Colour Doppler ultrasound assessment of well-functioning mature arteriovenous fistulas for haemodialysis access.
BACKGROUND: A well-functioning mature arteriovenous fistula is essential for the maintenance of haemodialysis in patients with chronic renal failure. The Brescia-Cimino arteriovenous fistula has the best survival characteristics and low rate of complications. The most common reason of fistula failure is thrombosis caused by stenosis. Colour Doppler ultrasonography has proven to be effective in the assessment of anatomical vascular features. The majority of studies were done in patients with clinically presumed arteriovenous fistula complications. However, only limited data are available about the well-functioning mature arteriovenous fistulas. The purpose of the present study was to evaluate completely asymptomatic, mature arteriovenous fistulas with colour Doppler ultrasound. MATERIALS AND METHODS: From July 2001 to April 2003, we examined 139 patients with the end-stage renal disease. They were in the range of 19-79 years of age (mean, 46.7 years). The study included only the patients who met the following criteria: (1) no difficulties with haemodialysis (as reported by nurses); (2) normal venous diastolic blood pressure (<150 mmHg) at monthly evaluation; (3) normal urea clearance x time/urea volume of distribution; (4) blood cells count, plasma electrolytes, and liver function at monthly evaluation. The mean fistula age was 26 months (S.D.=21.9). The mean time of dialysis therapy was 49 months. Thirty-eight percent patients had primary fistulas, 23%--secondary, 11%--third and 11%--fourth, 4%--fifth, 5%--sixth, and 8% patients had more than sixth. RESULTS: There was no correlation between: (1) patient's age and fistula age; (2) patient's age and number of fistulas in one patient; (3) fistula age and number of fistulas in one patient; (4) localization of fistula and fistula age. There was a strong correlation between dialysis therapy period and number of fistulas in one patient. The mean flow volume was 1204.1 ml/min (S.D.=554). It was significantly higher in the fistulas with aneurysms, calcifications and tortuous vessels and lower in those with stenosis. There was no correlation between the flow volume or presence of stenosis and fistula age. Stenosis was detected in 64% fistulas. Fifty-seven percent of stenoses were located in the anastomotic region, 22% stenoses were in vein junction, 19% were at one or both ends of aneurysm, and 2% in the remaining region of the efferent vein. Perivascular colour artefacts were present at the 94% fistulas with stenosis. Chronic venous occlusion with collateral veins was detected in 6% of fistulas. The aneurysms were observed in 54% fistulas. The mean diameter of aneurysms was 12.4 mm. Ninety-six percent of aneurysms were located at puncture sites. Ten patients had a small thrombus in an aneurysm and at puncture sites. CONCLUSIONS: We conclude that there was a high level of abnormalities present in well-functioning mature arteriovenous fistulas. However, these abnormalities were not sufficient to affect the functioning of the dialysis fistula.