All Feline Hospital

2300 S. 48th St. Ste. 3
Lincoln, NE 68506


Blocked Tomcats

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You recently brought your cat into us because he was unable to urinate.  It is very good that you brought him in when you did, as this can be fatal within 3-4 days of not being able to urinate.  Now, our goal from here on out is to get him through the next month without blocking up again, and to prevent this from happening again in the future.



Urethral blockages in male cats are most commonly caused by one of four things in this order; crystalline plugs, mucous plugs, small stones, or urethral sphincter hypertonus.

  • Crystalline plugs are almost always caused by urinary crystals, are often caused by diets that tend to alkalinize or acidify the urine, causing crystals to form.  These crystals can build up in the urethra, and eventually form a plug that keeps your cat from urinating.
  • Mucous plugs.  No one knows for sure just what causes these, but speculation includes infection, fibrin from trauma of stones or crystals, or clots from interstitial cystitis.
  • Small stones build up like any other stone in the bladder, either as a result of urine that is too alkaline or acidic, forming crystals and/or stones, or an excess of mineral build up in the urine that can precipitate into stones.  If the right size stone gets into the urethra, it can get stuck partway through since the urethra narrows in male cats.
  • Urethral sphincter hypertonus is when your cat cannot relax his urethral muscle enough to urinate.  This can happen from a variety of reasons, including chronic stress, trauma, or spinal cord disease.



Crystalline and mucous plugs

  • Diets.  These can generally be prevented by feeding diets that do not tend to alkalinize or acidify urine.
    • In some cases some cats are so sensitive that they will need to be on urinary prescription diets.
  • Water intake.  Increasing water intake will also help immensely, in keeping crystals and mucous clumps from forming.
    • This can be done by offering more fresh water, by utilizing water fountains, or by adding things to water like low salt chicken broth, tuna juice, or ice cubes to encourage fluid intake.
    • Canned foods will also provide extra water intake, but we do tend to see a few more canned foods that alkalinize urine, so please ask us for brand recommendations.

Small stones

  • If these are formed from acidic or alkaline urine, then the same steps taken to prevent crystalline and mucous plugs apply.
  • If these are formed from mineral buildups, then your cat may require specific prescription diets and lifelong medications to prevent these from forming.

Urethral sphincter hypertonus

  • This is not common, but if your cat does develop this, then there are medications to help relax the urethral sphincter.

For all of these causes, if a resolution cannot be found, and your cat continues to have problems with urethral blockages, then we may recommend a surgery called a perineal urethrostomy, which will basically make your male cat urinate like a female, and will prevent most causes of blockages.  This is however, a last resort as it can have potential complications.



Observe closely

  • For the next month, your cat will continue to be at high risk of re-blocking.  You will need to keep a close eye on your cat to make sure that he continues to urinate.
  • If you are not sure if your cat is urinating, please bring him into the clinic right away for us to palpate his bladder.

Diet change

  • Your cat will in all likelihood need to be switched to a different diet.  We will let you know our diet recommendations.


  • Antibiotics.  Please follow the label instructions and give for the full amount of time.
  • Pain medications.  Please follow label instructions and give these until they are gone.  Cats do not tend to show signs of pain, but that does not mean they don't feel it.
  • Urethral sphincter muscle relaxants.  Depending on how long your cat was blocked, we may be sending these home as some cats have a hard time urinating after being blocked for an extended length of time.
  • Urinary acidifiers.  If your cat cannot be on a urinary acidifying diet, and struvite crystals were found or suspected, we may send this home to help dissolve any remaining crystals.


  • If you are able to administer SQ fluids, and if this is not your cat's first time blocking up, or there was a very high level of crystals or mucus, then we may send your cat home on subcutaneous fluids for a month to help dilute the urine to prevent crystal or mucous plug formation.
  • If you are not able to administer SQ fluids, or if this was your cat's first time blocking up, then anything that you can do to increase his fluid intake now will help prevent him from re-blocking.  This includes having multiple bowls of fresh water available, having a water fountain, or adding items to your cat's water such as low salt chicken broth, tuna juice, or ice cubes to encourage your cat to drink more fluids.
  • If you would like for your cat to have SQ fluids but are unable to do so at home, if you can bring your cat into the clinic along with their fluids regularly, we will administer the fluids for you at no charge.


If you have any questions or concerns, please do not hesitate to contact us at All Feline Hospital at 402-467-2711 or  If you think at any time that your cat has blocked up again, it is an emergency.  If it is after hours, please call the emergency clinic at 402-489-6800.  


This handout was written by Dr. Shelley Knudsen, DVM



Printable Blocked Tomcats