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J.C. Hardin, DVM
''Blocked'cats require several days or more of hospital care. Transfer of your cat to
your daytime doctor's office is an option the next day that they are open.
Otherwise, hospitalization should continue here until your cat is urinating voluntarily
with no problems.
A common cause of urethral obstruction is crystal accumulation Cats often
accumulate crystals in their urinary bladders. Male cats have more
trouble than females passing these crystals. Crystal accumulation in the bladder
leads to a blockage, preventing the cat from being able to urinate. This soon leads to
a life-threatening emergency as waste products and potassium build up in the
bloodstream because they can't be eliminated normally. Such elevations in
potassium can cause the heart to stop. The first order of business with these cats is
to get potassium levels back to normal. Emptying the bladder via cystocentesis
(needle and syringe) is usually attempted with the patient awake, or immediately
after anesthesia (as many cats are too upset and/or painful to allow this procedure
without anesthesia). Alternatively, many veterinarians choose not to empty the
bladder this way, but to place a urinary catheter as quickly as possible immediately
after anesthesia. If a catheter cannot be placed quickly however, cystocentesis is
usually performed. There is always some risk of bladder rupture during
cystocentesis, which is proportional to how long the bladder has been distended.
Likewise, there is always some risk in anesthesia.
There is increased risk of anesthetizing any blocked cat due to these high potassium
levels which can stop the heart while the patient is asleep. Blocked cats sometimes
do not survive the anesthesia, but this risk must be undertaken as anesthesia is
necessary to help them. Initially, the heart rate of blocked cats is very high, due
mostly to the effect of adrenaline from the pain and stress of being unable to urinate.
When the adrenaline's effect on the heart is relieved, the effect of the high
potassium takes over, which interferes with the electrical activity of the heart which
can make it stop. Calcium gluconate given slowly IV can help protect the heart from
the effects of high potassium.
Emptying the bladder quickly (either with the patient awake or asleep) allows the
kidneys to resume eliminating waste again, which helps correct the high potassium
levels, decreases other blood waste products, and relieves pain. IV fluids are
necessary as well. Often, dextrose (sugar) and insulin are given to help hasten the
correction of the high potassium levels. Calcium gluconate may be given to help
protect the heart from the high potassium levels. Usually, all the above emergency
procedures are performed before an initial blood panel (to tell us the potassium and
waste levels) can be run.
Sometimes cats are awakened immediately after the bladder is initially emptied and
IV fluids started, before the obstruction is relieved. A few hours later, potassium
levels have usually decreased significantly and it is safer to anesthetize for a longer
period of time needed to place a urinary catheter. Placing a urinary catheter in a
blocked male cat often takes a long time, as the crystal concentration usually must
be painstakingly cleared little by little. A polypropylene catheter is usually used
(several are often ruined in the attempt) for initial catheterization. The bladder is then
emptied again and flushed repeatedly to help clear as much remaining crystal
sludge as possible. Afterwards, if possible, the stiff polypropylene catheter is
removed and a soft red rubber catheter is placed and sutured in. An Elizabethan
(lampshade) collar is then placed to help prevent the cat from pulling out the
Rarely it is discovered that the obstruction was actually not due to crystals at all, but
is a plug of keratin (skin protein). These cats usually do not need to be catheterized,
and recover much more quickly. Stress and autoimmune disease have been linked
to urinary tract problems in cats, including blockage. Sometimes long term
medications or environmental changes to reduce anxiety are needed to resolve a
cat's urinary problems.
The urinary and IV catheters are left in usually for about 48 hours, after which the
urinary catheter is removed to see if the patient can urinate voluntarily again. At this
point, medications are sometimes needed to help relieve spasms or inflammation
associated with the trauma of being blocked and catheterized. Antibiotics are often
used during hospitalization and after to control or prevent urinary tract infections.
Patients need to be catheterized a second time if they can't urinate after the catheter
is removed. The total length of hospitalization may be quite long as all the
complications are managed and corrected. Patience is often required.
Urine tests help show what type of crystal was to blame for the blockage. A special
diet is usually prescribed to help decrease further crystal formation. A urine culture is
often recommended to pick an antibiotic that will best address any infection present.
X-rays of the bladder are usually advised to be sure no stones are present in the
bladder which would require surgery to remove.
Other problems can be apparent after the blockage has been relieved. Phenomena
called "post-obstructive diuresis" and "medullary washout" can occur. Simplified,
these are side effects of being blocked that lead to the kidneys no longer being able
to concentrate urine as well. Very large volumes of urine are excreted, requiring
very large volumes of fluid (with some potassium) to be taken in to prevent
dehydration. IV fluids need to be continued until the problem corrects itself. Another
less common side effect is 'detrusor atony' in which the the bladder has stretched
too much for too long, it loses its ability to contract. Manual bladder expressions and
medications such as bethanechol can help with this.
Bladder atony, or 'detrusor hyporeflexia', can also occur when a bladder has been
overdistended for too long. The bladder's 'tight junctions' are overstretched, and the
bladder cannot contract to expel urine. Medication such as bethanechol may be
helpful with this. This effect is usually temporary.
For cats who cannot be unblocked, who block repeatedly, or whose urethras are
scarred or torn from blockage, surgery is usually needed. This surgery 'reroutes the
plumbing' making the urethra shorter and wider like a female urethra, making it
harder for crystals and other debris to get trapped. This is called a "perineal
urethrostomy" or PU surgery. Post operative complications can include frequent
bladder infections, short term (a week or so) intermittent bleeding post op when
urinating, or stricture formation requiring a second surgery. A "prepubic
urocystostomy" is sometimes performed if a PU cannot be performed. With this
surgery, an opening is made in the abdomen connecting directly with the urinary
bladder. Patients must have their abdomens cleaned very frequently to prevent
urine scald in the skin. Bladder infections are more likely after this surgery as well.