Ureteric stents are tubes of memory coded polymeric bio-inert material which recoil or angle at both ends after being straightened for insertion. Placed so that one end remains in the renal pelvis and the other in the urinary bladder, most stents contain a central channel, with multiple holes throughout its length. The Towers stent, an exception, drains through guttered channels on the outside of the stent, is little used, and is associated with more steinstrasse