Percutaneous echoguided drainage of retroperitoneal collections is to be considered a recommendable technique which guarantees a good percentage of success and a complete resolution of the effusions and also gives a low percentage of complications. The drainage can be made through a simple percutaneous needle puncture or through a catheter which is kept for some days. The latter technique done by Seldinger or Trocar's method, guarantees more possibilities of success. The systemic echographic control during the post-operatory period of the urological patients have permit to find out the high frequency of small fluid effusions (haematic, urinary or lymphatic) in the operation area; not all the collections need a treatment. The urinary collections or those with clinical signs of anemia have to be drained. In the presence of small haematic or lymphatic collections, the ultrasonography follow-up shows almost always a progressive volume reduction with a following disappearance. Percutaneous drainage has to be performed in the presence of a large collection (more than 5 cm of diameter), in the case of a persistent collection or when patient presents with clinical features of infection.