The primary cause of dysfunction in 80% of AVGs is neointimal hyperplasia at the GV anastomosis site, though degeneration of the cannulation zones due to repetitive trauma over time can also be a contributing factor [1,2]. Other common complications of AVGs include pseudoaneurysms, steal phenomenon, infection, and seromas.

Iatrogenic graft-to-vein fistulas can develop when the vein near the cannulation zone is frequently punctured and as a result of increased intragraft pressure caused by GV anastomosis stenosis. This condition can lead to increased blood flow through the abnormal connection of iatrogenic graft-to-vein fistula. Although the exact prevalence has not yet been reported, it is considered a rare complication. In some cases, it can have clinical significance, such as causing partial thrombosis in the venous limb of the graft, which leads to dysfunction due to the steal phenomenon [3-6].

Resolving venous outflow obstruction with PTA may not be sufficient to manage iatrogenic graft-to-vein fistulas. We present a case where another endovascular option was utilized when abnormal fistulous flow persisted.

A 76-year-old male patient with ESRD (End-Stage Renal Disease) of unknown etiology, along with hypertension and gout, underwent the placement of a radial-median cubital straight prosthetic straight graft in the left forearm on March 21, 2023, due to suboptimal vessel conditions in the forearm cephalic vein. On January 3, 2024, the patient presented with clinically significant AV access dysfunction, reporting high venous pressure during dialysis. He was referred to the angiosuite for PTA.

During the physical examination, an abnormal bruit was noted at the proximal graft, while a complete loss of thrill was detected in the distal portion of the graft. A shuntogram was then performed via a 7-French vascular sheath (Prelude Short Sheath Introducers, Merit Medical, Utah, USA) using an antegrade approach. Imaging revealed thrombotic occlusion in the distal half of the straight graft and the formation of a fistula between the graft and an adjacent vein at the proximal cannulation zone (Fig. 1). Using an angled angiographic catheter (Impress, Merit Medical, Utah, USA), the occluded segment of the distal graft and the GV anastomosis were accessed. After selecting the outflow veins, venograms of the upper arm draining veins and central veins were performed, revealing normal findings.

Figure 1. A shuntogram was obtained via a vascular sheath in the antegrade direction, revealing occlusion in the distal segment of the AVG. The stump of the thrombotic-occluded distal graft is indicated by black arrowheads. An anomalous fistula formation around the proximal cannulated area of AVG is noted with black arrows.

The GV anastomotic stenosis was treated with a 6mm x 6cm non-compliant ultra-high pressure balloon catheter (Athletis, Boston Scientific, Marlborough, USA), achieving full effacement. Declotting of the thrombotic distal half of the graft was performed using an antegrade Hoffman sheath (COOK, Bloomington, USA), with any residual wall-adherent thrombi removed using a compliant balloon Fogarty catheter (Edwards Lifesciences, Puerto Rico, USA). Declotting of the arterial limb was then carried out via a retrograde sheath using a Forgarty balloon catheter. The post-procedure shuntogram confirmed clearance of the thrombus. However, residual stenosis greater than 30% remained, and a flow diversion (steal phenomenon) into the iatrogenic fistulous tract between the graft and vein was observed. Additional long-duration balloon dilation (5 minutes) was performed at the GV anastomosis, followed by a 3-minute balloon tamponade to address the iatrogenic graft-to-vein fistula. Despite reestablishing outflow at the GV anastomosis, significant flow through the iatrogenic graft-to-venous fistula persisted (Fig. 2).

Figure 2. After declotting of AVG and PTA for GV anastomosis, considerable amount of fistulous flow (white arrows) was remained. Normal AVG flow was noted using black arrows.

To occlude the fistulous tract and maintain graft patency, a vascular covered stent (COVERA plus, Bard Peripheral Vascular, Arizona, USA) was implanted (Fig. 3). Following the procedure, the fistulous tract was successfully closed and collaterals were disappeared. Postoperatively, the patient has been receiving hemodialysis successfully without any issues related to blood flow or cannulation for approximately 280 days.

Figure 3. Following the deployment of a vascular covered stent (white arrowheads) within in the graft, all abnormal iatrogenic graft-to-venous flow was disappeared.

Cannulation technique is crucial for synthetic PTFE grafts, particularly with the use of the rope-ladder method, as it helps prevent repetitive trauma. In contrast, bottonhole cannulation can lead to aneurysmal degeneration and AV access infection [7,8]. It is also important to avoid puncturing both the graft and the adjacent veins simultaneously, as this can cause hematoma and iatrogenic fistula formation. Proper needle penetration when accessing overlying veins and adequate compression after needle withdrawal are essential for maintaining AVG patency.

Iatrogenic graft-to-venous fistulas are uncommon conditions, and only a few case reports exist, leaving their clinical significance not fully defined. Some fistulas, especially those of small caliber, may resolve naturally, but they can also result in prosthetic graft thrombosis on the venous side due to the steal phenomenon [6]. In the presented case, occlusion at the GV anastomosis was a common observation in dysfunctional AVGs, with symptoms likely resulting from increased intragraft pressure and repetitive iatrogenic injury to both the graft and adjacent vein. The fistula developed at the proximal cannulation zone, functioning as the proximal outflow vein, while the distal venous segment of the AVG became occluded. The anomalous connection of iatrogenic graft-to-vein fistula become more prominent.

Although no standardized treatment for iatrogenic graft-to-vein fistulas exists, some reports suggest that balloon dilatation of the GV anastomosis alone may be a definitive treatment [6]. In cases where the thrombotic occluded segment of the AVG cannot be negotiated, stents have been used to re-direct outflow venous flow created by the fistula [3,5]. Other case reports describe embolization to directly treat the fistulous tract [9]. While there is no standardized approach, maintaining adequate flow within the access circuit is crucial. In this case, although balloon angioplasty was initially considered the definitive treatment for the GV anastomosis, a large fistulous tract and the associated steal phenomenon persisted, necessitating treatment with a covered stent to maintain access circuit patency.

Repeated cannulation trauma can lead to perigraft scar formation and fibroblastic neointimal ingrowth and stenosis. The first-line treatment for stenosis in the cannulation zone is balloon angioplasty, and stent placement in this area is generally discouraged [8]. However, some advocate for stent or stent-graft placement as a salvage option in selected cases [1,2]. While stent-graft used for aneurysms in the cannulation zone may not be suitable for immediate cannulation, those used for stenosis can often be cannulated the day after insertion [2]. In this case, primary patency was well-maintained, and cannulation was permitted after a two-week follow-up. Nonetheless, this treatment should be considered in special circumstances.

All authors have and declare that: (i) no support, financial or otherwise, has been received from any organization that may have an interest in the submitted work; and (ii) there are no other relationships or activities that could appear to have influenced the submitted work. (iii) There no presentations in academic contests.