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Urethral stent placement

Possible causes for a urethral obstruction includes severe inflammation from an infection, granulomatous urethritis, cancer (more commonly transitional cell carcinoma), calculi (radiolucent and radiopaque), among others. Granulomatous urethritis is thought to be an immune-mediated disease. Interestingly, dogs with this disease commonly have a preceding history of urinary tract infection.

Fluoroscopic video of urethral obstruction

A cystoscopic evaluation is a minimally invasive way to determine the cause of a patient's inability to urinate. This will allow us evaluate the urethra and bladder as well as collect biopsies. Additionally, a contrast study will help determine the extent of the disease. Lastly, a urethral stent can be placed to relieve the mechanical obstruction and allow the patient to urinate again. Possible urethral stent consequences includes urinary incontinence, which occurs in approximately 47% of female dogs. However, severe incontinence only occurs in approximately 25% of dogs that undergo a urethral stent placement. Stranguria can also occur even after a urethral stent is placed. However, moderate to severe stranguria only occurs in 15% of female dogs.

Urethral stent deployment
Fluoroscopic video of urethra contrast flow post-stent placement

Granulomatous urethritis is a rare disease, so there isn't a lot of information available. However, it seems that it is associated with a good prognosis since many dogs respond well to treatment. Non-obstructed dogs are typically treated medically. However, this is not possible in dogs that are unable to urinate since it may take days to possibly weeks for an adequate response to occur. In this case, options includes the placement of a urethral stent, a cystotomy tube, or to maintain a long-term urinary catheter.

Transitional cell carcinoma is the most common cancer to cause a urethral obstruction. Unfortunately in the urethra, this cancer leads to obstruction and inability to urinate. The median survival time for dogs after the diagnosis of an obstructive carcinoma of the urethra that underwent a urethral stent placement was 108 days (7 to 1.226 days). These dogs had various combinations of treatment before and after the stent placement. The shortest survival was in dogs that only underwent the urethral stent placement, which was 48 days (7 to 484 days). The best survival was in dogs that received nonsteroidal anti-inflammatories for at least 4 weeks prior to urethral stent placement and chemotherapy after the stent placement, which was 315 days (8 to 536 days). Patients that did not receive nonsteroidal anti-inflammatories prior to stent placement, but chemotherapy afterwards had a median survival time of 60 days (8 to 251 days). It is important to mention that this was a small number of dogs and there is a lot of variability between patients. Nonetheless, the thought is that patients that do not die from inability to urinate (most common scenario) will likely die from the effects of the cancer itself (eg. spread of the cancer - metastasis).

Urethral obstruction can be severe enough where even a very thin (0.018) guidewire cannot be passed through the cancer, but you can still stent the patient

It was impossible to pass a guidewire through the prostatic carcinoma in the urethra. However, it was possible to maneuver a flexible cystoscope and therefore place a urethral stent to relieve the obstruction.  

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