Case 9: Diagnosis & Conclusions

Case 9 Index

Diagnosis: Inflow Stenosis of Arteriovenous Fistula (AVF) 

Case Summary: Well done! Based on the history and physical examination of this patient, it is likely that this patient has an inflow stenosis of their AVF that can be confirmed with a fistulagram. Let’s take a look at the clues that suggest this problem…

First, the history that there has recently been difficulty with cannulation that was previously done without difficulty suggests an acute problem with the vascular access. Further, the patient reports that clots have been returned after cannulation – another indication of a problem. Decreased inflow into the the AVF leads to decreased blood flow velocities and can increases the risk for clot formation.

We can then use our physical examination skills to further confirm this diagnosis. We find the access to be hypopulsatile with a weak thrill – again suggesting inflow stenosis. Outflow stenosis, on the other hand, might present with HYPERpulsatility and a strong, localized thrill. Finally, the absence of pulse augmentation confirms the diagnosis of inflow stenosis.

A thorough physical examination is an integral part of the assessment of a patient’s AVF! A good physical exam can detect abnormalities earlier and can even improve the longevity of the dialysis access.

When examining an AV-fistula in a hemodialysis patient, remember to do the following (click below!):
Look
1. Look at the scar(s) – what access are you looking at? Which artery (radial or brachial) and vein (cephalic or basilic) have been connected?
2. Are there signs of infection/inflammation? (ulcerations, erythema, purulence)
3. Are there signs of ischemia (cold hand, hand pain, paresthesias, ulcerations)?
4. Are there aneurysms? If so, does the skin appear compromised or are there ulcerations?
5. Is there swelling of the arm or are there collateral veins? Look on the chest/shoulders for these veins – this finding may suggest central venous stenosis.
Listen
1. Listen for the bruit (from anastomosis to chest wall!).
It should be continuous during diastole and systole.
If it is discontinuous and high pitched, think outflow stenosis. If it discontinuous and low pitched/quiet, think inflow stenosis.
Feel
1. What is the character of the pulse? Hyperpulsatile suggests outflow stenosis, hypopulsatile suggests inflow stenosis.
2. What is the character of the thrill? (Examine from ansatomosis to chest wall!) Strong and localized thrill suggests outflow stenosis, a weak thrill suggests inflow stenosis.
Arm Elevation Test (AET) & Pulse Augmentation Test (PAT)
1. AET:Look for collapse – Lift the arm from a resting to an elevated position. if there is no collapse, think outflow stenosis
2. PAT: Look for pulse augmentation – Compress the fistula few centimeters from the arterial anastomosis, and look for augmentation of the pulse (see below) between the anastomosis and your finger. If there is no augmentation, think inflow stenosis.

Arm Elevation Test (normal outflow)

Now that we’ve diagnosed the problem, what now? Our vascular surgery and interventional radiology colleagues can help us visualize the blood flow through fistula using a fistulagram and hopefully open the stenosis using stents or fistulaplasty.

During a fistulagram, the AVF is cannulated and a small volume of dye is injected into the access. Fluoroscopy (a type of X-ray) images are then taken to visualize the vessels.  If this is not possible, revisions of the vascular access may be attempted.

The images below were taken during a fistulagram, before and after fistulaplasty of an outflow stenosis. Can you see the difference?

Outflow stenosisOutflow stenosis relieved

 

For more, take a look below:

  1. Salman L, Beathard G: Interventional nephrology: Physical examination as a tool for surveillance for the hemodialysis arteriovenous access. Clin. J. Am. Soc. Nephrol. CJASN 8: 1220–1227, 2013
  2. Beathard GA: Physical Examination of the Dialysis Vascular Access. Semin. Dial. 11: 231–236, 2007
  3. Asif A, Leon C, Orozco-Vargas LC, Krishnamurthy G, Choi KL, Mercado C, Merrill D, Thomas I, Salman L, Artikov S, Bourgoignie JJ: Accuracy of Physical Examination in the Detection of Arteriovenous Fistula Stenosis. Clin. J. Am. Soc. Nephrol. 2: 1191–1194, 2007

Case 9 Index

Case 9 Introduction
Case 9 Physical Exam
Case 9 Diagnostic Testing
NephSim