A Novel Biopsying Forceps for Narrow Conduits in the Human Body

Introduction: Narrow conduits in the human body pose significant challenges in regards to obtaining tissue for various diagnostic tests and analyses. Bile ducts are such narrow conduits that transport bile from liver to the small bowel. The histology of tissues obtained at biopsy is the gold standard for diagnosis of several conditions of the bile ducts, including cancer. The current biopsy forceps, however, can only take biopsies of tissues that are directly in front of the forceps. The relatively small diameter (approximately 6mm) of the bile ducts in reference to the biopsy forceps means that most surface area of the bile ducts is parallel to the forceps, not in front of the forceps. This limitation results in inability to sample a significant surface area of the bile ducts, potentially leading to missing important diagnoses. In the case of bile duct cancer, late diagnosis, performed when the cancer has progressed beyond the bile ducts, results in survival rates as low as 2% (according to the American Cancer Society). Here, we report the development and testing of a novel biopsy device that collects tissue from the walls of the bile duct from locations transverse to the duct, thus increasing the sites available for biopsy.

Materials and

Methods: The new biopsy device has a 4 lumen tube (Fig. 1). Three centimeters from the distal tip, a window was cut through the tube wall into the main lumen (Fig. 1a and b). This is the window through which tissue will be suctioned into the tube and cut. Within this window, two smaller windows were cut into the vacuum channel (Fig. 1a). When suction is applied to the vacuum channel, tissue will be suctioned towards the inside of the main channel. Tissue that is now inside the main channel, will be cut by a sharp blade that is located inside the main lumen, distal to the main window (Fig. 1c) . The operation of the device is as follows: once the device is within the bile duct at the desired location, suction is applied using a vacuum pump. The vacuum will be applied through the 2 small windows cut into the vacuum channel, suctioning adjacent tissue into the tube. Once the tissue is in the main channel, the user actuates a handle to pull on a string which in turn pulls down the sharp blade, cutting the tissue (Fig. 2). The tissue that was cut is now retained inside the blade, ready to be manually extracted. The device went through a series of examinations, including gross examination of the specimen collected, H&E staining of the specimen collected, and testing the maneuverability and navigation of the device within a plastic bile duct model (Fig. 3).

Results, Conclusions, and Discussions: A model of bile ducts was constructed from porcine stomach and flexible rubber tubing and utilized throughout testing of the device. We tested the ability to suction tissue, proficiency of the cutting mechanism, and ease of utilization. Following initial testing, multiple improvements were made, as follows: a sharper blade, better blade-to-string connection, optimized vacuum ports, and an optimized main window for forming a vacuum seal with the tissue. An additional bile duct model was used to test the maneuverability of the device and its ability to navigate using a scope. We found that when vacuum was applied, tissue was suctioned into the main channel approximately 90% of the times tested. Once the tissue was in the main channel, the blade on the final iteration was able to cut the tissue 100% of the time. The device was proficient at navigation and displayed excellent maneuverability, as the user was able to reach the desired location with a success rate of approximately 80% on their first try, using a plastic bile duct model (Fig. 3). The user was able to use all the functions of the scope, precisely placing the device at the desired location. The device was able to collect specimens in locations parallel and to the side of the forceps. One of the specimens collected by the final iteration of the device was 6mm in length and 1mm in diameter. The H&E staining performed on the tissue collected confirmed its maintained architecture and suitability for pathologic examination (Fig. 4a and b).

The location of biopsy (on the side of the wall, parallel to the tube) is essential to the success of the biopsy procedures since the bodily conduits where this device is useful are very narrow and do not allow sufficient space for head-on taking of the biopsy.

Further studies are necessary to demonstrate the increased in vivo sensitivity for cancer diagnosis. In addition, this new biopsy device can easily be adapted to other narrow conduits in the human body, such as smaller airways, or urinary passages (urethra, ureters).

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