William C. Jennings

A more accurate descriptive and clinically useful diagnosis based upon pathophysiology for what is commonly referred to as venous outflow stenosis is inflow-outflow imbalance. In these cases, the total outflow capacity of the AV access is inadequate to handle the inflow volume (Qa) without an increase in pressure. The relative inadequacy of the access outflow capacity in comparison to Qa results in increased outflow resistance and a proportional increase in intraluminal pressure. The clinical indicators associated with venous stenosis are the resulting manifestations of this imbalance. The point at which this occurs is dependent upon variations in these two parameters—Qa and outflow resistance. The variations in these two parameters are considerable and reciprocal. Excessive Qa results in or can lead to an entire list of serious problems that adversely affect patient morbidity and mortality. Most studies dealing with AV access Qa reduction have been for the treatment of an existing condition rather than its prevention; however, prevention of disease rather than waiting for its development is an important tenet of medical practice. The resulting clinical picture of inflow-outflow imbalance is taken as an indication for corrective treatment. In the past, in most cases this has meant angioplasty to open the outflow if it is reduced; however, this clinical picture may be associated with an excessive Qa and angioplasty in these cases creates the risk for a further increase in Qa. It is the authors’ opinion that access flow measurements should be a part of the evaluation of these cases prior to planning treatment. Using this information, a bimodal approach to primary treatment should be adopted involving either angioplasty for cases with a low or normal Qa or flow reduction in cases with an elevated Qa.

Background The Guatemalan Foundation for Children with Kidney Diseases collaborated with Bridge of Life, a not-for-profit charitable organization, to establish a vascular access program. We reviewed our experience with graded surgical responsibility and structured didactic training, creating arteriovenous fistulas (AVF) for Guatemalan children. Methods Pediatric vascular access missions were completed from 2015 to 2023 and analyzed retrospectively. Follow-up was completed by the Guatemalan pediatric surgeons, nephrologists, and nursing staff. AVF patency and patient survival were evaluated by Kaplan–Meier life-table analysis with univariate and multivariable association between patient demographic variables by Cox proportional hazards models. Results Among a total of 153 vascular access operations, there were 139 new patient procedures, forming the study group for this review. The mean age was 13.6 years, 42.6% were female, and the mean BMI was 17.3. Radial or ulnar artery-based direct AVFs were established in 100 patients (71.9%) and ten of the 25 transposition procedures. Brachial artery inflow was required in 29 direct AVFs (20.9%). Two patients underwent femoral vein transpositions. Access-related distal ischemia was not encountered. Seven of the AVF patients later required access banding for arm edema; all had previous dialysis catheters (mean = 9, range 4–12). Primary and cumulative patency rates were 84% and 86% at 12 months and 64% and 81% at 24 months, respectively. The median follow-up was 12 months. Overall patient survival was 84% and 67% at 12 and 24 months, respectively. There were no deaths related to AVF access. Conclusions Safe and functional AVFs were established in a teaching environment within a Guatemalan comprehensive pediatric nephrology center. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information

Functioning vascular access is an essential element for life-saving hemodialysis therapy. A surgically-created arteriovenous fistula has been considered the best option for many years. Recently, two manufacturers developed systems for percutaneous/endovascular creation of an arteriovenous fistula (WavelinQ and Ellipsys). We provide a review of the available experience with these systems and discuss advantages and disadvantages.

Background: Establishing a forearm arteriovenous fistula (AVF) offers preferred cannulation sites and preserves proximal access opportunities. When a radiocephalic AVF at the wrist is not feasible and the upper arm cephalic and median cubital veins are inadequate, an AV graft or more complex access procedure is often required. Creating a retrograde flow forearm AVF (RF-AVF) is a valuable alternative where the mid-forearm median antebrachial or cephalic vein is adequate, offering forearm cannulation zones with AVF outflow through deep and superficial collaterals. We report our technique and results. Methods: We retrospectively reviewed our vascular access data base of consecutive patients during an 11-year study period where a RF-AVF established the only available cannulation target in the forearm. In addition to physical examination, all patients had ultrasound vessel mapping. Results: A forearm access was established with a RF-AVF as the only opportunity for cannulation in 48 patients. Ages were 14–86 years (median = 62 years). Forty-four percent female, 63% diabetic, 13% obese, and 29% had previous access operations. Inflow was proximal radial artery in 47 individuals and one proximal ulnar. Nine AVFs (19%) failed at 2–66 months (median 14 months). One RF-AVF was ligated due to arm edema. Follow-up was 2–111 months (median = 23.5 months). Primary and cumulative patency rates were 62% and 91% at 12 months, and 46% and 85% at 24 months. Five patients were lost to follow-up with functioning RF-AVFs (mean 41 months). Twenty-three patients (48%) died during F/U of causes unrelated to access procedures (mean 25 months). Conclusions: Establishing a reverse flow forearm AVF offers a successful autogenous access option in the forearm for selected patients with an inadequate distal radial artery and/or cephalic vein at the wrist, avoiding more complex or staged procedures and preserving upper arm sites for future use. A proximal radial artery inflow procedure is recommended.

Brachiocephalic arteriovenous fistulas (AVF) makeup approximately one third of prevalent dialysis vascular accesses. The most common cause of malfunction with this access is cephalic arch stenosis (CAS). The accepted requirement for treatment of a venous stenosis lesion is ⩾50% stenosis associated with hemodynamically abnormalities. However, the correlation between percentage stenosis and a clinically significant decrease in access blood flow (Qa) is low. The critical parameter is the absolute minimal luminal diameter (MLD) of the lesion. This is the parameter that exerts the key restrictive effect on Qa and results in hemodynamic and functional implications for the access. CAS is the result of low wall shear stress (WSS) resulting from the effects of increased blood flow and the unique anatomical configuration of the CAS. Decrease in WSS has a linear relationship to increased blood flow velocity and neointimal hyperplasia exhibits an inverse relationship with WSS. The result is a stenotic lesion. The presence of downstream venous stenosis causes an inflow-outflow mismatch resulting in increased pressure within the access. Qa in this situation may be decreased, increased, or within a normal range. Over time, the increased intraluminal pressure can result in marked aneurysmal changes within the AVF, difficulties with cannulation and the dialysis treatment, and ultimately, increasing risk of access thrombosis. Complete characterization of the lesion both hemodynamically and anatomically should be the first step in developing a strategy for management. This requires both access flow measurement and angiographic imaging. Patients with CAS present a relatively broad spectrum as relates to both of these parameters. These data should be used to determine whether primary treatment of CAS should be directed toward the anatomical lesion (small MLD and low Qa) or the pathophysiology (large MLD and high Qa).