41.1  Commentary

Question 1

The first order of business is to determine whether the individual has a reversible condition such as obstructive uropathy, drug-induced acute tubular necrosis, or another nephrotoxic condition. Commencement of hemoaccess would be unnecessary at this time since the individual has minimal symptoms; however, the degree of renal insufficiency is sufficient to predict that it will likely be required within several months to a year. Since some access procedures require several months before they are usable, an experienced surgical specialist should be contacted to construct the hemoaccess, if the nephrologist confirms that the individual has chronic progressive renal insufficiency.1 [Q1: D]

Urgent or immediate hemodialysis is not indicated and because of the associated morbidity,catheterplacementiscontraindicatedintheabsenceofacuterenalfailure.Likewise, it is inappropriate to refer directly to the surgical specialist without determining the cause of the renal insufficiency, whether it is reversible, and whether the individual should be placedontheeligibilitylistfortransplantation.Simplyreferringtheindividualtothenephrologist is not wrong, but the best option includes the diagnostic evaluation, management of treatable etiologies, and consideration for hemoaccess assuming that commencement of hemodialysis is imminent within several months to a year. It is clear that early nephrology consultationisofbenefit,fromtheperspectiveofdirectingappropriate­therapy.2–5 Likewise, early consideration of hemoaccess options facilitates preservation of vascular assets and reduces the incidence of catheter placement and the subsequent morbidities.

Question 2

The complete clinical vascular examination is an important adjunct to surgical planning and may direct the surgeon to either upper extremity; clearly the non-dominant upper extremity is preferred, unless a preferred access option is only available in the dominant extremity.Whilerelianceontheclinicalexaminationalonemaybeaccurateinmanycases, experience currently suggests that valuable information is contributed by the non-invasive ultrasound survey.6–9

While reliable DU examinations may not be available in all practice situations, it does provide the “best” option by decreasing the likelihood of unsuccessful operations while increasing the options for autologous conduit. Additional information from the duplex examination may reveal proximal vein occlusion, visible superficial veins which are postphlebitic, arterial abnormalities (location of the brachial bifurcation, occlusive disease, inadequate palmar arch collateralization, large branch veins, and relative size of the arteries and veins).

An added reason for preoperative DU survey is that the diabetic population is the group most likely to harbor asymptomatic upper extremity arterial occlusive disease. It is unknown whether this is the reason, but functional patency of hemoaccess is usually reduced in the diabetic population.8,10,11 In obese patients the lack of visible superficial veins may be countered by duplex examination; the depth of the veins precludes clinical identification and may mask prior thromboses. The depth of an otherwise acceptable vein is an important consideration and may mandate transposition to a more superficial site. Failure to identify superficial upper extremity veins on clinical examination is not an acceptablerationaleforcommencingaccessatalowerextremitysite;evenifnosuperficial veins are available, a prosthetic graft can usually be constructed between the artery and one of the deep veins in the upper extremity.

As before, there is still no indication for immediate dialysis, so that placement of a catheter at the time of the permanent access is not indicated in this clinical scenario.

[Q2: C]

Question 3

The list includes all of the usual information needed for proper operative planning. The goal istoconstructthemostdurablehemoaccessfromautogenoustissue.Whenacceptableoptions exist only in the dominant upper extremity, it is selected; thus, both arms should be studied.

Adequate arterial inflow is essential for the fistula or graft to function properly. Failure was universal with an arterial diameter <1.6 mm in one study.9 A more commonly accepted criterion is >2.0 mm diameter. Although upper extremity atherosclerotic occlusive disease is uncommon in the arm, diabetics are the group most likely to have diseased arteries, and thus it should be considered for this patient. While all vascular laboratories may not subscribe to this position, no palpable pulses were described in the core scenario such that some reassurance is needed regarding adequate arterial flow.

A key function of the preoperative duplex examination is to determine the acceptability of the superficial vein network of the forearm and arm. In addition to location and diameter, identification of large branches, occluded segments, scarring, other post-thrombotic changes, and depth of vein below the skin are all critical to success. Failure was also universal when preoperative DU identified stenotic vein segments.9 Identification of acceptable veins may increase substantially.6 Vein diameters of less than 2.5–3 mm are generally considered unacceptable, but since there is little data to support this recommendation, the practice guidelines did not incorporate a recommendation for a minimum venous diameter.7 Complete evaluation of superficial upper extremity veins should include the forearm basilic vein.6,12 Transposition of the basilic vein is usually necessary whether in the forearm or upper arm, and any vein that is too deep (greater than 0.5–1.0 cm) may need to be transposed before anastomosis.

Central vein stenoses or occlusions are usually due to prior central vein catheterizations, but the surgeon should also be wary of transvenous wires from implanted pacemakersordefibrillators.1,13,14 Fortypercentofpatientswithknownsubclavianveincatheterization had moderate to severe subclavian vein stenoses that were clinically silent.15

In the absence of an autogenous option, the surgeon should still be informed regarding the best location for the first graft. The anatomic variant of a high brachial bifurcation

occurs in ~10% of individuals. This anatomic variant may preclude placement of a prosthetic graft at a given site, but should have little adverse effect on an autogenous AVF.

Routine evaluation of the lower extremity is unnecessary, but may be considered when upper extremity sites have been completely exhausted. [Q3: E]

Question 4

This is a complex issue and the correct answer [Q4: E] is derived from a combination of experience and the recommendations of the United States Kidney Dialysis Outcomes Quality Initiative (K-DOQI). The best answer is a combination of the “best” choices summarized from the principles of all autogenous, most distal, non-dominant extremity. Thus, since almost all options are really open for this individual, the non-dominant, radiocephalic AVF is the best first choice; a potential collateral benefit is communication with (and arterialization of) the proximal basilic vein. Recognition of problems causing failure to mature are the major impediment to wider utilization of this modality.1,8–10,16 Failure to mature a forearm AVF may occur in 34–53%, and may be less attractive in the elderly, the diabetic, and female patients.8,9

The proximal options of brachial and cephalic anastomoses and transpositions have experienced a higher incidence of arterial steal and ignore the basic principle of progression from distal to proximal.1 The forearm loop graft was equated with the proximal brachial transposition by K-DOQI, but current initiatives more emphatically encourage autogenous fistula.5,16

Catheter access is to be avoided if at all possible, and is clearly not indicated in this situation; multiple autogenous options are available and commencement of dialysis is not emergent.4,5,13,14

A leftradiocephalic AVF serves the dual purpose of increasing lifetime site options, and allows the distal AVF to develop more proximal veins for subsequent autogenous hemoaccess options. A forearm vein transposition is available, but because the distal forearm vein is post-thrombotic, the proximal vein would combine with transposition of an upper arm vein as well.12,17

Question 5

Although this is a common clinical question, informed decisions are difficult since there is a paucity of concrete data. There is little data to support any course of action, and the correct answer is based upon opinion.1 [Q5: C] Clearly a healed wound, a palpable thrill, and unobstructed flow are essential. Two weeks is generally considered early for an AVF, and the minimum recommended interval is 6–8 weeks. For prosthetic grafts, 2–3 weeks is usually satisfactory, as long as the edema has resolved sufficiently to identify the outline of the graft. Since the functional patency is so low, a prosthetic AV graft should not be inserted until dialysis is imminent.1

A period of 6–8 weeks is an arbitrary interval often used in practice and supported by K-DOQI. However, if at all possible, a longer interval is preferable, since a matured access is more likely to provide durable function.