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Ultrasonography |
1 From the Departments of Radiology (M.L.R., T.M.W.), Surgery (M.H.G., M.H.D., C.J.Y.), and Nephrology (M.A.), University of Alabama Hospital at Birmingham, 619 19th St, South, JTN358, Birmingham, AL 35249-6830. From the 1999 RSNA scientific assembly. Received December 28, 1999; revision requested January 30, 2000; revision received February 25; accepted March 2. Address correspondence to M.L.R. (e-mail: mrobbin@uabmc.edu).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS: US assessment of the upper extremity arterial and venous anatomy was performed in 70 patients with chronic renal failure before surgical evaluation. The surgeon documented the planned access procedure, which was based on physical examination results, and then reviewed the US preoperative mapping report. The surgical procedure and outcome were recorded.
RESULTS: Fifty-two of the 70 patients who underwent mapping had vascular access placement. Preoperative US mapping resulted in a change in the planned surgical procedure in 16 (31%) of the 52 patients. An AVF rather than the planned graft was placed in eight (15%) patients. The AVF placement rate increased from 32% (126 of 395 patients) to 58% (30 of 52 patients). Unsuccessful surgical explorations decreased from 11% (28 of 256) to 0%.
CONCLUSION: Preoperative US mapping before hemodialysis access placement can result in a change in surgical management, with an increased number of AVFs placed and an improved likelihood of selecting the most functional vessels preoperatively. Further study is needed to determine longer term outcomes.
Index terms: Arteries, US, 918.12983, 918.12984, 918.12989 • Dialysis, shunts, 918.457 • Fistula, arteriovenous, 918.457 • Grafts • Ultrasound (US), Doppler studies, 918.12983, 918.12984 • Veins, US, 916.12983, 916.12984, 916.12989
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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AVFs that are never usable and early graft failures are associated with the common problem of inadequate vessel (artery or vein) selection. The surgeon’s preoperative physical examination is the primary basis for AVF versus graft selection (5). Only palpable veins are considered for construction of AVFs, and the more proximal draining venous anatomy is not known prior to the operation. The work of Silva et al (6) suggests that ultrasonographic (US) preoperative data on nonpalpable and proximal veins, as well as on arterial inflow, improve the rate of appropriate AVF or graft selection. We therefore implemented a program to increase the anatomic data available to the surgeon by using preoperative US. The purpose of this prospective analysis was to assess the effect of preoperative US mapping on surgical selection and placement of AVFs and grafts. In addition, the effect of US mapping on negative surgical exploration rates—that is, no suitable vessels for access creation found at surgery—was evaluated.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Fifty-two of the 70 patients who underwent US mapping had vascular accesses placed. Eighteen patients did not undergo surgery by April 1, 1999: They either missed their surgical appointment, went to an outside surgeon and thus were unavailable for follow-up, or elected not to have a hemodialysis access placed at that time.
Twenty-three (44%) of the 52 patients (29 female, 23 male; mean age, 47 years; age range, 11–77 years) were diabetic. Forty (77%) patients had a history of previous central catheter placement or major surgery in which a central catheter may have been placed, and 13 (25%) had a history of a catheter placed on the same side as the planned hemodialysis access.
At completion of US, a staff sonographer or board-certified staff radiologist with special expertise in US recorded the pertinent US measurements on a data worksheet designed for this study. All images, including waveforms and measurements, were archived on 5
-inch magneto-optical disks. At a later date, one sonologist (M.L.R.) reviewed all the images to verify the worksheet data. A final US interpretation was rendered with discussion and agreement in cases of interpretation discrepancy.
All US examinations were performed by using a 5-MHz or higher linear transducer with a model XP/128 ART or Sequoia unit (Acuson, Mountain View, Calif) or an HDI 3000 or 5000 unit (Advanced Technology Laboratory, Bothell, Wash). The US laboratory at the University of Alabama Hospital at Birmingham is accredited by the Intersocietal Commission for the Accreditation of Vascular Laboratories and the American College of Radiology.
US Mapping Technique
The preoperative diameter criteria used for adequate upper extremity surgical results at our institution are (a) all arteries 2.0 mm or larger and (b) all veins, both in the forearm and upper arm, 2.5 mm or larger for AVF creation, or veins 4.0 mm or larger for graft creation (6). Anteroposterior vessel diameters are measured in the transverse plane, with a minimum amount of pressure on the vessel.
Forearm Mapping
The patient’s arm is comfortably positioned at approximately 45° from the body, with the elbow resting on a Mayo stand. Antegrade radial arterial flow is documented at the wrist level, and the radial arterial diameter is measured. If the radial arterial diameter is less than 2.0 mm, the ulnar arterial diameter is measured at the wrist. If neither the radial nor ulnar artery is 2.0 mm or larger, the arteries are not suitable for forearm AVF creation. In this case, the upper arm is then assessed as detailed in the next section.
A tourniquet is placed at the middle forearm, assuming that an adequate radial or ulnar artery is identified as previously described. The entire distal forearm is percussed for 2–3 minutes, similarly to the percussion maneuvers performed prior to intravenous placement, with special attention given to the cephalic vein and the other dorsal forearm veins.
The cephalic vein diameter at the wrist is measured. If the diameter is 2.5 mm or larger, the cephalic vein is followed toward the elbow. The diameter and location of cephalic vein branches in the forearm that are larger than 1.0 mm are recorded. The tourniquet is then sequentially placed in the antecubital area and cranial upper arm, and the cephalic vein is followed to its insertion into the subclavian vein. A forearm cephalic vein AVF is still possible if the cephalic vein is occluded or smaller than 2.5 mm in the upper arm, as long as the forearm cephalic vein drains into an acceptably sized forearm median cubital vein and brachial or basilic vein (to the subclavian vein).
If the cephalic vein diameter at any point in the forearm or upper arm is less than 2.5 mm, the dorsal and volar regions of the forearm are searched for other veins. If a suitable vein is found, a transposition AVF may be possible. The draining vein is assessed for stenosis or occlusion in the upper arm.
Upper Arm Mapping
If no suitable forearm vein is found, the brachial arterial diameter is measured at the antecubital space. A tourniquet is placed near the axilla, and the cephalic, basilic, and brachial veins from the antecubital area to the cranial aspect of the upper arm are examined. No percussion maneuvers are performed in the upper arm, because we have found that they are not helpful in vein distension. Veins of acceptable diameter are followed into the subclavian vein to assess for stenosis or occlusion by using visual inspection and compression techniques.
Draining Veins
All draining veins are assessed for stenosis and thrombosis throughout their course with visual inspection and compression. Adequate vein diameter is confirmed into the deep veins. Drainage into the deep venous system is confirmed with color Doppler imaging.
Indirect Assessment of Central Veins
Subclavian and jugular venous Doppler waveforms are analyzed for indirect evidence of central venous abnormality. Indirect evidence of stenosis or occlusion in the nonvisualized brachiocephalic vein and/or superior vena cava include diminished respiratory phasicity and diminished transmitted cardiac pulsatility in the subclavian and jugular veins (7–9). If diminished respiratory phasicity is found, we perform Valsalva and sniff maneuvers to determine whether flow drops to the baseline. If one side—either the right or left—is abnormal, the contralateral side is examined to assess for abnormal waveforms.
Hemodialysis Access Selection Criteria
An optimal access is recommended on the basis of the US evaluation of the patient’s anatomy, according to the following preferential order of access placement (Table):
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2.5-mm) forearm median cubital vein and brachial or basilic vein also is acceptable. Figure 1 shows a cephalic vein and a brachial artery that are adequate for forearm AVF placement.
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Forearm (loop) graft.—An adequately sized brachial artery and antecubital draining vein in the forearm are suitable.
Upper arm (straight) graft.—There is no acceptable vein-artery combination in the antecubital space. An adequately sized brachial artery and cranial basilic or brachial vein are suitable.
Surgical Correlation
After the patient’s physical examination was performed and a medical history was obtained, but before the US mapping results were reviewed, the surgeon documented the planned access procedure. Correlation was performed to determine which access type—AVF or graft—the surgeon actually placed after reviewing the preoperative US mapping results. The surgical outcomes were recorded. The effect of US mapping on negative surgical exploration rates also was evaluated. The results were compared with recent historical data (4,10).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The negative exploration rate during this interval decreased to 0% (0 of 52) compared with 11% (28 of 256) previously (10). Brachiocephalic vein and/or superior vena cava stenosis was detected with US mapping preoperatively in three (60%) of five cases and subsequently proved at venography or surgery. An example of abnormal subclavian venous respiratory phasicity in a patient with subsequently proved brachiocephalic venous stenosis is shown in Figure 2. Thirty (58%) of the 52 patients had an AVF placed compared with 126 (32%) of 395 patients in our previous experience without use of preoperative mapping (4).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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US is a noninvasive method that is commonly used in vascular assessment; however, to our knowledge, there are few articles in which US vessel mapping prior to hemodialysis access placement has been investigated. Comeaux et al (13) found that 66% (33 of 50) of patients who had not undergone surgery previously had vascular abnormalities at preoperative US mapping. Silva et al (6) successfully used preoperative duplex Doppler vascular mapping to decrease early access failure rates and increase the percentage of AVF placements. However, the immediate changes in surgical management based on US mapping results were not addressed in that study.
With US, vessels can be assessed for size, stenosis, and occlusion. The increased anatomic knowledge obtained with US mapping assists in surgical planning and during the surgery itself and is especially valuable in patients who are difficult surgical cases (eg, obesity, diabetes, history of prior access, elderly women). Vein problems are common in these patients, and, thus, physical examination may be difficult.
In our study patient population, US mapping of the upper extremity vessels resulted in a change in the type and location of access surgery performed in 31% (16 of 52) of patients. Fifty percent (eight of 16) of the affected patients received an AVF rather than the planned graft. We observed a substantial increase in the percentage of patients who received AVFs compared with the percentage of patients in a previous historical study group—58% (30 of 52 patients) versus 32% (126 of 395 patients) (4); these data corroborate the results of Silva et al (6). Another patient received a forearm graft rather than an upper arm graft, and, thus, the upper arm was saved for future access when the current access fails.
The rest of the patients whose surgery changed as a result of US mapping (seven of 16 [44%]) avoided negative explorations. A decrease in negative explorations is desirable, especially with the wound healing problems that are common in these patients. There is also the potential for decreased operating room time and cost.
Overall, we observed a substantially decreased rate of unsuccessful explorations—0% (0 of 52) versus 11% (28 of 256) historically (10). The surgeons have found that when US mapping results indicate that no suitable veins are present, none are found. Accordingly, we no longer perform explorative surgery to see whether there is suitable anatomy for graft or AVF placement. The surgeons also report having increased confidence in the presence of a vein if it was mapped. They may take extra time to find a reported vein to create an access in an obese or otherwise technically difficult arm rather than abandoning the site. Thus, preoperative US mapping is now performed in all our patients prior to hemodialysis access placement.
As with any new examination, there is a substantial learning curve with US mapping. Until the various AVF and graft configurations are understood, study interpretation may be difficult. When few veins are present, both the forearms and the upper arms may need to be examined. In these instances, US mapping can be a long and tedious procedure. In our experience, roughly five to 20 examinations are needed for proficiency. A typical examination of both forearms and one or both upper arms performed by an experienced sonographer takes 45 minutes. The subclavian vein is examined on the side where suitable anatomy is found. Complete bilateral examinations are not performed if an anatomy appropriate for a forearm fistula is found.
Although preoperative US mapping is performed at few institutions, at some, preoperative venograms are obtained routinely in all patients. Well-known venographic complications include phlebitis and thrombosis, often in the vein that is ideal for access placement. Venography cannot provide the accurate arterial and vein diameter measurements that are provided by US mapping. In addition, some veins, such as a patent cephalic vein in the upper arm with a thrombosed cephalic vein in the forearm, may not be filled at venography. Nephrologists may want to avoid intravenous contrast material administration in those patients with renal insufficiency who are not yet undergoing dialysis. At our institution, we obtain venograms only in selected patients at high risk for central venous abnormalities from previous catheter or access placement. This practice has not changed with the addition of preoperative US mapping.
US-based detection of nonvisualized stenosis of the central veins is not as sensitive as direct visualization of arm vein stenosis. The presence of central venous stenosis must be inferred on the basis of Doppler analysis results and other clues rather than from direct venous compression and thrombus visualization (7). In the current study, only three (60%) of the five cases of proved central venous stenosis were detected preoperatively. Therefore, patients at high risk for central venous stenosis should undergo venography or magnetic resonance venography. It is important that venography be used specifically to evaluate the central venous circulation to avoid false-negative diagnoses (Fig 3).
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Larger patient numbers and longer follow-ups are needed to determine whether there is a substantial corresponding decrease in the early graft failure rate and an increase in AVF maturation. The results of further studies will determine whether preoperative US mapping can lead to a decrease in the number of surgical procedures needed to achieve a successful long-term AVF or graft.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Abbreviation: AVF = arteriovenous fistula
Author contributions: Guarantor of integrity of entire study, M.L.R.; study concepts, M.L.R., M.A., M.H.G.; study design, all authors; definition of intellectual content, M.L.R., M.H.G., M.A.; literature research, M.L.R.; clinical studies, M.L.R., M.H.G., M.H.D., C.J.Y., T.M.W.; data acquisition, M.L.R., M.H.G.; data analysis, M.L.R., M.H.G., M.A.; manuscript preparation, M.L.R., M.H.G., M.A.; manuscript editing, all authors; manuscript review, M.L.R.
This paper received the Larry Mack Award at the 1999 Annual Meeting of the Society of Radiologists in Ultrasound.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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