FUS is a syndrome of cats where a sand like material is formed in the urinary tract. This material may form in the bladder and then be passed through the urethra. When passed, it may cause burning, bleeding and straining to urinate. Female cats can usually pass the crystals but male cats may become obstructed and unable to urinate. 70% of cats that are straining do not have FUS but have other bladder problems such as idiopathic interstitial cystitis or bacterial cystitis, or bladder tumors. Urinalysis, radiographs, or ultrasound may be needed to differentiate these.

FUS occurs in all breeds and ages of cats, in castrated and not castrated cats, in indoor and outdoor cats, and in those fed a variety of diets. It is one of the most serious and distressing cat diseases confronting cat owners and veterinarians.

The presence of obstruction from FUS is an EMERGENCY SITUATION and prompt treatment is essential. Treatment is directed at relieving obstruction and controlling pain and spasm. With early treatment, most FUS patients respond well; however, recurrence within a few hours to a few months is possible. Dietary changes can usually control the disease, but some cats eventually require surgery to enlarge the urethral opening. This usually prevents life threatening obstruction, but straining and passing blood may still occur.