Thank you for the reply.
I'm sorry your cat is experiencing these symptoms. As you know, these are signs of a problem with his urinary system, but it very likely is NOT an infection based on his age. Cats can be affected by a condition called Feline Lower Urinary Tract Disease (FLUTD) which is the name given to a set of symptoms from various causes that can affect a cat's urinary system. The causes are varied and the age of the cat partly influences the likelihood of the cause. (ie older cats are more prone to bacterial infections than younger cats). Other common causes include bladder stones, crystals, tumors, and sometimes just inflammation from an unknown cause (more common in younger cats). Unfortunately, they all can show the same symptoms, no matter the cause and all are treated a little differently. Here is a link with more information about FLUTD LINK HERE
More importantly, since crystals were noted and since you have a male cat who it is very important that you make sure he continues to be able to pass urine and doesn't become obstructed. If he is obstructed and cannot urinate, he can become very ill very quickly. Even if he is not obstructed, your vet should prescribe something to relieve his discomfort. I would switch him to wet food only to avoid a very concentrated urine that will allow the crystals to form more readily. There are prescription diets that have reduced minerals to keep crystals from forming as well. Hills c/d multicare stress LINK HERE or Royal canin urinary SO LINK HERE are excellent choices in canned or dry forms (but canned is still a better choice). Even if not feeding a prescription diet, increasing his fluid intake by switching to canned food only and perhaps providing him with a pet fountain may be the best you can do to prevent reoccurrence.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.
My posted replies are for general education only and not meant as a diagnosis. Only after a thorough veterinary examination can a diagnosis for your pet be made and specific treatments be advised or medications be prescribed.