For example, in a study comparing duplex US in symptomatic patients with venography as the reference standard, a significant yield with duplex US in addition to 90% agreement with venography was noted. The preferred threshold to detect a >50% stenosis by duplex US was suggested by a poststenotic to prestenotic peak vein velocity ratio of 2.5 [113]. Given the limitations of US in reliably assessing the culprit lesion in the thoracic cavity, there is no relevant literature to support the practical use of duplex Doppler US of the hemodialysis access in evaluation of a suspected CVS or occlusion, suggested by swelling of the extremity ipsilateral to the hemodialysis access. MDCT angiography has been reported to accurately detect stenoses compared to DSA with a sensitivity of 95% (including all segments). However, in a study by Dimopoulou et al [84], the usefulness of MDCT angiography with 3-D image reconstruction was evaluated in the long-term assessment of hemodialysis patients with dysfunctional AVF and AVG. Poor quality of contrast enhancement was noted in 5 (5.5%) of the 92 imaged segments, which were all central in location. This phenomenon was noted in patients with multiple and/or severe stenoses in the AVF or AVG. A pseudostenosis was depicted in the MDCT angiography images in 3 patients secondary to venous compression regional to the thoracic inlet. While this likely occurred due to prone patient positioning with the AVF Dialysis Fistula Malfunction or AVG arm in extended position above the head, similar observations have been made by Heye et al [18] who described 3 pseudostenosis artifacts secondary to venous compression. Conversely, Ko et al [115] reported 100% sensitivity and specificity of MDCT angiography of central venous stenoses with no report of any detected pseudostenosis artifacts regional to the thoracic inlet, nor suboptimal contrast opacification in the central vessels.
Dialysis Fistula Malfunction. For example, in a study comparing duplex US in symptomatic patients with venography as the reference standard, a significant yield with duplex US in addition to 90% agreement with venography was noted. The preferred threshold to detect a >50% stenosis by duplex US was suggested by a poststenotic to prestenotic peak vein velocity ratio of 2.5 [113]. Given the limitations of US in reliably assessing the culprit lesion in the thoracic cavity, there is no relevant literature to support the practical use of duplex Doppler US of the hemodialysis access in evaluation of a suspected CVS or occlusion, suggested by swelling of the extremity ipsilateral to the hemodialysis access. MDCT angiography has been reported to accurately detect stenoses compared to DSA with a sensitivity of 95% (including all segments). However, in a study by Dimopoulou et al [84], the usefulness of MDCT angiography with 3-D image reconstruction was evaluated in the long-term assessment of hemodialysis patients with dysfunctional AVF and AVG. Poor quality of contrast enhancement was noted in 5 (5.5%) of the 92 imaged segments, which were all central in location. This phenomenon was noted in patients with multiple and/or severe stenoses in the AVF or AVG. A pseudostenosis was depicted in the MDCT angiography images in 3 patients secondary to venous compression regional to the thoracic inlet. While this likely occurred due to prone patient positioning with the AVF Dialysis Fistula Malfunction or AVG arm in extended position above the head, similar observations have been made by Heye et al [18] who described 3 pseudostenosis artifacts secondary to venous compression. Conversely, Ko et al [115] reported 100% sensitivity and specificity of MDCT angiography of central venous stenoses with no report of any detected pseudostenosis artifacts regional to the thoracic inlet, nor suboptimal contrast opacification in the central vessels.