Background Arteriovenous fistulas (AVF) for hemodialysis frequently fail to mature due to inadequate dilation or early stenosis. The pathogenesis of AVF non-maturation may be related to preexisting vascular pathology: medial fibrosis or micro-calcification may limit arterial dilation, and intimal hyperplasia may cause stenosis. Study design Observational study. Setting & Participants Chronic kidney disease patients (N=50) undergoing arteriovenous fistula (AVF) placement. Predictors Medial fibrosis, microcalcification, and intimal hyperplasia in arteries and veins obtained during AVF creation. Outcome and Measurements AVF non-maturation. Results AVF non-maturation occurred in 38% of patients despite attempted salvage procedures. Preoperative arterial diameter was associated with upper arm AVF maturation (p=0.007). Medial fibrosis was similar in patients with non-maturing and mature AVFs (60±14 vs 66±13%, p=0.2). AVF non-maturation was not associated with patient age or diabetes, even though both variables were significantly associated with severe medial fibrosis. Conversely, AVF non-maturation was higher in females than males, despite similar medial fibrosis in both sexes. Arterial micro-calcification (assessed semi-quantitatively) tended to be associated with AVF non-maturation (1.3±0.8 vs 0.9±0.8, p=0.08). None of the arteries or veins obtained at AVF creation had intimal hyperplasia. However, repeat venous samples obtained in 6 patients during surgical revision of an immature AVF exhibited venous neointimal hyperplasia. Limitations Single center study. Conclusion Medial fibrosis and micro-calcification are frequent in the arteries used to create AVFs, but do not explain AVF non-maturation. Unlike previous studies, intimal hyperplasia was not present at baseline, but developed de novo in non-maturing AVFs.

SummaryBackground and objectives Arteriovenous fistulas often fail to mature, and nonmaturation has been attributed to postoperative stenosis caused by aggressive neointimal hyperplasia. Preexisting intimal hyperplasia in the native veins of uremic patients may predispose to postoperative arteriovenous fistula stenosis and arteriovenous fistula nonmaturation.Design, setting, participants, & measurements This work explored the relationship between preexisting venous intimal hyperplasia, postoperative arteriovenous fistula stenosis, and clinical arteriovenous fistula outcomes in 145 patients. Venous specimens obtained during arteriovenous fistula creation were quantified for maximal intimal thickness (median thickness=22.3 mm). Postoperative ultrasounds at 4-6 weeks were evaluated for arteriovenous fistula stenosis. Arteriovenous fistula maturation within 6 months of creation was determined clinically.Results Postoperative arteriovenous fistula stenosis was equally frequent in patients with preexisting venous intimal hyperplasia (thickness.22.3 mm) and patients without hyperplasia (46% versus 53%; P=0.49). Arteriovenous fistula nonmaturation occurred in 30% of patients with postoperative stenosis versus 7% of those patients without stenosis (hazard ratio, 4.33; 95% confidence interval, 1.55 to 12.06; P=0.001). The annual frequency of interventions to maintain arteriovenous fistula patency for dialysis after maturation was higher in patients with postoperative stenosis than patients without stenosis (0.83 [95% confidence interval, 0.58 to 1.14] versus 0.42 [95% confidence interval, 0.28 to 0.62]; P=0.008).Conclusions Preexisting venous intimal hyperplasia does not predispose to postoperative arteriovenous fistula stenosis. Postoperative arteriovenous fistula stenosis is associated with a higher arteriovenous fistula nonmaturation rate. Arteriovenous fistulas with hemodynamically significant stenosis frequently mature without an intervention. Postoperative arteriovenous fistula stenosis is associated with an increased frequency of interventions to maintain long-term arteriovenous fistula patency after maturation.

Background Arteriovenous fistulas (AVFs) often fail to mature, but the mechanism of AVF non-maturation is poorly understood. Arterial micro-calcification is common in patients with chronic kidney disease (CKD), and may limit vascular dilatation, thereby contributing to early postoperative juxta-anastomotic AVF stenosis and impaired AVF maturation. This study evaluated whether preexisting arterial micro-calcification adversely affects AVF outcomes. Study Design Prospective study. Setting & Participants 127 patients with CKD undergoing AVF surgery at a large academic medical center. Predictors Preexisting arterial micro-calcification (≥1% of media area) assessed independently by von Kossa stains of arterial specimens obtained during AVF surgery and by preoperative ultrasound. Outcomes Juxta-anastomotic AVF stenosis (ascertained by ultrasound obtained 4-6 weeks postoperatively); AVF non-maturation (inability to cannulate with 2 needles with dialysis blood flow ≥300 ml/min for ≥6 sessions in 1 month within 6 months of AVF creation); and duration of primary unassisted AVF survival after successful use (time to first intervention). Results Arterial micro-calcification was present by histology in 40% of patients undergoing AVF surgery. The frequency of a postoperative juxta-anastomotic AVF stenosis was similar in patients with or without preexisting arterial micro-calcification (32% vs 42%; OR, 0.65; 95% CI, 0.28-1.52; p=0.3). AVF non-maturation was observed in 29%, 33%, 33%, and 33% of patients with <1%, 1%-4.9%, 5%-9.9%, and ≥10% arterial micro-calcification, respectively (p=0.9). Sonographic arterial micro-calcification was found in 39% of patients and was associated with histologic calcification (p=0.001), but did not predict AVF non-maturation. Finally, among AVFs that matured, the unassisted AVF maturation (time to first intervention) was similar for patients with and without preexisting arterial micro-calcification (HR, 0.64; 95% CI, 0.35-1.21; p=0.2). Limitations Single center study. Conclusions Arterial micro-calcification is common in patients with advanced CKD, but does not explain postoperative AVF stenosis, AVF non-maturation, or AVF failure after successful cannulation.

Background Arteriovenous grafts (AVGs) are prone to neointimal hyperplasia leading to AVG failure. We hypothesized that pre-existing pathologic abnormalities of the vessels used to create AVG (including venous intimal hyperplasia, arterial intimal hyperplasia, arterial medial fibrosis, and arterial calcification) are associated with inferior AVG survival. Study Design Prospective observational study. Setting & Participants Patients with chronic kidney disease undergoing placement of a new AVG at a large medical center who had vascular specimens obtained at the time of surgery (n=76) Predictor Maximal intimal thickness of the arterial and venous intima, arterial medial fibrosis, and arterial medial calcification. Outcome & Measurements Unassisted primary AVG survival (time to first intervention) and frequency of AVG interventions. Results 55 patients (72%) underwent interventions and 148 graft interventions occurred during 89.9 years of follow-up (1.65 interventions per graft-year). Unassisted primary AVG survival was not significantly associated with arterial intimal thickness (HR, 0.72; 95% CI, 0.40-1.27; p=0.3), venous intimal thickness (HR, 0.64; 95% CI, 0.37-1.10; p=0.1), severe arterial medial fibrosis (HR, 0.58; 95% CI, 0.32-1.06; p=0.6), or severe arterial calcification (HR, 0.68; 95% CI, 0.37-1.31; p=0.3). The frequency of AVG interventions per year was inversely associated with arterial intimal thickness (relative risk [RR], 1.99; 95% CI, 1.16-3.42; p<0.001 for thickness <10 vs >25 μm); venous intimal thickness (RR, 2.11; 95% CI, 1.39-3.20; p<0.001 for thickness <5 vs >10 μm); arterial medial fibrosis (RR, 3.17; 95% CI, 1.96-5.13; p<0.001 for fibrosis <70% vs ≥70%), and arterial calcification (RR, 2.12; 95% CI, 1.31-3.43; p=0.001 for <10% vs ≥10% calcification). Limitations Single center study. Study may be underpowered to demonstrate differences in unassisted primary AVG survival. Conclusions Pre-existing vascular pathologic abnormalities in CKD patients may not be significantly associated with unassisted primary AVG survival. However, vascular intimal hyperplasia, arterial medial fibrosis, and arterial calcification may be associated with a decreased frequency of AVG interventions.

This review concentrates on the diagnosis and management of early surgical complications following pancreas transplantation. The financial implications of surgical outcomes in pancreas transplantation are also discussed.