pyometra (7), coagulopathy, thrombocytopenia, and anticoagulant therapy (2). Finally, cystocentesis is not recommended in patients with known bladder neoplasia (2). Severe complications associated with cystocentesis, though uncommon, have been previously described especially in dogs, and include uroabdomen, septic peritonitis, and laceration of the abdominal aorta (AA) (4,8). A large study of complications of the procedure performed under ultrasonographic guide has not been previously published; in particular, the clinical and echographic features of adverse effects of cystocentesis have not been evaluated by controlled studies. The aim of this study was to determine the types of complications related to ultrasound-guided diagnostic cystocentesis (UGDC) in dogs and cats, focusing the paper on ultrasonographic features.