A surgeon told me that as a fistula enlarges there will be more accessory vein flow. Not sure what his point was. Certainly we think that fistulas will not clot at lower access flow rates as compared to grafts because of these accessory ( “ collateral”) veins maintaining outflow. I am perplexed how frequently the accessory veins involute in larger fistulas. Classic example is a well -developed BC avf that presents with subtotal occlusion of the cephalic arch and there are no longer any accessory/collateral veins draining to the basilic/brachial veins. What caused the attrition of these collateral pathways that were present when the fistula was created? The fistula vein became the pathway of least resistance to flow as the fistula matured. Early in the maturation of the fistula, one could still demonstrate that the accessory veins were still there if a reflux study was done with outflow compression. But later as the fistula became much larger and one discovers an outflow occlusion or development of high inflow the accessory/collateral veins did not enlarge to accommodate the outflow. What causes this attrition; thrombosis in the much smaller veins?
I guess the other question is why don’t some accessory veins involute when there is no longer an outflow restriction in a developing immature fistula. I see this more commonly in an immature forearm RC avf that has now been dilated to 8 mm and multiple accessory veins remain even a year later. Seems like the physics of flow don’t explain all the findings of the shunts that are man- made.
Does anyone know of any anatomy/pathology studies that document the presence of valves in these small accessory veins. I would assume they have valves but I don’t know.
Thank you for any thoughts or feedback about accessory veins.
Jeffrey Hoggard MD
Capital Nephrology Assoc
3031 New Bern Ave
Raleigh, NC 27610
Cell: 252 -531-9556