Dialysis therapies
Flow monitoring: performance characteristics of ultrasound dilution versus color Doppler ultrasound compared with fistulography

https://doi.org/10.1016/S0272-6386(03)00786-8Get rights and content

Abstract

Background: Measurement of access blood flow is the preferred noninvasive screening test for hemodialysis arteriovenous (AV) fistula stenosis. However, performance characteristics of the 2 most frequently used ultrasound techniques compared with fistulography remain elusive. Methods: We evaluated 59 hemodialysis patients with native forearm AV fistulae who underwent all 3 measurements in a prospective order: the ultrasound dilution technique (UDT), color Doppler ultrasonography (CDUS), and fistulography. Patients with angiographically diagnosed access stenosis underwent angioplasty and were followed up by means of monthly UDT measurements until restenosis occurred within the first 6 months. Results: Both ultrasound techniques predicted access stenosis (P < 0.01). Performance was similar between both techniques, evaluated by receiver operating characteristic curves. Areas under the curve averaged 0.79 (95% confidence interval [CI], 0.66 to 0.91) for UDT and 0.80 (95% CI, 0.65 to 0.94) for CDUS. Correlation between measured UDT and CDUS blood flow rates was 0.37 (Spearman's ρ, ρ = 0.004). The calculated optimal cutoff value for the prediction of stenosis was 465 mL/min for the UDT and 390 mL/min for the CDUS technique. Access stenosis was diagnosed in 41 patients who subsequently underwent percutaneous angioplasty (PTA), which was successful in 34 patients. Restenosis occurred in 13 patients within the first 6 months after PTA. UDT access blood flow after PTA was significantly lower in these 13 patients compared with the other 21 patients. Conclusion: Our data suggest that blood flow monitoring of AV hemodialysis access by ultrasound provides a reasonable prediction of access stenosis and restenosis.

Section snippets

Study design and patients

A prospective, observational intervention study was conducted in the hemodialysis centers of the University of Vienna Medical School, Vienna, Austria. Only patients with a native forearm AV fistula as primary dialysis access were considered. Sixty-six of 69 patients in these units with a native forearm fistula were enrolled into the study. Seven patients did not complete the study because of withdrawal of signed consent (n = 4), transplantation (n = 2), or transfer to another dialysis center (n

Patient characteristics

A diagnosis of access stenosis was made by fistulography in 41 of 59 patients. The distribution of important covariates for access patency, such as patient age, sex, diabetic status, hematocrit, and previous implants of permanent catheters of previous PTAs, were equally distributed between the 2 groups. Patient demographic characteristics according to vascular access patency are listed in Table 1.

Performance characteristics of the 2 ultrasound techniques compared with fistulography

Calculation of the ROC showed an area under the curve (AUC) of 0.79 (95% CI, 0.66 to 0.91) for UDT

Discussion

Our prospective study evaluated characteristics of the 2 most widely used ultrasound techniques for the prediction of access stenoses. The UDT and CDUS performed equally, with slight advantages of the UDT in the low sensitivity range. Few studies have correlated ultrasound blood flow measurement with angiographic findings in hemodialysis patients. However, negative likelihood ratios could not be calculated in these reports, with the exception of the study by Gadallah et al,14 because

Acknowledgements

The authors acknowledge the support of the nursing stuff of the hemodialysis unit for their help in patient administration.

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Supported in part by grant no. 1675 from the University of Vienna.

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