**3.2.4.4 CT guidance**

The puncture can be performed into the collecting system without preoperative opacification of the collecting system. CT scan is essential in patients with organomegaly such as hepatomegaly and splenomegaly, severe skeletal abnormalities such as scoliosis and kyphosis, morbid obesity, and previous major intraabdominal surgical interventions. (Haaga et al., 1977)
