Urethral Obstruction in Cats

By Kate O’Hara, DVM
angell.org/generalmedicine
generalmedicine@angell.org
617-522-7282

Urethral Obstruction (UO) is a life-threatening blockage of the lower portion of the urinary tract.  It prevents an animal from being able to urinate and, unfortunately, occurs relatively commonly in cats.  Although UO can occur in any cat, it is more prevalent in young to middle age male cats.  Male cats are more vulnerable to UO in part because their urethra (the portion of the urinary tract connecting the bladder to the outside world) is longer and narrower than in females.  Overweight cats, and cats that eat dry food only may also be at somewhat higher risk.

Urethral obstruction can have a number of different causes.  These include physical obstructions such as urethral plugs, urinary stones, strictures, or tumors.  Mechanical blockages can also occur secondary to urethral spasm or swelling secondary to inflammation in the lower urinary tract.  One common condition in cats that can lead to inflammation in the bladder and secondary obstruction is Idiopathic Feline Lower Urinary Tract Disease, or Feline Idiopathic Cystitis.

A complete urethral obstruction causes a “back-up” of urine which can damage the lower urinary tract and cause kidney failure.  This leads to an accumulation of toxins in the bloodstream and electrolyte imbalances that can be life-threatening.  Without help, UO can lead a cat to become critically ill within a short period of time, so it is important for owners to recognize this condition early.

Unfortunately, signs of urethral obstruction may not be recognizable to many pet owners until the condition is quite advanced and the cat is quite obviously sick.  Early signs of a developing UO include increased vocalization and frequent trips to the litter box.  Owners may also see cats licking more at their hind ends or straining unproductively in the litterbox.  These signs are not specific to UO and may be misinterpreted by owners who think their cat may have a less emergent condition such as a urinary tract infection, cystitis, or even constipation which can look similar.  This misinterpretation may cause owners to think that the situation is less critical than it is and lead them to delay seeking veterinary attention.  If left untreated for 24 hours or more, a cat can rapidly deteriorate and will begin to show other signs of systemic illness.  In these cases, cats may exhibit vomiting, lethargy, dull mentation, or inability to stand up.  These cats must be treated urgently and are at risk of dying.  Because of the seriousness of UO and its rapid progression, any cat that is straining in the litterbox should be brought to a veterinarian for evaluation.

The veterinarian will examine the cat and feel for a large firm, sometimes painful, bladder which cannot be expressed.  Some cats may still have a small urinary bladder if there is only a partial obstruction or if it is only in the early stages of developing a UO. Medical management might be attempted in these cats to try to prevent progression to a full blockage.  This management includes giving fluids under the skin for hydration and to keep the urine flowing, pain medication, and medication to prevent urethral spasms.  These medications will help keep the cat comfortable and may relax the urethra allowing urine to flow more readily.  Cats treated in this way may improve, but they are still at a high risk for developing a complete UO and will need to be monitored closely.  If a cat is found to have a complete UO, it will need to be admitted to the hospital to be stabilized and to have the obstruction physically relieved.  Your veterinarian will also want to submit additional diagnostic testing to assess how severely the cat is affected as well as to possibly determine an underlying cause.  These diagnostics include blood and urine testing as well as imaging of the urinary tract with either x-rays or ultrasound.

After a cat is admitted to the hospital, it will need to be stabilized with intravenous fluids and, in some cases, may also need additional medications to help correct life-threatening electrolyte imbalances.  The most important treatment, though, is relieving the urinary blockage.  This is most often accomplished through placement of a urinary catheter under sedation or anesthesia.  Occasionally, if an obstruction cannot be relieved in this way, a surgical procedure called a perineal urethrostomy (PU) may be needed to widen the outflow tract of the cat more permanently.

Once the urinary catheter is inserted into the bladder, the bladder is emptied and flushed to remove any inflammatory or crystalline material.  An indwelling urinary catheter will typically be kept in place for 24-72 hours while the cat is in the hospital.  During this time, urine production is closely monitored and intravenous fluids are used to help support the cat and improve the kidney values.  Again, pain medications and medications to relax the urethra are used.  If an underlying cause such as infection or urinary stones is identified then that will also have to be treated.  Once the cat has clinically improved (i.e. electrolytes, kidney values, and urine production have normalized), the urinary catheter is removed, and the cat will need to be monitored closely to ensure that it can now urinate on its own.  If re-obstruction occurs, the urinary catheter will need to be replaced.  If the cat begins to urinate, then it will be able to go home to continue its recovery.  A cat may continue to strain to urinate a bit for a couple days after hospitalization as the inflammation continues to resolve, but owners should make sure that the cat continues to pass urine, even if only in small amounts.

Unfortunately, cats that have had one urethral obstruction, are at risk for recurrence, so preventative measures are needed at home.  A prescription urinary diet is often advised to prevent the formation of urinary crystals or stones and to encourage water intake.  Keeping the cat well hydrated is essential so feeding canned food, providing fresh water daily, and encouraging water intake by adding extra water to food or providing a circulating water bowl is also recommended.  Additional management for Idiopathic Feline Lower Urinary Tract Disease focusing on reducing stress factors for the cat will also need to be instituted.

Cats that develop repeated urethral obstructions despite appropriate management changes, may benefit from perineal urethrostomy (PU) surgery as a more permanent solution.  This procedure involves the surgical removal of the narrow end of the urethra and may make obstruction less likely.

Urinary obstruction is, unfortunately, relatively common and is reported in 28-58% of all cats with lower urinary tract disease.  It is important to recognize the early signs, as delay in treatment can prove fatal.  Following preventative measures can significantly lower the risk of recurrence but it is important to remember that a cat with prior blockage will be more likely to block again and will need to be monitored throughout its life.