How do you decide when to refer for an access angiogram in a patient on hemodialysis with a drop in Kt/V but no other signs of access dysfunction?

In a JASN study (Coyne et al., PMID 9259360), the 3 comment causes of low Kt/V were:

• 42%- from poor blood cleaning due to low blood flow or shortened HD time
• 25% - due to recirculation from access dysfunction or reversed needles
• 33% - no cause identified, but on subsequent monthly testing, it normal...

I would first repeat the Kt/V to make sure it is consistently low. I do think the next step would be to evaluate the access. One should also pay attention to other labs (phosphorus, potassium, BUN) in order to confirm that there is a problem.

Kt/V can be operator dependent (mistakes), so that alone would not prompt me to get an access angiogram; I would need something else: a repeat Kt/V that has fallen, Unexplained new hyperkalemia or increasing azotemia, or high venous or arterial pressures on HD, or prolonged bleeding post decannulati...