Novel technique for estimating urethral tissue compliance for stricture detection

Urethral strictures are a pathologic condition that predominantly impacts the male population following trauma. Voiding efficacy is decreased as a result of spongiofibrosis and scar tissue formation, increasing the stiffness of the urethra and narrowing the urethral diameter. The current gold standard study used to diagnose urethral stricture disease is a retrograde urethrogram (RUG), an x-ray imaging technique that illuminates the urethra by injecting contrast through the tip of the penis. However, there is a large variability in the length and location of a stricture determined by different physicians. Furthermore, there is no indication of tissue quality from the static RUGs. As such, patients are counseled regarding the potential for multiple surgical techniques and possible need to harvest buccal mucosa graft from the oral cavity, depending on the severity and length of the fibrosis. A novel technique was developed to locate the stricture by estimating the compliance of the tissue along the length of the urethra using a sequence of RUGs showing urethral distension. The urethra was considered to be an elastic cylindrical tube; one-dimensional conservation of mass and momentum equations with a constitutive relation were used to model the flow through it. By considering the patient-specific length and location of the stricture and the compliance of the tissue, patients can be better counseled on the most appropriate surgical intervention preoperatively.