HELP please - at wits end with urethritis and sludge in bun

(sorry if some of you might have seen this plea before elsewhere but I've lost track of who lurks where and I need all the help I can get!)

I will try and keep this brief as I need IDEAS and HELP!

I am at my wits end with Teasal. He is 7 years old neutered male house/patio/lawn/everywhere bun.

About 3-4 years ago he was first noted as having the occasional sludge bladder. A year ago this was bad enough to be catheretred under GA and have it removed. It was then kept in control by maunual expressing every month or so and Frusol when it seemed to build up, and avoiding high calcium things.
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A month ago he had to have the whole thing cathetered out again - it took ages apparently and was solid. After that he went onto Septrin for 10 days, as well as metacam for a week. We also changed to a totally pellet free diet (before that we were on Burgess Excell for years and lately Science Selective).

He is now fed hay ad lib (meadow hay), and weeds basically (avoiding the high calcium ones) supplemented with carrots and the odd bit of fruit. We provide one bowl of just water and one of water with fruit juice (apple) mixed to try and get him to drink.. He has loads of exercise, is the right weight, perfect health otherwise, happy (except when he gets this), and active.

Yesterday I noticed him straining to wee again (less than one month after he was last cathetered), and took him to the vets. Sure enough its urethritis (although she cannot feel any sludge this time). There is no blood in the urine but he keeps just straining and spotting and his uretha is swollen and irritated.

We are now on metacam for a month, Frusol for a month, and Baytril for 10 days (last time it was Septrin) to try and 'break the cycle' (as the vet put it).

But I cannot understand WHY he keeps getting either sludge or (as this time) urethritis even when there is no sludge.

I asked for bloods and urine analysis but she said to do it in 2 weeks time after the meds.

Today he looks even worse and is just squatting every few seconds it seems like.

Can anyone think of anything we mght have missed??? (he has had Lapizole for EC and kidneys were fine when last x-rayed just a month ago).

Could it be something lacking in the diet?? Or is the water with fruit juice perhaps the wrong pH?? Is there some kind of magic balance we should be looking for with some other vitamin or mineral?

I am at my wits end - and so is he I think.

We have just oral syringed him 30mls of water t at least give him something to pee with but there MUST be a solution to this??? HELP

(PS I have 12 rabbits in all and Teasal is the only one with this problem).

Oh gawd

If his urethra is going into spasm then Diazepam may help.

Has abx therapy been based on a culture/sensitivity test ? Although in my experience Baytril always seems to be a good abx for a UTI

The meadow hay, does it have a lot of Alfalfa mixed into it or is it mainly timothy?

Metacam wont stop Urethral spasms. The spasms make him feel like he needs to wee even when he doesn't and he'll 'strain' and it'll hurt.
Diazepam is a muscle relaxant (aswell as a sedative) an it might help break the spasm-strain-pain-spasm cycle.

After he had the last catheterisation did he receive diuresis for a few days ? -ie subcutaneous fluids at 100ml/kg. This may need to be done on an 'every few days' basis longterm.
I have a Doe whose bladder needed expressing daily to remove sludge and she also required diuresis 4 times a week. Strangely enough now she is nearly 9 the problem has resolved ........

Catheterisation can actually cause urethral muscle spasms so a Benzodiazepam (eg Diazepam) should be given after the proceedure.

Apparently a lack of a certain gut bacteria -Oxalobacter- can mean that calcium oxolate in the diet is not broken down and consequently uroliths/sludge occurs. In humans with this condition a probiotic -Oxolobacter formigenes- can be given to increase the oxolate reducing bacteria in the gut.
I dont know if there is a suitable preparation to give to Rabbits

Some Vets suggest giving Potassium Citrate orally to reduce the concentration of calcium in the urine.