MDCT angiography with 3D image reconstructions in the evaluation of failing arteriovenous fistulas and grafts in hemodialysis patients

ACR Appropriateness Criteria® Dialysis Fistula Malfunction

The creation and maintenance of a dialysis access is vital for the reduction of morbidity, mortality, and cost of treatment for end stage renal disease patients. One's longevity on dialysis is directly dependent upon the quality of dialysis. This quality hinges on the integrity and reliability of the access to the patient's vascular system. All methods of dialysis access will eventually result in dialysis dysfunction and failure. Arteriovenous access dysfunction includes 3 distinct classes of events, namely thrombotic flow-related complications or dysfunction, nonthrombotic flow-related complications or dysfunction, and infectious complications. The restoration of any form of arteriovenous access dysfunction may be supported by diagnostic imaging, clinical consultation, percutaneous interventional procedures, surgical management, or a combination of these methods. This document provides a rigorous evaluation of how variants of each form of dysfunction may be appraised and approached systematically. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Arteriovenous access in hemodialysis: A multidisciplinary perspective for future solutions

In hemodialysis, vascular access is a key issue. The preferred access is an arteriovenous fistula on the non-dominant lower arm. If the natural vessels are insufficient for such access, the insertion of a synthetic vascular graft between artery and vein is an option to construct an arteriovenous shunt for punctures. In emergency situations and especially in elderly with narrow and atherosclerotic vessels, a cuffed double-lumen catheter is placed in a larger vein for chronic use. The latter option constitutes a greater risk for infections while arteriovenous fistula and arteriovenous shunt can fail due to stenosis, thrombosis, or infections. This review will recapitulate the vast and interdisciplinary scenario that characterizes hemodialysis vascular access creation and function, since adequate access management must be based on knowledge of the state of the art and on future perspectives. We also discuss recent developments to improve arteriovenous fistula creation and patency, the blood compatibility of arteriovenous shunt, needs to avoid infections, and potential development of tissue engineering applications in hemodialysis vascular access. The ultimate goal is to spread more knowledge in a critical area of medicine that is importantly affecting medical costs of renal replacement therapies and patients’ quality of life.

Imaging of Patients with Complex Hemodialysis Arterio-Venous Fistulas using Time-Resolved Dynamic CT Angiography: Comparison with Duplex Ultrasound

To evaluate the feasibility and potential on therapy management of time-resolved dynamic computed tomography angiography (dCTA) in patients with forearm arterio-venous fistula (AVF)/arterio-venous grafts (AVG). Thirty-five patients with complex failing forearm AVF/AVGs were examined with ultrasound and a dCTA protocol. Diagnosis and therapy management was evaluated versus duplex ultrasound (DUS) in three different readouts: 1. all dCTA datasets; 2. one arterial phase of the dCTA dataset; 3. one arterial and one venous dataset out of the dCTA dataset. All reads were performed >30 days apart from each other. Using all data of the dCTA examination, 20 patients were classified as having a stenosis >50%, 12 high-shunt flow, 11 partial thrombosis, 5 venous aneurysms and 5 complete thrombosis of their AVF/AVG grafts. This lead to 13 additional pathologic findings not visible on DUS and reclassification as normal in one patient with suspected AVF stenosis and complete thrombus on DUS. These additional findings lead to a direct change of therapeutic management in 8 patients. Compared to readout 1 (53 pathologies), readout number 2 and 3 revealed only 33 and 41 pathologies, respectively. dCTA provides additional information, improving diagnostic confidence and leading to changes in therapy management when compared to DUS alone.

Radiological Assessment of Vascular access in Haemodialysis Patients

Clinical examination is still the most important diagnostic tool and duplex ultrasonography is the imaging method of first choice. Radiological assessment of vascular access for haemodialysis includes preoperative analysis of vessel anatomy and postoperative surveillance for access maturation as well as diagnosis in vascular access insufficiency. Compared to ultrasonography digital subtraction angiography is superior for the evaluation of the central veins and allows diagnosis and treatment in one session. Computed tomography should only be used in patients with inconclusive ultrasonography results, for example, for the assessment of the central veins and visualization of the vascular tree. Gadolinium-enhanced magnetic resonance imaging is no longer recommended in dialysis patients, because it may trigger nephrogenic systemic fibrosis. In patients with a history of previous central venous catheters additional preoperative imaging of the central veins should be performed. In this article we review the different radiological imaging methods for preoperative assessment and suspected vascular access dysfunction.

Effect of the time to intervention on the outcome of thrombosed dialysis access grafts managed percutaneously

PURPOSE

We aimed to investigate the effect of the time interval from the clinical presentation of a thrombosed dialysis access graft to intervention on procedure success.

MATERIALS AND METHODS

Records from two academic institutions for patients who underwent percutaneous thrombectomy of occluded surgical hemodialysis graft access sites in interventional radiology from 2006 to 2011 were reviewed retrospectively. The following data were recorded: gender, age, time and date of the initial request for a thrombectomy and the procedure, age of the surgical access, angiographic outcome, and clinical outcome (successful or unsuccessful postinterventional dialysis). Univariate and multivariate logistic regression were used to evaluate whether the time to intervention significantly affected the study endpoint.

RESULTS

In total, 268 percutaneous thrombectomies were performed in 139 patients. Of these 224 (83.5%) were categorized as successful and 44 (16.4%) as unsuccessful. The time to intervention was 19.9±30.1 vs. 22±35 hours for successful and unsuccessful procedures, respectively. The difference between the two was not significant, and there were also no significant differences in covariate distributions between successful and unsuccessful outcomes.

CONCLUSION

During the first 72 hours following clinical presentation of a thrombosed dialysis access graft, time to intervention may be considered independent of procedure outcome.

Diagnostic accuracy of computer tomography angiography and magnetic resonance angiography in the stenosis detection of autologuous hemodialysis access: a meta-analysis

Purpose

To compare the diagnostic performances of computer tomography angiography (CTA) and magnetic resonance angiography (MRA) for detection and assessment of stenosis in patients with autologuous hemodialysis access.

Materials and Methods

Search of PubMed, MEDLINE, EMBASE and Cochrane Library database from January 1984 to May 2013 for studies comparing CTA or MRA with DSA or surgery for autologuous hemodialysis access. Eligible studies were in English language, aimed to detect more than 50% stenosis or occlusion of autologuous vascular access in hemodialysis patients with CTA and MRA technology and provided sufficient data about diagnosis performance. Methodological quality was assessed by the Quality Assessment of Diagnostic Studies (QUADAS) instrument. Sensitivities (SEN), specificities (SPE), positive likelihood ratio (PLR), negative likelihood values (NLR), diagnostic odds ratio (DOR) and areas under the receiver operator characteristic curve (AUC) were pooled statistically. Potential threshold effect, heterogeneity and publication bias was evaluated. The clinical utility of CTA and MRA in detection of stenosis was also investigated.

Result

Sixteen eligible studies were included, with a total of 500 patients. Both CTA and MRA were accurate modality (sensitivity, 96.2% and 95.4%, respectively; specificity, 97.1 and 96.1%, respectively; DOR [diagnostic odds ratio], 393.69 and 211.47, respectively) for hemodialysis vascular access. No significant difference was detected between the diagnostic performance of CTA (AUC, 0.988) and MRA (AUC, 0.982). Meta-regression analyses and subgroup analyses revealed no statistical difference. The Deek’s funnel plots suggested a publication bias.

Conclusion

Diagnostic performance of CTA and MRA for detecting stenosis of hemodialysis vascular access had no statistical difference. Both techniques may function as an alternative or an important complement to conventional digital subtraction angiography (DSA) and may be able to help guide medical management.