William R. Pritchard Veterinary Medical Teaching Hospital

Benign Obstructions

Tracheal Collapse

Nasopharyngeal Stenosis

Ureteral Obstruction

Urethral (Benign) Obstruction

Esophageal Obstruction

Tracheal Collapse

Photo: Video Poster

Select image to view video

The trachea is a flexible tube in the neck and chest that allows passage of air down to the lungs during breathing. When the trachea loses rigidity, it can close down or "collapse" and prevent air movement to the lungs. This is often manifested by a "honking" cough, and signs such as blue gums and falling over may occur. Tracheal collapse is often worsened by conditions that cause your pet to become excited such as stress or exercise, hot weather, and eating or drinking. After the diagnosis has been confirmed, management with oral medications and weight control are generally recommended, but these may not always be successful. Surgery can be a treatment option for some pets with tracheal collapse; however, this is not recommended in all cases.

For dogs with tracheal collapse that is refractory to medical management, tracheal stenting may need to be considered; however, it is important to remember that not all cases are reasonable candidates for tracheal stenting. Tracheal stenting involves the placement of a tube-like structure (ie. stent) into the trachea to push the walls of the trachea outward to allow for air passage. This procedure involves general anesthesia, but is generally very quick and easy to perform. Some immediate relief is expected, however, long-term medications may still be required to control signs.

Veterinarians - Click here for more information

Background Information
Stent placement is indicated as a last resort for management of cough and/or respiratory distress associated with intrathoracic tracheal collapse. For dogs with cervical collapse alone, placement of extraluminal rings remains the primary recommendation. Stenting should be considered as a salvage procedure for dogs that have failed all attempts at aggressive medical management including weight control. Little information is available on the use of stents in young dogs or in dogs with bronchial or generalized airway collapse. Most of the dogs that we see at the VMTH have bronchial collapse with or without tracheal collapse, and therefore, complete diagnostic evaluation is recommended prior to deciding on the use of stents in affected animals.

Tracheal stent placement is best considered as a 2-step procedure. Firstly, overall health status must be determined, followed by a complete assessment of the respiratory tract. Special attention must be paid to the length and location of airway collapse and the presence of concurrent upper or lower airway disease. Upper airway disease and infectious or inflammatory lower airway disease should be treated prior to stent placement. Appropriate case selection is critical – the dog should be lean and very tractable to allow appropriate post-operative management.

Diagnostic and Treatment Steps at UC Davis

At the first examination, the following will be obtained:

  1. Physical examination
  2. Minimum database
  3. Neck and chest radiographs
  4. Fluoroscopy to determine the length of tracheal collapse
  5. Anesthesia for airway assessment:
    • Upper airway examination
    • Full lower airway examination by bronchoscopy
    • Bronchoalveolar lavage with cytology and culture
  6. Tracheal measurements

At this stage, the appropriate size for a stent must be calculated from the fluoroscopic images. Obtaining the proper size for the stent is critical for success. In some cases, placement of the stent requires a second anesthesia and can be done with bronchoscopy or fluoroscopy. Post-procedure radiographs are needed. Appropriate post-operative care is critical to success and includes heavy sedation, cough suppressants, steroids, and antibiotics. Oxygen therapy may be needed in some cases. The dog generally is discharged on 3-6 weeks of a tapering dose of steroids, antibiotics, and cough suppressants.

If a dog has severe respiratory distress associated with tracheal collapse and it cannot be extubated or recovered from anesthesia, a stent can be placed on an emergency basis.

While stents can successfully control debilitating signs associated with intrathoracic tracheal collapse, they are not without risk. Complications of stent placement include collapse, migration, stricture formation, and airway rupture. Follow-up examination with radiographs is required within 1 month, and repeat bronchoscopy should be performed after 4-6 months to detect any problems. Owners must be aware that cough may persist after stent placement.


Nasopharyngeal Stenosis

Photo: Video Poster

Select image to view video

The nasopharynx is the junction between the back of the nasal passages (region traditionally considered the nose or "muzzle") and the region where the esophagus and trachea begin. When air is breathed in through the nose, it travels through the nasal passages, through the nasopharynx and enters the trachea to be passed to the lungs. Obstruction in this region (stenosis) results in poor or no airflow, which prevents oxygen from being carried to the trachea effectively when the pet's mouth is not open. Signs commonly seen with this condition are sneezing, nasal discharge, constant open-mouth breathing and snoring. Animals may be unable to sleep, eat, or breathe normally unless the mouth is open.

Stents can be placed across the obstruction to permanently open the stenotic area. When stents are in position, air can pass through the nostrils, through the nasopharynx and down to the lungs. This procedure requires general anesthesia and specialized equipment such as computed tomography, fluoroscopy and rhinoscopy. If the stenotic region can be opened sufficiently, an improvement in the clinical signs demonstrated by your pet is expected.

Veterinarians - Click here for more information

Background Information
Nasopharygneal stenosis occurs when the nasopharynx becomes narrowed, and clinical signs generally manifest as difficulty breathing when the mouth is not open, nasal discharge, sneezing and inspiratory stertor. Several causes have been proposed and both congenital and acquired conditions have been documented; however, the majority of cases are thought to be secondary to an inflammatory condition within the nasopharynx. (Mitten 1988, Glaus 2005, Berent 2008)

Historically, treatment of nasopharyngeal stenosis has consisted of balloon dilation, but cases that become refractory or have severely thickened tissue often require a more permanent option. Nasopharyngeal stenting has arisen as an option in these cases. Utilizing fluoroscopic- and rhinoscopic-guidance, a balloon-expandable stent is positioned across the stenosis and dilated. A recent case series describes this procedure in 6 cases. (Berent 2008) In those cases, all animals had resolution of clinical signs after the stent was placed. Additionally, 5/6 were breathing normally at a follow-up time interval of 12-28 months after the procedure. (Berent 2008)

Diagnostic and Treatment Steps at UC Davis
Dogs and cats with suspected upper airway obstruction will likely have several initial diagnostics tests performed at UC Davis including bloodwork (CBC/chemistry panel), chest radiographs, sedated or anesthetized oral examination, rhinoscopy and potentially tracheobronchoscopy. Further diagnostics may include CT scan of the head. After these preliminary diagnostics, if nasopharyngeal stenosis is suspected, rhinoscopy coupled with fluoroscopy may need to be performed for balloon and stent sizing. If the case is deemed a candidate, the procedure is performed under general anesthesia with fluoroscopic- and rhinoscopic-guidance to properly place the stent. Patients are usually monitored in the hospital for a few days after the procedure, and future CT, rhinoscopic, and/or fluoroscopic evaluation may be necessary.


Berent AC, Weisse C, Todd K, et al. Use of a balloon-expandable metallic stent for treatment of nasopharyngeal stenosis in dogs and cats: six cases (2005-2007). JAVMA 233:1432-1440.

Glaus TM, Gerber B, Tomsa K, et al. Reproducible and long-lasting success of balloon dilation of nasopharyngeal stenosis in cats. Vet Record 2005;157:275-259.

Mitten RW. Nasopharyngeal stenosis in four cats. J Small Anim Pract 1988;29:341-345. Boswood A, Lamb CR, Brockman DJ, et al. Balloon dilatation of nasopharyngeal stenosis in a cat. Vet Radiol Ultrasound 2003;44:53-55.


Ureteral Obstruction

Photo: Ureteral Stent/Bypass Radiographs

Select image for
larger image

Dogs and cats have two ureters. The ureter is the tube connecting the kidney to the bladder and has the responsibility of carrying urine to the bladder after it is formed in the kidney. The ureter can become obstructed by crystals, stones, blood or a combination of these substances. Obstruction can prevent urine from travelling to the bladder which may be a life-threatening condition. Depending on the type of obstruction, surgery may be indicated. Surgery can be successful in many cases, however, surgery is not without complications and may not be indicated in select situations.

Other options for the treatment of ureteral obstructions include ureteral stenting and subcutaneous ureteral bypass. Ureteral stenting involves the placement of a tube within the ureter that extends from the kidney to the bladder to allow for the passage of urine. In ureteral obstructions that occur in dogs, the stent can often be placed with a minimally invasive technique involving the use of a camera that is passed into the bladder. In cats, ureteral stents are placed with a surigical procedure. Subcutaneous ureteral bypass is a procedure where an artificial ureter is created with several tubes. These tubes are designed to allow urine to pass from the kidney to the bladder providing a bypass of the ureter.

Veterinarians - Click here for more information

Background Information
Ureteral obstructions are a complex problem affecting both dogs and cats. Surgery is generally recommended for cases of single, obstructive ureteral calculi. One study suggested that most cases of proximal ureteral obstruction are treated by ureterotomy whereas most cases of distal ureteral obstruction are treated by partial ureterectomy or ureteroneocystostomy. (Kyles 2005) However, cases of ureteral obstruction are often not straight-forward, as some stones may not be noted on radiographs or ultrasound, and some dogs and cats may have multiple stones or simply an accumulation of crystals resulting in ureteral obstruction.

Reports of the treatment of ureteral disease are uncommon, but some recent studies have evaluated the outcomes in cats with ureteral calculi. (Kyles 2005, Kyles 2005) The postoperative complication rate in one series of cats was 31%, with urine leakage and persistent ureteral obstruction being the most common complications reported. (Kyles 2005) Mortality rate has been reported as high as 18%. (Kyles 2005)

Ureteral stenting has been advocated as a means of allowing urine to pass from the kidney into the bladder in cases of obstruction. Ureteral stenting involves the placement of a tube within the ureter that is anchored both within the renal pelvis and the bladder. Ureteral stents are placed either surgically or with the assistance of cystoscopy; sometimes, these stents are removed in the future, but clinical status of the patient may alter this course. Over time, these stents cause passive dilation of the ureter around the stent, allowing urine and potentially calculi to pass. (Lennon 1997)

Studies of the use of ureteral stents and subcutaneous bypass techniques in companion animals are lacking, but the use of these techniques in humans shows promise. (Auge 2002) The indications for stents are not fully outlined, but urologists consider the use of ureteral stents in several situations. Stents have been placed to allow for passage of urine in a ureter that has been obstructed by a ureteral calculus. (Auge 2002) Additionally, some stones may pass alongside a stent that has been placed due to the passive dilation stimulated by stent insertion. (Lennon 1997) Stents may also be considered after surgery of the ureter or ureterovesicular junction has been performed. (Auge 2002) Lastly, obstruction of the ureter secondary to neoplasia may be relieved by stent placement. (Liatsikos 2009)

Diagnostic and Treatment Steps at UC Davis

Most cases that are considered for ureteral stenting or subcutaneous ureteral bypass will require basic bloodwork (CBC/chemistry panel), abdominal radiographs, abdominal ultrasound, chest radiographs and possibly cystourethroscopy (dogs). Depending on the size of the patient and the type of disease being treated, ureteral stenting may be performed with cystoscopy alone or may require surgical placement of the ureteral stent. Subcutaneous ureteral bypass requires a surgical approach.


Auge BK, Preminger GM. Ureteral stents and their use in endourology. Current Opinion in Urology 2002;12:217.

Kyles AE, Hardie EM, Wooden BG, et al. Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi: 163 cases (1984-2002). JAVMA 2005;226:932.

Kyles AE, Hardie EM, Wooden BG, et al. Management and outcome of cats with ureteral calculi: 153 cases (1984-2002). JAVMA 2005;226:937.

Lennon GM, Thornhill JA, Grainger R, et al. Double pigtail ureteric stent versus percutaneous nephrostomy: effects on stone transit and ureteric motility. European Urology 1997;31:24.

Liatsikos EN, Karnabaidis D, Katsanos K, et al. Ureteral metal stents: 10-year experience with malignant ureteral obstruction treatment. J Urology 2009:182:2613-2618.


Urethral Stricture/Non-malignant Obstruction

Urethral Stricture Benign Obstruction Ballooon

Photo: Video Poster

Select image to view video

Urethral Stricture Benign Obstruction Stent

Photo: Video Poster

Select image to view video

The urethra is the tube that carries urine from the bladder and expels it outside of the body. When trauma occurs to the urethra or surgery of the urethra is necessary, stricture (decrease in diameter or closing down) can occur. When a complete obstruction occurs, this is a life-threatening emergency, and the affected pet should be evaluated immediately. Opening of the stricture can be performed with a balloon device that causes expansion, but this may not be effective in all cases. 

If balloon dilation is unsuccessful, there may be an indication for the placement of a metal or metal-alloy stent that allows for opening of the urethra. The stent pushes outward (against the walls of the urethra) to allow opening of the urethra resulting in the improved ability to urinate. 

Tumors of the urethra are seen more commonly than trauma-induced strictures. Please see the page on “Malignant Obstruction” for more information.

Veterinarians - Click here for more information

Background Information
Urethral obstruction secondary to stricture or non-malignant disease (urethritis) is uncommon. However, similar to urethral obstruction secondary to neoplasia, this condition is life-threatening. Urethral trauma is likely the most common reason that strictures develop and causes of urethral trauma in dogs and cats includes motor vehicular accidents, gunshot wounds, urethral calculi, iatrogenic traumatic catheterization and surgery. (Anson 1987, Anderson 2006) Of 20 dogs in one study, 14 (70%) developed urethral rupture secondary to motor vehicular accidents; however, cats develop urethral trauma most commonly from traumatic catheterization and /or urethral calculi. (Anderson 2006)

Urethritis has been reported sparingly in the veterinary literature, but can manifest in polypoid form or result in severe thickening of the urethral wall thus causing urethral narrowing and obstruction. In a study evaluating infiltrative urethral disease, 24% of dogs developed nonneoplastic disease characterized as granulomatous urethritis. (Moroff 1991) Proliferative urethritis (without a granulomatous component) has also been reported. (Hostutler 2004)

Diagnostic and Treatment Steps at UC Davis
Initial diagnostics will include bloodwork (CBC/chemistry panel), chest radiographs, abdominal ultrasound, urinalysis, urine culture and cystourethroscopy. Biopsies will likely be obtained during cystourethroscopy, and stent measurements may be made during that time utilizing fluoroscopy. A balloon procedure may be considered, or stent placement could be indicated immediately. Serial evaluation of bloodwork, urinalysis and urine culture will likely be recommended. Cystourethroscopy may need to be performed at a future date to assess stent patency and further development of urethritis.


Anderson RB, Aronson LR, Drobatz KJ, et al. Prognostic factors for successful outcome following urethral rupture in dogs and cats. JAAHA 2006;42:136-146.

Anson LW. Urethral trauma and principles of urethral surgery. Compend Contin Educ Pract Vet 1987;9:981-988.

Hostutler RA, Chew DJ, Eaton KA, et al. Cystoscopic appearance of proliferative urethritis in 2 dogs before and after treatment. JVIM 2004;18:113-116.

Moroff SD, Brown BA, Matthiesen DT, et al. Infiltrative urethral disease in female dogs: 41 cases (1980-1987). JAVMA 1991;199:247-251.


Esophageal Obstruction

Esophageal Stricture Stent Placement

Photo: Video Poster

Select image to view video

The esophagus is the organ that carries food from the mouth to the stomach. The esophagus may become closed down due to trauma, previous surgery or chronic irritation from gastric juices. The decrease in esophageal diameter is called a stricture and may result in difficulty of the passage of food into the stomach. Several treatment options are available for esophageal strictures, and an internal medicine specialist can discuss and provide these options to pet owners. 

In certain rare cases of strictures that do not respond to traditional therapies, esophageal stenting may be considered. Esophageal stenting involves the placement of a metal or metal-alloy stent that has the capability of opening the esophagus. The purpose of the stent is to improve your pet’s ability to pass food down the esophagus, but other medical management techniques will likely continue to be necessary.

Veterinarians - Click here for more information

Background Information
The large majority of esophageal strictures are presumed to occur secondary to gastroesophageal reflux during anesthesia. (Leib 2001, Adamama 2002, Bissett 2009) Risk factors for the development of benign esophageal strictures include gender (females more likely than males), a recent history of anesthesia, having received an oral antibiotic and having a history of vomiting. (Bissett 2009) Clinical signs generally seen with esophageal strictures include regurgitation, gagging, weight loss, decreased appetite, pytalism, lip licking, and odynophagia. (Bissett 2009, Glazer 2008, Leib 2001)

Generally, initial treatment of benign esophageal strictures consists of progressive and serial dilation of the stricture with either esophageal bougienage or balloon dilation. In one study, outcomes in dogs and cats who underwent esophageal bougienage were considered good in 70% and 75% of cases, respectively. In a separate study, 88% of dogs and cats treated with balloon dilation were considered to have a successful outcome. (Leib 2001)

In cases refractory to either esophageal bougienage or balloon dilation, esophageal stenting may be considered. Esophageal stenting involves the placement of a dissolvable stent made of polydioxanone or a permanent stent that may or not be covered. The stents are often anchored with a suture either cranial or caudal to prevent migration.

Diagnostic and Treatment Steps at UC Davis

Initial diagnostics will include bloodwork (CBC/chemistry panel), chest radiographs, abdominal ultrasound, and esophagoscopy. Biopsies will likely be obtained during esophagoscopy. An esophagram will need to be performed to determine the appropriate stent size. After determining stent size, the stent is ordered and the stent is placed under anesthesia. A small surgical approach will need to be performed to place the permanent suture anchoring the stent to the esophagus.


Adamama-Moraitou KK, Rallis TS, Prassinos NN, et al. Benign esophageal stricture in the dog and cat: a retrospective study of 20 cases. Can J Vet Research 2002;66:55-59.

Bissett SA, Davis J, Subler K, et al. Risk factors and outcome of bougienage for treatment of benign esophageal strictures in dogs and cats: 28 cases (1995-2004). JAVMA 2009;235:844-850.

Glazer A, Walters P. Esophagitis and esophageal strictures. Comp Cont Educ Pract 2008;30:281-291.

Leib MS, Dinnel H, Ward DL, et al. Endoscopic balloon dilation of benign esophageal strictures in dogs and cats. JVIM 2001;15:547-552.