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Collapsing Trachea

09/18/2009

A persistent cough that at times turned into an obnoxious hacking, honking clatter landed a Yorkshire Terrier named “Charlie” at the University of Pennsylvania Ryan Veterinary Hospital. The 6-year-old, 7-pound Yorkie had a collapsing trachea, a potentially life-threatening condition in which the windpipe collapses, cutting off airflow to and from the lungs.

The veterinary surgeon, Chick Weisse, V.M.D., DACVS, had performed surgery many times for the condition, which is common in toy breeds. In some veterinary circles the surgery was considered a last-resort option due to potential complications. Most dogs are first treated with steroid medications and cough suppressants, but Charlie was among the 15 to 30 percent that do not respond to medical treatment. Seeking an alternative, Weisse consulted Jeffrey Solomon, M.D., an interventional radiologist at the Hospital of the University of Pennsylvania. 

Solomon joined Weisse at the veterinary hospital and together they examined Charlie’s windpipe using fluoroscopy, an imaging technique that feeds a continuous X-ray beam through the body allowing doctors to view moving body structures from a monitor. While the tiny dog was under general anesthesia, they could see that he suffered from an extrathoracic collapse located outside the ribs, as well as intrathoracic and bronchial collapse. The good news is that a metallic stent could be inserted to hold open the trachea and treat the condition.

A rigid tube of tracheal rings made of cartilage, the trachea extends from the throat into the smaller branches of airways called bronchi, which then enter into the top of the lungs. Normally the tube is circular but when weakened, it flattens or collapses from top to bottom, cutting off a dog’s airflow. Though collapse can occur at any point along the windpipe, intrathoracic collapses that occur inside the lungs are more difficult to treat.

Besides Yorkies, affected breeds include Chihuahua, Pomeranian, Shih Tzu, Lhasa Apso, Maltese and Bichon Frise. The condition occurs either when the tracheal membrane is loose, causing obstruction, or when the cartilage is soft rather than hard. Allergens, excessive weight, high humidity and environmental stimulants like smoke, dust, stress and undue excitement are among the culprits leading to worsening collapsed trachea.

To measure the size of stent Charlie would need, the doctors used positive pressure ventilation. The stent was carefully passed into position through an endotracheal tube inserted before the procedure began. Watching on the monitor, the doctors threaded the stent down the windpipe inside a small catheter delivery system. The entire procedure was completed within 30 minutes, a fraction of the time required for traditional surgery, meaning a shorter anesthesia time. Better yet, the minimally invasive procedure had less risk of immediate post-surgical complications, and thus Charlie’s owner was able to take him home later that day.

The successful outcome of Charlie’s treatment for collapsing trachea in 2003 led Weisse to doing a fellowship in interventional radiology at the Hospital of the University of Pennsylvania. One day a week for a year, Weisse observed specialists treating human patients for occlusions in their blood vessels, obstructions of their kidneys, inappropriate bleeding, even some cancers, using minimally invasive techniques. Human doctors are the dinosaurs of interventional radiology, having first used angiography to study heart disease in the 1960s. Veterinary medicine, so far, had not tapped into contemporary imaging to such an extent as a means of diagnosing and treating conditions that fail to respond to conventional therapies.

Following the fellowship, Weisse began a dual appointment as assistant professor of surgery at Ryan Veterinary Hospital and assistant professor of radiology at the Hospital of the University of Pennsylvania. His work in interventional radiology at the veterinary hospital sparked the beginning of a service dedicated to using minimally invasive imaging modalities for better outcomes. For toy breeds, it meant alternatives to high-risk conventional treatments for conditions such as Charlie’s collapsing trachea but also for intrahepatic liver shunts and cancer that cannot be removed surgically or treated well with chemotherapy. Chemotherapeutic agents can be delivered through the artery, directly to tumor sites, particularly in the liver and bladder.

Two years after Weisse completed his fellowship in interventional radiology, another Univer­sity of Pennsylvania veterinarian pursued a fellowship in interventional endoscopy and interventional radiology working with Demetrius Bagley, M.D., a urologist at Thomas Jefferson University Hospital in Philadelphia, and Dr. Solomon at the University of Pennsylvania. Allyson Berent, D.V.M., DACVIM, trained in internal medicine and became focused on using an endoscope, a flexible tube with a lighted camera attached, to view the urinary tract, respiratory tract, digestive tract and other internal organs. The nonsurgical procedure allows doctors to see obstructions and ultimately provide less invasive options with fewer complications. 

“Not many good alternatives have been available for treating dogs,” Berent says. “Some surgeries are risky, and some that go well in humans simply don’t go well in dogs, and vice versa. Interventional endoscopy, which includes interventional radiology, opens new opportunities for treating these canine patients.”

Weisse and Berent recently took new positions at The Animal Medical Center in New York City. He is director of interventional radiology, and she is director of interventional endoscopy. Through their work, they aim to help patients and owners who before had limited choices. At referral clinics throughout Manhattan, they will help develop a veterinary specialty in its infancy. Metropolitan toy breed owners whose dogs are diagnosed with painful yet treatable conditions will benefit from avoiding open, high-risk surgeries. In the next few years, interventional radiology will likely become more common in treating dogs of all sizes.  

This article originally appeared in Today's Breeder, A Nestlé Purina Publication Dedicated to the Needs of Canine Enthusiasts

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