Urinary problem in 25 year old gelding

Question
We have owned our 25 year old Thoroughbred gelding for over 15 years.  He has been mostly healthy except for Lyme Disease several years ago.  He has been something of a hard keeper, prone to weight loss and picky eating until 2 weeks ago when we moved him to a new barn with a routine and management style more like the one where he thrived years ago.  He is now eating everything they put in front of him, has gained weight in all the right places and is putting on good muscle in the neck and topline.
All was fine until yesterday when we arrived at the barn to find him in distress, irritable, tossing his head, and mildly aggressive.  He is normally gentle so we knew something was wrong and suspected colic even though he was passing manure.
The vet arrived and upon exam found a very distended bladder.  She administered Lasix and got only a narrow stream in response.  The catheter emptied the bladder and the urine was clear until near the end of the process when we got some cloudy, milky urine.  There was no sign of crystals.
He was immediately relieved and once the sedation wore off he ate, drank and passed urine and manure.
This morning, no urine from the overnight period.  During the day, he seemed comfortable but again his urine stream was somewhat thin when we got some at all.  He was happy being saddled and did fine on a one hour trail ride at the walk with another horse and rider.
This evening he ate his dinner and drank normally, but still somewhat less than the usual stale amount.
We are worried about stones (the former barn manager had put him on alfalfa when he didn't like the hay she used)as well as infection, nurological problems (but all the other reflexes and functions seem fine)and just need another opinion.  Our vet was not able to come to a diagnosis and her partner will be coming back to have a look.
Any insights you may offer would be much appreciated, as well as suggestions about treatment.  Can we "scope" the urethra and bladder as in human care?  What can be done at our home barn without a traumatic trip to the nearest referral center 2 hours away?
Thank you for any help you a may be able to offer.

Answer
Maureen:

Yes the bladder can be scoped fairly easily at home, but you need a vet to do it that knows what they're looking at. I understand the signs you have seen but Im not sure that you have a definitive problem yet. It doesnt sound like any diagnostics have really been run. I Strongly suggest a simple urinalysis to look at cell types, look for bacteria (ponly if its a sterile catheter sample) and evaluate sediment. the cloudy urine you saw with the catheter can be absolutely normal. Also, routine blood work is indicated to evaluate kidney function and for any evidence of other problems that could look like this too. The fact that the urinary stream has been thin is in no way a specific indication of a problem. However, if the horse is straining to urinate, urinating frequently in small amounts and/or you see frank blood in the urine, there could be a real urinary problem. However, you cannot see the abnormal things in urine with the naked eye sometimes. Thats why you need a urinalysis done. In addition to focus on the urinary system, I strongly suggest that a good COMPLETE physical examination be done with all blood work in order to make sure you catch any other possible problems either related to the urinary tract or completely unrelated- especially in a 25 year old horse. Also, If everything seems ok, it may be that there is no major problem- but the compete examination, blood work and urinalysis is where i would start. In my eyes, I dont think you are at the point where you need to immediately scope the bladder yet. Good luck and stay in touch. Ill be here if you have any other questions or if I can provide any further guidance.