An anti-reflux valve developed to help esophageal cancer patients also has been shown to help those with bile duct obstruction, according to Kulwinder S. Dua, M.D., a research physician at the Medical College of Wisconsin in Milwaukee. The study, using the anti-reflux biliary stent in patients with cancer of the pancreas or bile duct, has been accepted for publication in the journal Gastrointestinal Endoscopy.
This bile duct stent with the "Dua Anti-Reflux Valve," named after its inventor, was cleared for use by FDA this year. The Dua stent, for short, has also been approved for use in Europe and Canada.
The bile duct carries bile from the liver to the intestines. When this duct is obstructed from cancers of the pancreas, gallbladder, or bile duct, bile begins to backup resulting in jaundice, itching, fever, chills, other organ malfunctions and death. About 30,000 new patients with pancreatic cancer and 4,000 new cases of bile duct cancer are diagnosed in the United States each year, most frequently in older people.
Surgery to remove the tumors is generally the best treatment, but often the disease has progressed too far to consider surgery. Consequently, a stent, a tiny, hollow tube, is inserted using a minimally invasive procedure to help improve the passage of bile. However, these stents frequently clog requiring repeat procedures to replace the clogged stents. The exact mechanism that leads to stent clogging is not known. There is a possibility that clogging occurs from contents from the intestines backflowing (refluxing) into the stent.
The "Dua Anti-Reflux Valve" was initially developed to reduce reflux of stomach contents in patients with cancers of the esophagus. The U.S. Food and Drug Administration cleared the "Dua Esophageal Stent" for use by patients with esophageal cancer in 2002. Using a similar windsock design, Dr. Dua modified the valve and attached it to the bile duct stent.
Laboratory studies to evaluate the flow dynamics of this modified stent showed that its valve was effective in reducing backflow while maintaining its primary function, namely forward flow. Results of these studies have also been accepted in Gastrointestinal Endoscopy.
Dr. D.N. Reddy from the Asian Institute of Gastroenterology in Hyderabad, India, conducted a study on 60 consecutive patients in whom the bile duct was obstructed from cancer of the pancreas or the bile duct. He placed a standard biliary stent in 30 patients and the Dua stent in the remaining 30 patients. The study showed that the Dua stent remained open for a longer time compared to the standard stent. This resulted in fewer repeat endoscopies for stent changes in patients with the Dua stent.
"That means a "better quality of life for these cancer patients," says Dr. Dua. Addition of the anti-reflux valve on the Dua stent did not compromise the main function of the stent, i.e. bile drainage as both stents were equally effective in improving liver tests, and complication rates were similar.
"Our next step is to do electron microscopic analysis of clogged standard and anti-reflux stents to evaluate the role of reflux of intestinal contents in stent clogging," Dua says. "We also hope to look at other uses for this type of stent."
Dr. Dua is associate professor of medicine at the Medical College and co-director of the Froedtert & Medical College GI Diagnostic and Therapeutic Laboratory. He is also the director of the Pancreatico-biliary Center at Froedtert, and chief of gastroenterology at the VA Medical Center, both major teaching affiliates of the Medical College. He is a member of the Cancer Center and Digestive Disease Center at the Medical College.
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