ACCURACY OF DUPLEX ULTRASOUND IN THE DIAGNOSIS OF HAEMODYNAMICALLY SIGNIFICANT STENOSES IN FAILING RADIOCEPHALIC FISTULAE.

Therese Daley(1), Alexandre Chao(2), Lisa Hockey(1), Simon Gruenewald(1), George Larcos(1), Elizabeth Yuill(2), Richard Allen(2).
Departments of Nuclear Medicine & Ultrasound(1) and Surgery(2), Westmead Hospital, Westmead NSW

ASUM'99 - Winner of the Medical Applications Best Clinical Presentation Award

INTRODUCTION
Patients with chronic renal failure require adequate vascular access for successful haemodialysis. Sites for access in these patients are often limited. Native radiocephalic fistulae are the preferred permanent vascular access site as they pose the least complications. However, they do develop progressive flow limiting lesions which may lead to significant stenosis and/or graft thrombosis. Malfunctioning fistulae are a frequent cause of hospitalisation, therefore, early detection of stenosis is important to increase graft longevity. The conventional imaging method for evaluation of problematic fistulae is angiography. With the recent advances in high resolution ultrasound, Doppler has been suggested as an alternative method. To date however, criteria described in the literature for stenosis at the arterial anastomotic site and the efferent run-off veins has been poorly defined.

AIM
The objective of this study is to determine what Doppler parameters should be used to diagnose a >50% stenosis by comparison with angiography.

METHOD
The indications for ultrasound evaluation in our patient population included poor flow during dialysis, cannulation problems, high venous pressures, suspected graft thrombosis and arterial steal from the palmar arch. Twenty-seven patients were included in this study with an age range of 16-71 years (mean age 49 years). All examinations were performed by one of two sonographers with a sonologist using an ATLHDI 3000 or 5000. Both 10-5MHz and 7-4MHz linear transducers were employed. The radial artery and cephalic veins were examined in the forearm up to the antecubital fossa using real time, colour and pulsed Doppler. Peak systolic velocities (PSV) and end diastolic velocities (EDV) were recorded in the proximal radial artery, the arterial anastomosis, the distal radial artery, the anastomotic bulb region and the proximal, mid and distal cephalic vein. Particular attention was paid to any area of the fistulae which had lumen narrowing and/or colour Doppler aliasing. Pre stenotic velocities were measured in order to calculate velocity ratios. The patient's blood pressure was recorded on the contralateral arm at the time of the examination. Angiography was performed within 4 weeks of the Doppler examination.

RESULTS
If using the listed criteria when assessing the radial arterial anastomosis the following accuracies were achieved:

Criteria used:

When assessing the cephalic vein the following accuracies were achieved:

Criteria used:

The anastomotic bulb region was difficult to assess and problems were encountered due to high turbulent flow and the possibility of a concurrent radial artery lesion which may mask a bulb lesion. Due to these problems, no definite velocity criteria was able to be obtained.

CONCLUSION
Our study found Doppler ultrasound to be a highly sensitive and specific modality for evaluating radiocephalic fistulae when compared with angiography. We found the described Doppler criteria to be the most accurate methods to determine >50% stenosis. Further investigation of these results by using a prospective approach is necessary to confirm the accuracy of Doppler in the assessment of native radiocephalic fistulae.