Arteriovenous fistulas (AVFs) are recommended for hemodialysis access when possible. A noncannulatable but otherwise well functioning AVF leads to prolonged catheter dependency and frustration for the patient and the renal health care provider team. Difficult cannulation patients include obese individuals in whom cannulation sites are too deep, and others with vein segments that are short, tortuous, or otherwise difficult to palpate. The Venous Window Needle Guide for Salvage of AV Fistulae (SAVE) trial was designed to evaluate the efficacy and safety of the Venous Window Needle Guide (VWING; Vital Access Corp, Salt Lake City, Utah) device for salvage of such noncannulatable AVFs that are otherwise functional.