A “blocked Tom,” as they are referred to by those of us in the profession, is a cat, typically a male one, whose urethra, the tube designed to carry urine from the bladder out of the body, has become obstructed.
The cat is physically unable to urinate or can only pass very small quantities of urine at a time. The blockage usually is comprised of a plug of solid waste, such as mucous or crystals composed of minerals.
Sometimes the blockage is a bladder stone, which instantly complicates the situation, because most of these cats need surgery to remove other stones that are likely still in the bladder, once the obstruction has been relieved.
A urinary obstruction is probably the most serious, nontraumatic emergency a young, otherwise healthy cat could face. Depending on the owner’s level of suspicion that something is wrong, the cat may have gone many hours without being able to empty its bladder. This can lead to life-threatening electrolyte abnormalities as well as kidney damage. Luckily, these are typically reversible if the obstruction is relieved and corrective treatment is instituted, usually in the form of fluid therapy. Cats that are allowed to urinate outside are, by definition, more discrete about their bathroom habits. Many people like this aspect of cat ownership, but not seeing what your cat leaves behind means you don’t see changes in the volume of urine produced, or blood, which frequently accompanies developing urinary blockages.
Cats with a blocked urethra have a distended and extremely uncomfortable abdomen. They are often vocal about the pain, especially while trying to urinate. They become withdrawn, stop eating, and may vomit if kidney damage has occurred.
Veterinarians differ on how to approach urinary blockages. Some relieve the pressure on the bladder immediately by passing a needle into the abdomen and emptying a sufficient quantity of urine to bring some immediate relief. Once this is done, some routine blood work can tell us the electrolyte status and kidney function of the patient, an intravenous catheter placed, and fluid therapy started.
My belief is that doing this first renders the patient more stable for the anesthesia which must accompany the actual unblocking, but some vets feel that passing a needle into an extremely swollen bladder can bring on rupture of said bladder. Both approaches can be argued and defended.
Once the patient is under anesthesia, a urinary catheter specially-made for this purpose is passed up the urethra and into the bladder. This is often easier said than done, since the obstruction is most commonly at the very narrow tip of the penis, the opening of which is only about 1 to 2 millimeters in diameter.
With a urinary catheter in place, the bladder can be repeatedly flushed with sterile saline. This removes the small particles of solids in the bladder that contributed to the blockage, and gives the cat a patent urethra. The catheter is usually left in place for 24 to 48 hours. At-home care typically involves feeding a diet that encourages more water consumption, so that the urine is more dilute and less prone to solid formation.
Christie Long is a veterinarian at the VCA Fort Collins Animal Hospital. Call her at (970) 204-4567 or send email to email@example.com.