A physician with an idea for a medical device must know what he or she wants, but cooperation with a designer determines how to get it. My feeling has always been that tossing an idea to an engineer isn't enough to create a product or solve a problem.

As founder of a team creating a next-generation non-vascular stent, I was determined that physician input provide a strong clinical base upon which the medical design team could innovate with confidence. This new stent concept was born in 2001, after recognizing and analyzing all the deficiencies of current urological stents, including stents I developed 15 years ago. The plan was to improve the design and material to prevent unwanted complications associated with stent use.

A collaboration emerged in which both physician and device designer could have their say. The initial team, consisting of myself (a urologist and stent expert), and a mechanical engineer with stent experience, began by examining the available permanent and temporary non-vascular stents.

We found that permanent stents for the urinary tract were all adapted for prostatic and urethral or even for ureteral use by changing the caliber or the length of the basic vascular-stent design. In other words, we had the male equivalent of Chinese foot binding: trying to get the organ to fit the stent instead of the other way around.

Although temporary urological stents available during the 90s and early 2000s were designed for the prostate and urethra, their radial rigidity caused irritation. This rigidity at the vicinity of the sphincter also disturbed the contraction of the sphincter, producing incontinence. Overall, the stents only partly addressed the requirements of urologist treating patients with prostatic or anterior urethral obstructions.

We needed to make structural changes to suit anatomy and function of the target organ. The first sketches and prototypes came out of our initial discussions. My clinical experience vastly contributed to the shape and the materials we would need: the stent skeleton had to be super-elastic and couldn't be heated or chilled for expansion or contraction because of the danger to surrounding tissue. The cover had to be strong but inert to withstand the hostile chemical environment of urine and with surface characteristics to reduce crystal deposition.

The goal was to remove a large caliber stent from the urethra in a secure way and without trauma. The concept we came up with was a simple feature where the stent unravels into a narrow ribbon-like strand during its removal from the patient's body with a minimum of discomfort.

The engineers and I worked together throughout prototyping and in-vitro testing, as well as the human feasibility tests. Having the physician and engineer accompany one another throughout testing meant that our discussions weren't theoretical but took place in the lab or over the operating table. We documented all testing stages on video or in still pictures, then reviewed them with the team, which now included an expert in biocompatible polymers. There were, of course, differences of opinion, but we always kept our end-goal in mind.

What came from this close cooperation was the first easily removable, self-expandable, large caliber, fully covered stent designed for the urinary and biliary tracts. The self-expanding components of this family of stents are made of Nitinol, and entirely covered, like a sleeve, with a thin, strong biocompatible co-polymer to make it an impermeable tube preventing tissue ingrowth. Despite their large caliber, the new stents allow easy insertion and easy endoscopic removal.

Close cooperation gave us a rapid development turnaround time for producing the final prototypes — a little over two years. Moreover, because the visionary and the engineer capable of turning vision into reality were both present at all stages of design and clinical testing, we didn't have to make changes to the stent after it became available for patient use. The only modifications were to the delivery systems which made it more user-friendly and affordable.

The resulting technological platform exceeded expectation, as it can be adapted for designing temporary and permanent stents for almost any potential stent-treatable site. The platform allows for the production of large-caliber, thin walled, entirely covered stents that fit organ function and are easily removed. Ureteral and biliary stents based on this platform have already been approved for sale in Europe, and stents for other sites are in various phases of testing and clinical trials.