**4.1 Early complications/early failure**

It is defined as AVF which fails to mature or unable for use up to 3 months after creation. Causes of early failure may be related to inadequate arterialinflow, stenosis at anastomosis or outflow issues due to underlying fibrosis of vein. Various causes for early failure or complications are listed below:


## **4.2 Late complications/late failure**

Fistula Failure occurring after 3 months duration after creation of AVF are classified as late failure. Various complications are seen like; Stenosis, aneurysm, steal syndrome, infection, cardiac failure, venous hypertension, median nerve injury.

## *4.2.1 Thrombosis*

Thrombosis is noted within the fistula in early as well as late Postoperative period. Early thrombosis is most often related to an inflow issues and late thrombosis due to an outflow stenosis. Either of these can result in thrombosis of the fistula if left untreated. Difficult cannulation, sudden reduction in VA flow or a new onset low flow in VA should trigger the possible diagnosis of thrombosis. Physical

examination may show absent thrill in AVF and pulsatile anastomosis is felt. On USG and CDI, the affected vein may be dilated and show echogenic thrombus filling the lumen with no internal color filling. Partial thrombus is also seen. Needle insertion sites should be evaluated carefully as there may be partial thrombus at these sites. In case of thrombosis in draining vein, AVF itself shows no evidence of aliasing color flow and the feeding artery shows triphasic normal spectral waveform instead of biphasic spectral waveform seen in working AVF.
