ABSTRACT
Answer: (d) Proper technique for the standard subureteric transurethral injection (STING) therapy involves the following steps: (1) emptying the bladder to ¾ capacity so as not to displace the ureter laterally; (2) placement of the needle bevel up into the posterior portion of the ureter; (3) visualization of the creation of the mound with initial injection of 0.1 – 0.2 ml of material. Multiple injection sites implies there was difficulty in obtaining a proper mound in the correct plane, as well as increasing the possibility of leakage of injectable material. Kirsch et al reported improved results by modifying the standard technique by performing hydrodistention of the ureteral orifice and injection into the submucosa of the ureteral tunnel. 1
2. Which of the following injectable materials requires preinjection skin testing:
(a) Polytetrafluoroethylene (PTFE) (b) Dextranomer/hyaluronic acid (c) Cross-linked bovine collagen (d) Polymethysiloxane
Answer: (c)Preinjection skintestingis necessary for the use of cross-linked bovine
collagen as 3 % of patients will have a hypersensitivity reaction. However, a negative result does not completely eliminate the risk of an allergic reaction. Leonard et al describe a small subset of patients who developed antibovine collagen antibodies who had negative preinjection skin testing. While those patients became seropositive the clinical relevance is unclear. In only one of those patients a local reaction occurred which may have been immunogenic. 2
3. The mechanism of long-term sustained efficacy of dextranomer/hyaluronic acid is:
(a) Giant cell reaction and granuloma formation
(b) Fibrous encapsulation (c) Fibroblast migration and collagen
ingrowth (d) Rapid absorption and replacement with
calcium carbonate
Answer: (c) Dextranomer/hyaluronic acid is a dual component material. The dextranomer is cross-linked dextran microspheres 80 – 250 µ m in diameter in a gel of hyaluronic acid. The dextranomer, the main bulking agent, is slowly degraded by hydrolysis. The hyaluronic acid represents the transport medium and slowly dissipates over 12 weeks.
