This is a life threatening emergency in cats that is most commonly seen in males, but can also occur in females.  If you notice ANY of the following signs in your cat he/she may be blocked or becoming blocked:

1 - your cat is in and out of the litterpan frequently

2 - urine spotting on furniture, you, the floor or urinating outside the litterpan

3 - straining to urinate and/or vocalizing when trying to do so

4 - producing small amounts or no urine when voiding

5 - blood in the urine or blood spots around the house

6 - excessive licking of the urogenital area

7 - vomiting, decreased appetite, lethargy, hiding

There are other conditions that can have similar symptoms including, but not limited to:

urinary tract infection, feline interstitial cystitis (FIC) - a stress driven inflammation in the bladder, and more, but for the moment we are focusing on obstruction or blockages....

What IS a "urethral obstruction"?

The urethra is a muscular tube that allows us to empty or void urine.  It connects the bladder to our outer opening.  In females this is a very short tube, in males it is longer and has greater risk of being blocked.  If this tube becomes blocked for any of the reasons below, urine will not be able to pass out of the bladder leading to the bladder becoming very full and stretched.  Urine is unable to pass from the kidneys.  Substances build up in the blood stream and the bladder is at risk of rupturing and the patient at risk of kidney failure and death from toxicity, electrolyte imbalances and from the bladder actually rupturing.  This is not something that your cat will 'get over on their own'.  It is a life threatening and urgent emergency!

Most commonly one of two things may happen, sometimes both...

1 - if there is a source of chronic inflammation that muscular tube (urethra) can become very irritated and may spasm, like a "charlie-horse" cramp - closing down and unable to relax so urine cannot pass out of the bladder.

2 - the presence of crystals in the urine is extremely irritating to the lining of the bladder and the urethra - acting like razor blades that cut and scrape the area.  These crystals may form a "plug" of crystals or a small  'stone' that blocks the outflow of urine from the bladder.  Some patients become blocked by mucous plugs that develop secondary to all of the irritation and inflammation in the urethra. 

Less commonly but still occurs:

1 - bladder stones may block the outflow of the bladder to the urethra. They may move at times acting like a "stop cock" and only temporarily block the outflow although if small enough they may become lodged in the urethra as described above.

2 - bladder tumors do occur in older cats although they are not common.  These may become large enough to block the flow of urine out of the baldder.

3 - neurogenic issues - damage to the nerves that control the emptying of the bladder can lead to patients being unable to void normally.

Not all obstructions are "total" - in some cases a bit of urine is still passing.  Any male cat with crystals present in the urine is at great risk of potentially becoming 'blocked" until those crystals are dissolved or passed out in the urine.  The treatment for these cases will be based on the individual patient and a discussion with your veterinarian.  Pain medication, muscle relaxants and if indicated, antibiotics, may be prescribed. All of these cats though will need to be on a veterinary diet to dissolve any struvite crystals that are present and to limit the further formation of struvite or calcium oxalate crystals.  It is important to realize that there is no grocery store or pet food store diet that will do this. 

Your veterinarian will want to perform a urinalysis and ideally take screening xrays for stones or other abnormalities.  Please be aware, crystals and stones may be present but may not be seen on the urinalysis, this is why screening xrays are very helpful. Mineralization in the kidneys, ureters and/or bladder may be seen on screening xrays.

Crystals will tend to 'settle' to the lowest point of the bladder and may not be floating freely in the urine when the sample is collected.  I have seen it happen before, to myself and to numerous other veterinarians who get one sample with no crystals present and then a later sample where they are present in large numbers. This is why your veterinarian will likely recommend the special diet for your cat even if crystals were not seen, especially if a male cat.  

With the development of antibiotic resistance it is very important to perform that urinalysis to ensure that if an infection is present antibiotics are dispensed versus dispensing them without having diagnosed the presence of an infection.  

There may be other important clues in that urine - high glucose indicating diabetes, low concentration that may indicate decreased kidney function, abnormal cells and more. 

If your cat did block or had crystals present you will need to watch your cat's total urine output over a 24 hour period closely for the next 3-6 weeks and should be monitoring on a daily basis long term to catch repeat occurrences early.  

What causes crystals in the urine?

The two types of crystals commonly seen in cat urine are struvites and calcium oxalates. There are others, but those are not often seen and if found in your cats' urine may indicate that additional diagnostics should be done to check organ function.  We can dissolve struvite crystals with a special diet and we can limit further struvite and calcium oxalate crystal formation with those same diets.  Calcium oxalate crystals will not dissolve though and have to be passed out in the urine.  Any cat with these present will be at risk of blocking until those crystals present are voided and no further ones are being formed. 

Diet is the main consideration although this can be an inherent issue to the individual - if your cat has made crystals in the urine once, they are at a much greater risk of doing so again, especially if they go back to a non-urinary formula.  Some breeds are more prone to making crystals than others.  High calcium diets can be a risk factor too - so this is something to consider if feeding a very high protein diet that has more bone present in it. 

The concentration of the urine, the pH of the urine and mineral substrate present are all factors in crystal formation and precipitation in the urine. This is why your veterinarian will advise trying to get your cat to eat the canned version, but some won't.  For those kitties the dried will decrease the pH which drives struvite crystal formation and help to dissolve them so they pass without incident in the urine.  Ideally though, we want to increase their water intake so their urine might not be as concentrated and also to lower the pH to a level where struvite crystals will dissolve and not form.

Bottom Line:  If in Doubt - Get it Checked Out!