome was marked reduction of flow in distal artery, while high flow rate reaching 600 mL/min in distal venous limb of the AVF is associated with venous hypertension. Ligating the distal cephalic vein successfully treated peripheral venous hypertension and stiffness limited to the hand and distal forearm.
Arterial steal is defined as retrograde flow in the native artery distal to the anastomosis. This phenomenon is most easily demonstrated in Brescia-Cimino fistulas, in which blood flow from the ulnar artery passes through the palmar arches into the distal radial artery and subsequently courses retrograde into the low resistance fistula. Such retrograde flow can also occur with brachial artery anastomosis, as smaller vessels can act as collateral pathways. [24] In another series, [23] Placement of an AVF created a steal syndrome in seven patients, six of them were diabetic, relief of disabling symptoms required arterial bypass in two patients and graft ligation in four patients. One patient whose symptoms were limited to periods on dialysis had improved over time with conservative therapy.
In conclusion, CDS is a noninvasive technique that allows the assessment of both anatomy and hemodynamics of an AVF. This technique is free of any known risk, cheap and can be used at the bedside. CDS outlines the AVF lumen and allows definition of lumen dimensions and detection of luminal encroachment. The technique also provides important information to the surgeon, thereby potentially increasing the number of AVF reconstruction rather than new shunts. Combined CDS and Doppler flow assessment will ultimately become the ideal imaging for HD access routes. Routine serial sonographic examination can detect complications early enough to improve fistula survival and decrease patient morbidity. Most major complications can be repaired without limb loss and with shunt salvage.
| Acknowledgement | | |
The author of this manuscript acknowledge Dr. Mohamed A. El-Sharawy Associate professor and consultant, vascular surgery, King Fahd Hospital of the University, Al-Khobar, Saudi Arabia who has contributed to the study by making substantial contributions to conception and design of this study.
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Correspondence Address:
Khaled M Moghazy
Department of Radiology, King Faisal University, Dammam
Saudi Arabia
 Source of Support: None, Conflict of Interest: None  | Check |
PMID: 19112217 
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5] |
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