Just another few websites that I suspect you would also recommend:
American Association of Feline Practitioners http://www.catvets.com/ Lots of great info including various Guidelines written by some of the top experts ... e.g. Vaccination Guidelines (currently in the process of being updated), Retrovirus Guidelines, Senior Care Guidelines, Life Stages Guidelines, Bartonella, etc.
Veterinary Partner http://www.veterinarypartner.com/ A great site for pet owners run by VIN (Veterinary Information Network ... which is for vets only) which gives good info on many pet health issues and medications.
American College of Veterinary Internal Medicine (ACVIM) http://www.acvim.org Besides being able to look for board certified specialists in a specific geographical area, the site has lots of good info including a section on "Consensus Statement" on various health issues.
In this case, many of the researchers and specialists would disagree with you about early age neutering. There have been a number of studies that have not shown any connection between early neuter and smaller urethras. Here are a couple quotes:
However, several scientific studies have now shown these concerns are unwarranted. For example, it is has been shown that early-age altering of cats: "022 does not cause stunted growth in cats (University of Florida study, 1996). "022 does not contribute to increased surgical and anesthetic risks or post-surgical complication rates (University of Texas studies, 1997 and 2000). "022 does not cause serious behaviour problems in cats (University of Cornell study, 2004, and Mercer University study, 2001). "022 does not contribute to feline lower urinary tract disease (University of Minnesota study, 1996, and University of Texas study, 2000). "022 does not cause obesity (University of Minnesota study, 1996). In fact, a large-scale study from Cornell University of over 1,600 cats—adopted from a humane society in New York State and followed for up to 11 years—showed early-age altered cats had less risk of certain health problems including gingivitis, asthma and abscesses—than cats altered at traditional ages.
"Despite numerous vehemently declared anecdotes of an increase in the incidence of urethral obstruction in male cats castrated when young, numerous studies (35,132,135) have failed to detect a correlation between gonadectomy of cats at any age and a decrease in diameter of the urethra or an increase in incidence of FLUTD, with or without urethral obstruction."
"The American Association of Feline Practitioners supports neutering early in life as a safe and effective method of decreasing cat overpopulation, and one which confers long-term medical and behavioral benefits to the individual cat."
If you know of a study that shows that early neutered males have smaller urethras, I'd be interested in a reference.
As I'm sure you know, there are two primary types of crystals that cats get (struvite & calcium oxalate) one caused by too high pH and the other by too low. I think many of the "crystal" diets now aim to get the pH in the optimal range that will help prevent either type of crystal ... rather than just trying to raise or lower the pH to prevent one type of crystal.
Another option for a carrier is to get one with an entry door in the top as well. That is what I use. It is large enough, and with the help of gravity, I can just drop my kitty in from the top. It also makes it easier to get her out at the vet's.
I took a look at the Pet-to-Human Weight Translator ... for cats. It might be better for dogs since they are broken down into breeds and the general size is more uniform within a particular breed. But the cat seems to have ALL cats lumped together. Cats come in different sizes ... i.e. bone structures ... as well. Ten pounds on a Korat, Russian Blue, Devon or Cornish Rex, Burmese, etc is going to be a lot different than 10 pounds on a Maine Coon, RagaMuffin, Ragdoll, Siberian, etc.
The BCS can help determine if a cat is a good weight for the size frame it has. Maybe someone can break down the "Pet-to-Human Weight Translator" for cats as they did for dogs. Meanwhile, it may mislead some people to think a cat with the frame of a Maine Coon is somehow overweight at 12 lbs when it might actually be underweight for it's frame.
I'm glad your cat is doing well now with just a diet change. Many cats have food sensitivities and feeding a good diet is always helpful.
I'm not a vet and have no credentials ... but my own kitten had a bout of cystitis and I like to listen to talks given at veterinary conferences by some of the leading experts. So, I'll try to share a little of what I "think" I have learned.
As I'm sure you know, cystitis is an "inflammation" of the bladder. In young cats under 10, it is rarely (only about 1%) caused by an "infection". So, antibiotics are generally not helpful, though many vets prescribe them, "just in case". In older cats that are prone to more dilute urine, infections are much more common.
The vets who didn't know the cause would be correct in many cases of cystitis ... hence it is often called "Feline Idiopathic Cystitis" (FIC) which means cystitis of unknown origin.
Studies have shown that many cats with FIC will get better in 5-7 days ... with or without any medication. I know we owners often want a pill or something to "fix it" but that often isn't the case with cystitis.
However, recent research has identified a link between cystitis and how a cat responds to stress. They are not sure if cystitis is primarily a bladder problem that causes neurological signs or if it is a neurological problem that manifests in bladder problems. Cats that are susceptible to cystitis respond physically in a different way to stress than cats not prone to cystitis. Episodes of cystitis often occur during or after episodes of stress ... even their picking up our stress. Dr Larry Adams of Purdue, in a talk on cystitis commented that when he began vet school, his own cat had regular episodes of cystitis about four times a year. By his senior year, his own stress level dropped and his cat's episodes of cystitis dropped to twice a year and later once a year.
So, modifying the environment and doing what we can to reduce a cat's stress can be very helpful with cystitis. The Indoor Cat Initiative at Ohio State Univ, headed by Dr Tony Buffington, has much info on reducing stress in the cat's environment. They have developed what they call "MEMO" (multimodal environmental modification) with ways of reducing stress and have shown that it helps reduce the episodes of cystitis in many cats. The Indoor Cat Initiative can be found at: http://www.vet.ohio-state.edu/indoorcat
While a high quality diet (no grains, high and good quality animal protein, low carbohydrates, pH balanced, etc) is always beneficial, nearly every study has found that the most important factor is adding more water into the diet. One way of doing that is using a canned food diet and even adding water to it.
It makes sense. When a cat doesn't get enough water, the urine becomes very concentrated and is more likely to irritate the bladder. Since the urine sits in the bladder longer waiting for it to fill, it has more chance to cause irritation and for crystals or stones to form. I don't know if they have found the exact mechanism, but increasing water intake always helps.
While some vets try prescribing antibiotics or steroids or NSAIDs or Glucosamine/chondroitin, etc ... Dr Larry Adams said placebo controlled double-blinded studies with each of them have shown no difference in resolving an episode ... i.e. most cats get over it in 5-7 days with or without treatment.
However, he does recommend giving pain medication since it is thought to be painful (and certainly is for human women) and suggests a narcotic like Buprenorphine (aka Buprenex).
I have a number of friends with cats that have had cystitis episodes. It seems that it is more common now. I don't know if that is partially from feeding more dry food, or increased stress or just genetic susceptibility. It is certainly a frustrating disease for all.