*4.2.2 Stenosis*

It is often due to outflow stenosis. Venous stenosis is more commonly seen in AVF than AVG. However, it is common cause of failure. Swelling of upper limb, prolonged bleeding after dialysis, difficult cannulation and/or slow flow are common symptoms of venous stenosis. In radio cephalic AVF, inflow lesions due to inadequate arterial flow is confirmed by negative arterial pressure during HD session and physical examination by pulse augmentation. In brachio cephalic AVF, cephalic arch stenosis is very commonly (in up to 77% cases) seen causing failure. Cephalic arch is the final bend in cephalic vein when it enters in to axillary vein. Cephalic arch stenosis causes swelling in head and neck, high venous pressure with thrombosis. Venous or arterial stenosis can be successfully managed by angioplasty [2]. Cephalic arch stenosis warrants stent placement due to its elasticity and resistant nature to repeated angioplasty. During pre and Postoperative scanning, entire length of vessels should be traced for any possible stenosis or narrowing. PSV ratio is measured in feeding artery at the level of AVF and 2 cm proximal to it.

#### **Figure 10.**

*Gray scale image showing stenosis with post stenotic turbulent color flow and marked elevated PSV and EDV [6].*

If the PSV ratio is ≥3.0 and PSV is >400 cm/sec, stenosis is present. If the draining vein is visibly narrow, PSV is measured at stenosis and at 2 cm caudal to stenosis. If the PSV ratio is ≥2.0, stenosis is considered (**Figure 10**). Most frequent site of AVF stenosis is adjacent to anastomosis. Presence of adequate collaterals, low systemic pressure, poor Dopplerinsonation angle and central venous stenosis are some of the factors which can hinder the diagnosis of stenosis. However the degree of stenosis is not absolute in AVF failure prediction.
