Percutaneous nephrostomy is an interventional radiology/surgical procedure in which the renal pelvis is punctured whilst using imaging as guidance. Images are obtained once an antegrade pyelogram (an injection of contrast), with a fine needle, has been performed. This contrast is used to show calcifications at the renal pelvis. A nephrostomy tube may then be placed to allow drainage. Percutaneous nephrostomy is an interventional radiology/surgical procedure in which the renal pelvis is punctured whilst using imaging as guidance. Images are obtained once an antegrade pyelogram (an injection of contrast), with a fine needle, has been performed. This contrast is used to show calcifications at the renal pelvis. A nephrostomy tube may then be placed to allow drainage.