Cook Medical (Bloomington, Indiana) has reported commercial launch of a device that will allow physicians to more easily extract kidney stones.

The NGage Nitinol Stone Extractor is smaller than existing stone retrieval devices, allowing physicians to more easily engage, release and extract stones even in the most difficult locations while providing improved irrigation, visibility and enhanced efficiency.

"Flexible ureteroscopes are small now," Jerry French Sr., senior VP and global strategic business unit leader for Cook's urology division, told Medical Device Daily. "Flexible ureteroscopes have a working channel that carries fluid and the instrument. It pushes water through the scope to assure that physicians have better vision. If the retrieval instrument is too large and takes up most of the port, your vision is not as good. Cook developed this extractor for flexible ureteroscopy."

The extractor comes in both 1.7 Fr and 2.2 Fr size with open diameters of 8 mm and 11 mm, respectively.

Traditional stone retrieval devices often are not able to grasp or release stone fragments located within the kidney or ureter, which can lead to increased patient discomfort and the need for additional extraction procedures.

"It's the smallest device of its kind on the market now," French said.

In recent clinical evaluations, the NGage proved more effective than standard devices in grasping and holding fragments in the kidney and ureter. Its retention strength was also demonstrated to be 1.5 times stronger than traditional graspers.

These studies, conducted at the University of Texas Southwestern Medical Center (UTSW; Dallas) and Oregon Health and Science University (Portland), were presented at the 2007 World Congress of Endourology in Cancun, Mexico, last November.

The NGage was FDA-cleared via 510(k) last year, but Cook is just now launching the product.

An interesting aspect of the NGage is that it's made with nitinol, a shape-memory alloy that combines nickel and titanium. It allows the extractor retains its shape following extreme torsion, yet is flexible enough for a physician to guide during stone manipulation without damage to surrounding renal tissue.

"If you used stainless steel, it might tear the mucosa," French said.

The $235 NGage looks like a tiny kitchen whisk, but with fewer wire loops. It is typically used in conjunction with lasers, which break up the stones for easier removal.

French pointed out that, unlike existing retrieval devices, NGage has no prongs. "It's a like a web, but there are no prongs that could get caught in the lining or mucosa."

Additional research studies conducted at UTSW, also presented at the Cancun meeting, showed the NGage captures and retains stones similar to a stone basket while having the releasing capabilities of a stone retrieval grasper.

Margaret Pearle, MD, professor of urology and internal medicine at UTSW, said, "Our studies ... show that NGage has 50% greater retention strength than traditional graspers. The device also has demonstrated a superior ability to release simulated stone fragments when compared to both standard and multi-wire nitinol stone extraction baskets."

In the U.S. each year, more than 1 million people are diagnosed to have kidney stones, with an estimated 10% of Americans destined to suffer them at some point in their lives, typically between the ages of 20 and 40. Although there are many treatments and surgical options for kidney stones, devices have been limited in their ability to capture small stone fragments which frequently result in secondary procedures.

The NGage has demonstrated a superior ability to securely capture and release kidney stones throughout the urinary tract, even in the most challenging locations," French said.