Are kidney crystals found only in male cats or do females have them too?

First of all, we need to separate the ideas of kidney stones and urinary bladder stones.  The kidneys and the bladder are two different parts of the urinary system.  Usually, when you hear someone talking about stones and the urinary system, they are referring to stones in the bladder.  Kidney stones just don't happen with the frequency of bladder stones.  That being said, kidney stones do happen and when they do, they can occur in both sexes.

Bladder stones also occur in both sexes, for dogs as well as cats.  They happen for various reasons...type of food being eaten, urinary infections, certain metabolic problems, certain genetic disorders.  Some of these stones can acquire a fair size and almost always require surgery to remove them.  

You may be referring to the "grit" type substance that occurs in the urinary bladder of the male cat, then becomes lodged in the urethra to produce a blockage of urine flow.  Female cats can produce this same type of grit, but the diameter of their urethra is wider and the urethra is a shorter distance to the outside...so, the grit hardly ever causes a problem for them.

Hopefully, this clears that up for you.

Helpful Buckeye