Asymptomatic large extracapsular renal pseudoaneurysm following kidney transplant biopsy.

Vascular complications after kidney biopsy include hematomas, arteriovenous fistulas, and pseudoaneurysms. Ultrasonography is a useful tool for the diagnosis of these complications, and color Doppler scan is effective at distinguishing among them. We describe a transplant patient who underwent percutaneous kidney biopsy in whom echography performed after biopsy showed a pulsatile hypoechoic perinephric mass of 4.4 cm. This collection illuminated with color Doppler and connected to the transplant. Color Doppler scanning of the mass showed high-velocity turbulent flow within the cavity and a jet of blood from an intrarenal segmental artery. A typical pattern biphasic flow ("to-and-fro" waveform) at the pseudoaneurysm neck on color Doppler confirmed the diagnosis of postbiopsy pseudoaneurysm. Pseudoaneurysms usually are asymptomatic, but when they cause clinical signs or risk rupture, interventional treatment is required. Supraselective coil embolization of the artery feeding the pseudoaneurysm was performed successfully in our patient. Pseudoaneurysm can mimic renal cysts on gray-scale ultrasound. We suggest that Doppler sonography be performed in cystic areas detected after biopsy to exclude pseudoaneurysm.