One discussion this week included the relationship between vein size and fistula failure.
Reference: Bashar K, et al. The role of venous diameter in predicting arteriovenous fistula maturation: when not to expect an AVF to mature according to pre-operative vein diameter measurements? A best evidence topic. International Journal of Surgery. 2015 Mar;15:95-99. doi: 10.1016/j.ijsu.2015.01.035.
Summary: This best evidence topic was investigated according to a described protocol, and asked the question: what is the minimal vein diameter that can successfully predict maturation of an arteriovenous fistula (AVF) in patients undergoing dialysis?
The search retrieved 804 papers, of which 5 represented the best evidence to answer the clinical question. All studies assessed the association between successful AVF maturation and the size of vein used.
- The strongest evidence came from a non-randomised controlled follow-up study in which 76% of fistulas created using >2 mm cephalic vein successfully matured compared to 16% when the vein measured ≤2 mm.
- Another prospective, multicentre study showed 65% successful maturation using veins >4 mm compared to 45% with veins < 3 mm. Vein diameter was found to be an independent predictor of maturation in multivariate regression analysis in two retrospective observational studies.
- A retrospective observational study found that using venous measurements of ≥2.5 mm following tourniquet application resulted in more fistulas been created that would have otherwise been denied based on venous ultrasound mapping.
- Routine use of tourniquet makes it possible to form AVFs in patients who otherwise would have been rejected. One study showed good results from using a transposed BBAVF when a BCAVF was deemed inappropriate following US.
In conclusion, a vein diameter of <2.5 mm should be considered inadequate for formation of an AVF, particularly if those measurements remain unchanged following the use of tourniquet.