What device is utilized to dilate narrow urethral strictures?

The correct choice for dilating narrow urethral strictures is the filiform catheter. This device is specifically designed for the purpose of navigating through the narrowed areas of the urethra, providing a means to gradually dilate the stricture.

The filiform catheter is a flexible, slender instrument that can maneuver through small spaces, making it especially suitable for strictures. It is often used in conjunction with a larger catheter to achieve dilation, allowing for both the restoration of urine flow and the assessment of the severity of the stricture.

Other options, such as cystolithotomy, relate to surgical procedures involving the bladder and the removal of stones, rather than treatment of urethral strictures. Metal sounds, while they may help in exploration of the urethra, are not primarily used for dilation purposes. The hydrocele refers to a fluid-filled sac surrounding the testicle and does not pertain to urethral strictures or dilation techniques.

Thus, the filiform catheter clearly stands out as the most appropriate tool for the task at hand, enabling effective management of narrow urethral strictures.