Interventional radiology in veterinary medicine: Now and in the future (Proceedings)
Interventional radiology involves the use of imaging modalities such as fluoroscopy or ultrasonography to gain access to different structures in order to deliver materials for therapeutic purposes. The use of interventional techniques in veterinary patients offers a number of advantages compared to more traditional therapies. These procedures are minimally invasive and can therefore lead to reduced perioperative morbidity and mortality, shorter anesthesia times and shorter hospital stays. Some techniques such as chemoembolization of tumors or palliative stenting for malignant obstructions offer alternative treatment options for patients with conditions that may not be amenable to standard therapies. There are not necessarily disadvantages for the patient as much as the provider, in the initial cost of equipment and time to gain expertise. Radiation exposure to personnel can be substantial when using fluoroscopic guidance and full lead gowns, thyroid shields, and leaded glasses are recommended and may add to the initial purchase price of equipment.
Small and toy breed dogs are predisposed to tracheal collapse due to cartilage degeneration. The trachea collapses dynamically during respiration. These patients can present with mild "honking" to respiratory distress due to complete airway obstruction. Aggressive medical management is the treatment of choice in these patients. Combinations of anti-inflammatories, cough suppressants, sedatives, bronchodilators, antibiotics, weight loss, restricted exercise, and removal of inhaled allergens (such as smoke) can help to control clinical signs. Treatment of concomitant diseases is imperative as well. Small airway disease, pulmonary parenchymal disease, heart disease, and brachycephalic airway syndrome exacerbate tracheal collapse and should be addressed. Patients that fail this aggressive management and concurrent diseases have been adequated treated can be candidates for interventional or surgical treatments. Extraluminal tracheal ring prostheses has a reported efficacy of 75-85% for extrathoracic tracheal collapse, but significant morbidity is associated with surgery. Complications such as laryngeal paralysis, perioperative death, and permanent tracheotomy can be seen. If significant intrathoracic tracheal collapse is present surgery can have even higher morbidity. Intraluminal self-expanding metallic nitinol stents have excellent flexibility and can now be placed in the trachea (both cervical and intrathoracic) to treat tracheal collapse using a minimally invasive procedure. Another advantage of tracheal stent placement versus surgery is the short anesthesia time, which is beneficial in geriatric patients with concurrent cardiac or pulmonary disease. It is important to realize that medications will still be required in a majority of patients following stent placement however. When used appropriately with careful patient selection, significant improvement in the quality of life can be achieved with stent placement in addition to medical management, with a lower morbidity than surgery. There have however been complications associated with intraluminal tracheal stent placement which include stent shortening, excessive granulation tissue, progressive tracheal collapse and stent fracture. In young patients, stents should be carefully considered as the life span of these stents has not been determined.