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

INTRODUCTION & OBJECTIVES: Retrograde urethrography (RUG) and voiding cystourethrography (VCUG) are currently the gold standard imaging technique for diagnosis of urethral stricture disease 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 due to patient positioning that underestimate stricture length. The development of novel imaging modalities without ionizing radiation to accurately evaluate urethral stricture presence, location, length and lumen cross-sectional area would be of great value. The objective of this study is to develop a novel endoluminal ultrasound (ELUS) imaging technique that permits the accurate quantitation of urethral stricture.

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

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

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