FUS is a form of cystitis which cats suffer from. They can just get a bladder infection which makes them urinate more (they are in and out of the litter tray or garden), sometimes with some blood in the urine and some pain, however, there is a more serious form. This can happen when they suffer from more or less constant or recurrent problems. In the girls this means that they get repeat bouts of FUS but in the boys, because the tubes they urinate through (urethra) are smaller, they can get a blockage.
A blockage is life threatening, as pressure builds up in the bladder because the cat cannot wee, it can damage the kidneys, and if not treated the bladder can rupture which is usually fatal. Male cats with a blockage are very ill, reluctant to more or eat, unlike with ‘normal’ cystitis where the cats are pretty much normal in temperament. The blockage can be caused by one of two things, either there has been so much bleeding into the bladder and damage to the bladder wall that the large number of cells in the urine form a ‘plug’ in the urethra, or the cat has produced lots of small crystals in the urine which have then formed a ‘plug’, again in the urethra. Exactly the same problems occur in female cats which are uncomfortable but not life threatening.
In males the treatment for a blockage is to anaesthetise the cat and introduce a catheter to push through the blockage. the catheter is then stitched in place for a few days to enable cells or crystals in the bladder to be passed. In both sexes, a urine sample can be examined to see if the cause is cells or crystals, and if crystals, what type they are (there are several different types all treated differently).
Pain relief and antibiotics help in the short term, but in the long term we need to stop the condition recurring. This is complicated as there are many reasons why cats suffer from FUS, they include;
Stress or anxiety (this is a very complicated subject in cats!),
Treatment includes; dietary changes to stop the crystals forming or dissolve any crystals already present, anti stress medication, pain relief, drugs to protect the bladder wall. Every cat is different and treatment will differ depending on the cause, type of crystal/cell, response to treatment and how easy the cat is to give medications to.