After an arteriovenous fistula is created, it must "mature". In general, fistulas require a three-to-six month growth period as the vein subjected to higher pressure and blood flow becomes larger and tough enough to be cannulated in two places three times a week. As the goal of creating more fistulas has gotten more attention, actual performance in maturing fistulas to usefulness has been examined. Studies show a wide variance in maturation success rates, from 20 to 90%.

Generally accepted guidelines call for re-evaluation of a newly created fistula if it has not been deemed usable by 6 months. Assessment can include applying objective criteria to the fistula, such as protocolized ultrasound examinations and blood flow measurements, or a "gestalt" test can be administered by an experienced access surgeon or dialysis professional. My practice is to more aggressively re-evaluate fistulas when the patient is being dialyzed via a catheter, since the "clock is ticking" and it is only a matter of time until an infected catheter or central stenosis will occur. Slow growth is expected, and sometimes it is reasonable to give more time to achieve the goal, but frequently growth is stymied by anatomic problems which prevent further growth in a reasonable time. In these instances, action to correct the limitation will be necessary to restore the growth curve.

Many factors can interfere with the maturation of fistulas, and awareness of these factors should be included in the assessment process. The office ultrasound machine allows a better understanding of the developing anatomy of a fistula, and frequently identifies or suggests these limiting factors. A specific strategy for each type of problem is important. Waiting for the problem or difficult patient to go away is not a strategy.

Inflow stenoses are common in wrist and elbow level cephalic fistulas. The cephalic vein is frequently smaller between the wrist and the dorsal branch two inches up the forearm, and also between the antecubital fossa and the lateral branch several inches up from the elbow. Small clamps placed on the veins during surgery may injure the vein and create scarring and stenosis. In either location, a catheter can be placed in the fistula above the stenosis directed retrograde for contrast studies and balloon dilation of the narrow segment. A standard arterial angiogram from the leg out to the arm can also be useful in diagnosing and dilating inflow stenoses. This "minimally invasive" approach is frequently successful, and can be repeated as often as necessary.

An option for stenoses at the wrist is to abandon the venous segment between wrist and dorsal branch, and reattach the fistula at the dorsal branch where it is naturally larger to the radial artery slightly higher. The vessels are bigger, and more flow can be expected, but some length will be sacrificed, and the new fistula will be shorter.

Stenoses just above the elbow are more difficult to revise if venoplasty fails, as the brachial artery and cephalic vein tend to be further apart on opposite sides of the biceps muscle. Nevertheless, the cephalic can be freed and transposed across the biceps to meet the brachial artery several inches above the elbow, a larger lateral branch can sometimes be moved across in similar fashion, or a jump graft can bridge the gap.

Stenoses in mid-fistula or in the outflow are also known, and are generally signaled by pulsatility in all or part of the fistula. Stenoses in the "swing-zone" between the transposed and in-situ portions of the basilic vein in transposed basilic fistulas are very common. A swollen arm after placement of an AV fistula or graft frequently occurs due to central stenosis from catheters left in too long.

Again, fistulography, venoplasty, and (rarely) stenting are employed to diagnose and treat fistulas which are unusable because of pulsatility or other problems. Fortunately, venoplasty is usually successful in resolving the problem, although redilation may be necessary at intervals as scarring and stenosis recurs. The role of the "cutting balloon" recently approved by the FDA in reducing failure of venoplasty, or reducing the necessary frequency of dilations, remains to be defined. Revision can also be necessary, and the most rational course is sometimes to abandon a complicated and dysfunctional forearm fistula in favor of a surer upper arm fistula option.

Unlike grafts, fistulas can have branches which sometimes divert flow away from the desired "central channel" one wishes to develop for dialysis cannulation. One big vessel is far more usable than several smaller channels. Ligation of these branches through small incisions under local anesthesia can be safe and effective in redirecting blood flow in a more desirable direction. Caution should be exercised, however: multiple prominent branches should raise the question of whether there actually is a viable central channel, or whether there is an obstruction in what seems to be the main vessel. In this case, ligating multiple branches creates venous hypertension in the hand, and solves nothing. A careful ultrasound exam, or a concurrent fistulogram performed by the surgeon at the time of ligation provides maximum information, effectiveness and safety.

Once cleared for use, many patients experience a difficult phase as the dialysis personnel "learn the fistula". Infiltrations and problems do occur. Too many problems over too long a time should prompt a re-evaluation of the fistula to smoke out overlooked adverse factors. Ultrasound exam or fistulography may be indicated.

Re-intervention to promote maturation of fistulas should not be regarded as a sign of failure, and no shame should be attached to a corrective procedure. Not all veins are ideal, and not all fistulas develop without help. The patient should be informed of these realities right up front before the first operation is done, and access surgeons should be proactive in monitoring new fistulas and acting appropriately to help them along. The end result - more useful fistulas for dialysis and less complications for the patients - is worth the added effort.