How a Fistula is Like a Marriage

Latin, fistula, ...ae; A shepard’s pipe, or a tube; a sewer pipe.

Every medical student that rotates through surgery here knows the definition of a fistula by heart. Ask one and he or she will reply, “An abnormal connection or tract between two epithelialized surfaces.” They will learn the “Friends of the Fistula” or the eponymous mnemonic that delineates those conditions that foster fistula formation.

Most surgeons try and get rid of them. I make them.

I am, as you have probably guessed, an access surgeon.

It seems so simple, to enjoin, in hemodialytic matrimony, one artery to one vein and allow the union to mature so that enough blood courses through this new system that we can extract a blood volume, three days a week, send it to a machine, filter it, osmotically purify it and send it back into the patient. And all of this purifying takes place in a few hours, using only the patient’s own tissue, the dialysis machine, and two stainless steel needles.

On the face of things though, it shouldn’t work. The output of the unwed brachial artery is nowhere near what is required for dialysis, much less the radial artery, whose output is less than half that of the clinically insufficient upstream pipe. But marry the artery to a vein, and something magical happens. Well, not magical perhaps, but definitely fortuitous for us and our vulnerable kidneys or our patient’s kidneys, and the nephrologists who care for them and the surgeons that get to do these things. The marriage of artery and vein tricks the upstream vessel into thinking that the arm is violently exercising, the way a confidence man dupes a wealthy patsy into gladly giving over a bit of dosh. The drop in pressure across the arterial bed signals the artery to relax, and markedly increase its flow as if it were engaged in the most arduous task, the most menial of manual, repetitive labor. It can signal a ten-fold increase in radial artery flow over the course of a few weeks. And this allows that little bitty radial artery to have as much flow as a racehorse’s kidney getting lasix for the first time. Or so I’m told.

But it doesn’t always work. In fact, its track record is not much better than the best ball player’s batting average. Only about four in ten fistulas created go on to mature without needing any further work. We can increase that number with interventions, but a significant number never meet the needle. The vein is simply not meant to handle that much flow. It’s like asking your teenage son to get a job and get good grades. It sounds good, but it’s too much to ask of the thing. They’d rather be doing something else, with less stress in their lives.

So when I see that patient post-op, with the beautifully maturing vein, without a tourniquet, easily viewed from across the room in a raking light, wiggling slightly during systole, I can’t help but smile a little. The feel of the thing, the thrill, is aptly conjoined to the feeling I have for the thousand little cat’s whiskers that caress the mechanoreceptors of my index and middle finger as I palpate that life-sustaining cord on the patient’s arm. Even better when the feeling extends up the arm and doesn’t peter out, thick and robust like a bodybuilder’s cutaneous vein at full flex and on display.

Forgive me if a wax poetic on the mundane arteriovenous fistula; but for the patient who needs dialysis, it is a precious thing, usually hard won, having endured surgery and procedure and catheter and showerless days and nights to win this inestimable little thing, to say nothing of the pain in the prize of continuing to endure a hardscrabble life on this earth and its inherent iniquities. I get more than a little thrill in seeing one of these things mature, ready to use, ready to sustain life for this patient, even if it condemns her to a lifetime of needling and regularly scheduled malaise; but the alternative being worse, this road is less rocky and mostly endurable.

And in this setting, for this patient, I can do no better. It is slightly wondrous, every time I get to write, “May initiate cannulation, per protocol, of this patient’s new fistula.”

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