Duplex and colour flow sonography in the diagnosis of post-biopsy arteriovenous fistulae in the transplant kidney.

Arteriovenous fistulae are a common sequel to percutaneous biopsy of the transplant kidney. The majority close spontaneously, but a proportion progress and may require embolization or surgical closure. They are characterized by a very pulsatile (arterialized) venous flow. The arteries sometimes demonstrate a low resistive index and/or high velocities, but normal values may be encountered. On colour flow Doppler the most characteristic appearance is a mosaic of colour due to a combination of tissue vibration and turbulence.