1. Patient characteristics
Median age was 17 (range, 8?19) years: 0?9 (n=3), 10?14 (n=12), 15?19 (n=32). Median body weight was 45 (range, 22?98) kg. Thirty-two male and 15 female patients were included in this study. The etiologies of chronic kidney disease were glomerulonephritis in 20 patients (42.6%), urologic causes in 8 (17.0%), hypo-dysplasia in 4 (8.5%), Alport syndrome in 4 (8.5%), nephrectomy due to malignant disease in 1 (2.1%), polycystic kidney disease in 1 (2.1%), others, including renal coloboma syndrome, neurofibromatosis, Henoch?Sch?nlein purpura, myelomeningocele, amyloidosis, in 5 (10.6%), and unknown cause in 4 (8.5%). At the time of AVF creation, 21 patients (44.7%) were undergoing HD through a CVC, 17 patients (36.2%) had not undergone renal replacement therapy, and 9 patients (19.1%) decided to convert from peritoneal dialysis to HD due to complications or insufficient dialysis. Fifteen patients (31.9%) had a previous history of transplant (Table 1).
2. Perioperative evaluation and management
Of the 52 AVFs, 43 cases were radiocephalic AVFs, 7 cases were brachiocephalic AVFs and 2 cases were forearm basilic vein transpositions. Arteriovenous grafts with prosthetic material were not performed in any of the patients. Preoperative vein mapping was performed in 12 cases and all of them were performed after January 2012 according to the revised center protocol for vascular access creation, which favored routine duplex mapping. The median diameter of the vein and artery were 27 (range, 21?47) mm and 20 (range, 14?31) mm, respectively. Ten patients were treated postoperatively with low molecular weight heparin (LMWH) and 7 of them had taken aspirin based on the immediate results of the AVFs (Table 2).
The mean follow-up duration for all AVFs was 49.7±39.2 months. At 1, 3 and 5 years, the primary patency rates for all AVFs, including cases of primary failure, were 60.5%, 51.4%, and 47.7%, respectively; primary assisted patency rates were 78.8%, 75.6%, and 72.1%, respectively; and secondary patency rates were 82.7%, 79.2% and 79.2%, respectively (Fig. 1).
When age was evaluated as a continuous variable, there was a tendency toward improved primary patency with increasing age; however the tendency was not statistically significant (hazard ratio, 0.832; 95% confidence interval [CI], 0.678?1.020; P=0.077) (Table 3). Results of Cox regression analysis indicated that no other factor, including sex, body weight, AVF type, the presence of a CVC, previous history of vascular access failure, and use of anticoagulation therapy was significantly associated with primary patency.
When the patients were grouped as <13 or >13 years old (the fourth quartile of age), there was a tendency for increased primary (39.2% vs. 65.3% at 1-year, P=0.05) and primary-assisted patency (57.1% vs. 84.2% at 1-year, P=0.05) in older patients. There was no significant difference in secondary patency (71.4% vs. 84.2% at 1-year, P=0.12).
4. Primary failure
There were 9 cases (17.3%) of primary failure. These failures occurred in 8 patients with a 17-year-old male patient experiencing two primary failures. The cases of primary failure included 6 radiocephalic AVFs, 2 brachiocephalic AVFs and 1 basilic vein transposition. The median age of the patients was 16 (range, 7?19) years and the median body weight was 32 (range, 22?62) kg. Three of these patients underwent vein mapping and the diameters of veins were 22, 27, and 36 mm, respectively and the diameters of arteries were 14, 17, and 19 mm, respectively. Four of them were subjected to anticoagulation therapy due to weak fistula flow after anastomosis or high risk for thrombosis. Primary failure occurred more frequently in patients with small body weight, when body weight was evaluated as a continuous variable (odds ratio, 0.907; 95% CI, 0.842?0.977; P=0.010).
Among the patients with primary failure, a 7-year-old boy who was treated with LMWH showed a coagulation abnormality and developed a hematoma, which was believed to be the cause for the AVF thrombosis. A 12-year-old boy kept his arm flexed for several hours and was found to have a thrombosed brachiocephalic AVF 9 days after the initial surgery. The parents no longer consented to revision of the AVF due to fear of re-thrombosis; they opted for peritoneal dialysis.
5. Maturation and complications
Excluding the cases of primary failure, the mean duration of maturation was 10.0±3.7 weeks. During the study period, 36 interventions were performed in 15 AVFs. Twelve of 36 procedures were performed during the first year after AVF creation. The mean number of interventions per AVF, including both endovascular therapy and surgery, was 0.84±1.88, which amounted to 0.20 interventions per 12 access-months. The most common procedure was balloon angioplasty for stenosis (n=23). The locations of the stenosis were juxta-anastomosis (n=13), outflow vein (n=4), multiple stenosis in outflow veins (n=5), and artery (n=1). No patient showed stenosis in the anastomosis or central veins. Others included interposition graft for stenosis (n=1), proximalization of arterial inflow (n=3), branch ligation for delayed maturation (n=2), thrombectomy (n=3), and excision of aneurysm (n=3).
6. Long-term outcomes of patients
During the study period, 20 patients (42.6%) underwent kidney transplantation and 4 of them returned to HD due to graft failure. The median duration between the AVF creation and kidney transplantation was 36 (range, 3?87) months. Among the rest of the patients, 19 patients (40.4%) continued HD, 2 patients (4.3%) converted to peritoneal dialysis and 6 patients (12.8%) were transferred to another center and were lost to follow-up.
Among the 8 patients with primary failure, 1 patient converted to peritoneal dialysis and 7 patients continued HD: 5 with a newly created functional AVF and 2 with CVC. During follow-up, 4 of them underwent kidney transplantation at 71, 64, 18, and 5 months after AVF creation.