The use of local anesthetic gel during retrograde urethrography: does it cause a false negative result?

To investigate the implication of topical urethral anesthetic gel on the evaluation of retrograde urethrography (RGU) MATERIAL AND METHODS: In this prospective study, 20 patients with a mean age of 46 years were enrolled. All these patients were subjected to RGU because of suspecting a urethral stricture. Of these 13 had a history of open or endoscopic urethral manipulation, while seven had no such history. In all patients 10 ml of Gelicain gel 2% (lidocainhydrocloride) was used as local anesthetic gel at temperature of 22 degrees C. The injection was made gradually over 10 s. The first set of RGU was done without local anesthesia and the second image was taken after 10 min of instillation of 2% gelicain gel. All images were evaluated by the same radiologist. The diameter of the urethra was measured by capture screen during fluoroscopy immediately distal to the stricture site in case of urethral strictures and at the middle of the bulbous urethra in other cases.

In all patients, the mean diameter of the urethra at the selected site was 8.7 +/- 2.5 mm before and 9.4 +/- 2.9 mm after instillation of local anesthetic gel (P = 0.005). The stricture was diagnosed in 13 cases while seven patients had no stricture. The clinical diagnosis of a possible stricture was the same before and after instillation of the local agent in all patients.

Instillation of the local anesthetic gel before RGU produces a slight but statistically significant increase in the diameter of the urethra at the selected sites. However, neither the radiologic reading of RGU nor the clinical diagnosis of a possible stricture was changed because of this increment.