A Novel Endoluminal Ultrasound Imaging Technique to Determine Urethral Luminal Cross-Sectional Area

Retrograde urethrogram (RUG) and voiding cystourethrogram (VCUG) are currently the gold standard imaging technique for diagnosis of urethral stricture and determination of stricture location. However, RUG and VCUG have multiple limitations. These techniques require exposure to ionizing radiation, the quality is operator and patient dependent, there is a moderate degree of invasiveness with urethral catheterization, can have artifacts because of patient positioning that underestimates stricture length. The development of novel imaging modalities without ionizing radiation to accurately evaluate the presence, location, length, and lumen cross-sectional area (CSA) of the urethral stricture would be of great value. The objective of this study was to develop a novel endoluminal ultrasound (ELUS) imaging technique that permits the accurate quantitation of urethral stricture.

Urethral strictures were created in rabbits (n = 5) by electrocautery and an ELUS technique was developed for subsequent luminal imaging. A 3.2F 40 MHz ultrasound (US) probe was introduced transurethrally and infused with US contrast agent. Images were recorded as the catheter was pulled back at a constant speed to acquire tomographic images. Lumen CSA over the entire urethral length was calculated using a custom methodology and validated in our laboratory.

Urethral luminal CSA over the entire length of urethra before and after experimental stricture development was quantified including the length of stenosis. Intra- and interobserver variability (r = 0.99 for both) was excellent.

Feasibility of ELUS as a quantitative technique to determine healthy urethral lumen and stricture CSA was demonstrated. The translational potential for a nonionizing imaging modality to better describe CSA, length, location, and uninvolved urethral CSA of the stricture is a significant improvement over current methodology.