Pig skin heals forgotten patients
A decade ago, mortality rates for patients with enterocutaneous fistulas could reach 60 percent or higher. Now, a better understanding of how to manage complications such as malnutrition and electrolyte imbalances and the use of TNF blockers to induce closure have reduced both morbidity and mortality. Even so, patients who have complex fistulas involving multiple loops of intestine and significant involvement of the abdominal wall may not receive the surgical management they require and too often are left to cope on their own.
For these patients, physical and emotional suffering is often severe, says Robert R. Cima, M.D., of Mayo Clinic in Minnesota. Housebound, unable to work or eat, some try to manage the wounds themselves or shoulder the costs of home nursing care. Dr. Cima recounts the story of a young woman in her 20s who hadn't left her home in five years, noting that stories such as hers, although surprisingly common, aren't well-known. "This is not something people talk about," he says.
Most enterocutaneous fistulas result from complications of abdominal surgery, especially anastomatic leaks or iatrogenic bowel injuries. But 15 to 25 percent occur in people with inflammatory bowel disease (IBD), and in that setting, fistulas are even more problematic. Because the underlying disease and various anatomic factors make spontaneous closure unlikely, most patients with IBD are referred for surgery, even though several factors increase surgical complexity and risks.
Many patients with IBD have a history of multiple abdominal operations, including previous attempts to close the fistula, resulting in abdominal wall defects and poor tissue quality. Ventral hernias also are common, making closure of the abdominal wall difficult without resorting to flaps reinforced with prosthetic mesh. Yet mesh can cause serious complications if used in a contaminated field.
Biologic tissue grafts
New biomaterials, including porcine xenografts, may solve some of these problems. Created to replace host skin grafts, biologic tissue grafts can be either xenogenic or allogenic. Xenogenic tissue, created from pig intestine, is easily available and less expensive and ethically problematic than is cadaver skin.
Xenogenic biologics are rendered acellular through various forms of processing but retain the composition of the mammalian extracellular matrix, which acts as a scaffold for the migration and growth of host cells. Sterilized and treated to prevent immunoreactivity, porcine grafts may actually stimulate a robust immune response after implantation. And they are safe for use in infected fields, making them acceptable for abdominal wall reconstruction in patients with IBD.
Dr. Cima explains, "In cases where we would once use a skin graft, we now use these new materials to avoid that. The majority of patients can undergo surgical resection of the fistula and abdominal wall and reconstruction of the wall in a single procedure without the need to transfer skin or muscle to the site."
When that isn't possible or advisable, the xenograft is used as a temporary closure. In most cases, Dr. Cima says the porcine skin works so well that 50 to 80 percent of patients don't require plastic surgery.
"We end with a very reasonable result, which is huge for some of these patients," he says. "It changes their lives. They can get out of the house, return to work and become healthy, so we can start treating the underlying disease." He adds that the operation is successful in patients of all ages, including older adults. Depending on the complexity of the fistula, nutritional status and other factors, patients may stay in the hospital three days to two weeks after surgery.
Multidisciplinary team is key
Over the past five years, Mayo Clinic has become a leading referral center for IBD patients with refractory enterocutaneous fistulas. Dr. Cima notes that these patients require the expertise of a large and experienced multidisciplinary team.
"They need to be assessed and treated by gastroeneterologists, radiologists, surgeons, nutritionists, wound, ostomy and incontinence nurses — a private practice provider simply can't do it," Dr. Cima says. "It's a huge team effort."
Also huge, he says, is the market for biologics. "They're exorbitantly expensive, but so far they're the only products we can use for these patients. And that's critical because biologics work incredibly well and give us the flexibility to take on patients who used to get left behind."