by Miranda Levin, Betty Stephenson, DVM, and John Dillberger, DVM, Ph.D.
The Health & Genetics Committee gets several emails like this a year, so we thought it would be helpful to post this article for owners and their veterinarians, many of whom might not have dealt with cystinuria before.
Trouble peeing can be due to bladder stones. Deerhounds have two inherited conditions that could cause bladder stones: portosystemic shunt (PSS, otherwise known as liver shunt), which can cause urate stones to form; and cystinuria, which causes cystine stones to form. Your vet needs to know this information.
Liver Shunt and Urate Stones
This condition does appear in Deerhounds and can affect either sex. As it also appears in many other breeds of dogs, and even mixed breeds, your vet should be familiar with how to handle this condition.
The SDCA recommends that breeders test their puppies for liver shunt with a bile acid blood test. Your dog’s breeder should have given you a copy of your puppy’s test results when you bought your puppy. When we hear of a Deerhound—particularly a young Deerhound—with possible bladder stones, the first thing we will ask you is whether or not this dog was tested for liver shunt, as a poorly functioning liver can cause urate bladder stones to form. If your dog was not tested as a puppy, it should be tested now. The bile acid test is simply two blood draws, the first when the dog has an empty stomach and the second after it was fed a certain amount of a food and a set time interval has elapsed. It gives your vet a picture of how the liver is functioning. Even if your Deerhound was tested as a puppy, your vet still might want to do this test, as other non-hereditary conditions can cause the liver to malfunction and urate stones to form.
Cystinuria and Cystine Stones
When you have an intact (or recently neutered) male Deerhound that has bloody urine, is peeing blood, whose urine stream is reduced, or cannot pee at all, the first thing that comes into our minds is a urinary blockage caused by cystine stones.
Although cystine stones are actually very rare in the dog population as a whole, they are by far the most common cause of urinary problems in intact male Deerhounds. That’s right: female Deerhounds do not get cystinuria, and neither do neutered males, although recently neutered males can have leftover stones that formed before or right after they were neutered. In fact, cystinuria is so common, we recommend that anyone with an intact male make a habit of watching their dog pee daily in order to catch any potential problems as early as possible: any changes to a dog’s normal pee should be checked out.
Monitor Your Dog
If your dog is having a problem when he pees, be it a change in flow or the presence of blood, you should do two things:
- Make an appointment with your vet for the soonest appointment you can get.
- MONITOR YOUR DOG. Watch him pee every time he goes out.
You monitor your dog to make sure he can still pee. Why? Because, while bloody urine, reduced flow, or dribbling pee is an urgent problem for which you should get your dog to your vet as soon as you can, straining with only drops or no pee coming out at all is a LIFE-THREATENING EMERGENCY THAT CANNOT WAIT UNTIL MORNING. If only a couple of drops or nothing comes out when your dog tries to pee, you must take him to a veterinarian immediately.
While you are monitoring your dog, get some clean paper coffee filters and let your dog pee through them. Bring any with debris (which might look like grains of sand) in a clean plastic bag or container to your vet for analysis.
Diagnose the Problem
Many vets will look at you as if you have three eyes when you tell them your dog may have cystine stones. You have to understand that many vets will go their entire careers without ever seeing a cystinuria case. Urate stones due to liver shunt are more common in dogs.
Although cystine stones are the most common type in intact male Deerhounds, it is possible it could be another stone type, so it is good to have some confirmation of the problem, if you can. If the sediment trapped on the coffee filter contains cystine, urate, or some other crystals or small stones, then you have a pretty good idea of with what stone you are dealing. If not, there are several other options:
- If your dog was never tested for a liver shunt, then that can be ruled in or out with a bile acid test or other means.
- You can have a regular urinalysis done to see if urate crystals (which would indicate a liver shunt or other liver problem) or cystine crystals (which would indicate cystinuria) or some other type of crystal is found. Both urate and cystine crystals have distinct shapes when viewed under a microscope. The presence of urate or cystine crystals, combined with the change in urine, is a good indication that the dog is probably blocked with urate or cystine stones. However, a lack of crystals doesn’t necessarily mean the dog’s bladder is clear: if the dog isn’t actively forming stones, it is possible that all of the available uric acid or cystine in the urine is already bound to the stones, leaving few to no crystals floating in the urine.
- If your dog isn’t blocked so you have the luxury of time, for cystinuria, you can send a urine sample to the University of Pennsylvania for nitro-prusside (NP) testing, which is more sensitive than a regular urinalysis. However, NP testing has the same problem as a regular urinalysis: if the cystine is already bound into stones, you can get a false negative test.
- When faced with possible bladder stones, many vets’ first instinct is to x-ray, which is a great place to start, as sometimes both kinds of stones can be seen on x-ray, and x-rays are a great diagnostic tool for some of the other things that can cause bladder problems. However, both urate and cystine stones are not always seen on x-ray and are often more easily seen with ultrasound, so if nothing is seen on x-ray, the dog’s bladder (and liver, if a shunt is suspected) should be ultrasounded, preferably with a good machine run by a board-certified internist or radiologist. The big problem with cystine stones is they are not always stones. Sometimes they are sludge or gravel, and that can be hard to find. (To give you an idea of what it can look like, one lab called a vet who had submitted cystine sludge for analysis and asked why he wanted a stone analysis on a stool sample!) If you see stones, “snow” (we’ve had one vet say that the bladder looked like a snow globe), gravel, etc., then that is confirmation that the dog has stones. However, fine sand and sludge are often invisible. We have heard of several cases where nothing was seen on ultrasound, yet the dog still had cystine stones, so ultrasound is not 100% diagnostic. However, at the very least, an ultrasound can confirm or eliminate prostate gland problems—common in intact dogs—as a possible cause of the symptoms.
And yes – we realize how difficult it is to have a negative urinalysis, x-ray, and ultrasound, yet your dog still may have stones! But that does sometimes happen.
Should stones be confirmed or suspected strongly and you decide to go ahead with surgery, it is important to explain to the surgeon (especially if it’s your regular vet and it appears that the urethra is blocked) that with cystinuria, the surgery may be more involved than a standard stone removal. The problem with cystine stones is that they are extremely rough, almost spiky, and they adhere to the mucosa of the urinary tract, making it difficult to dislodge them. So if they pass from the bladder and lodge in the urethra at the base of the os penis (the bone in the terminal urethra), it is often impossible to remove them. In that situation, a urethrotomy (opening the urethra surgically to remove the stones) or a urethrostomy (making a permanent opening in the urethra when it is impossible to remove the stones) must be performed, and we’re here to tell you, those two procedures are about the bloodiest and longest recovery surgeries out there. For up to two weeks post-surgery, any excitement can cause profuse bleeding from the surgery site. This is a major reason to do surgery sooner rather than later and, if you suspect the urethra is blocked, to have a board-certified surgeon do the surgery.
Don’t forget that whoever does the surgery should be experienced in anesthetizing sighthounds. Also important is to notify the surgeon before the surgery if your dog is Factor-VII affected or a Hyperfibrinolyisis carrier or affected based on genetic testing. If your dog is the former, then your surgeon should be prepared with plasma in case a problem occurs during surgery. If your dog is the latter, then your dog will need aminocaproic or tranexamic acid post-op, and the surgeon should have some on hand in case of a problem during the surgery. If you don’t know the status of your dog for either or both of these conditions, make sure you tell the surgeon these are problems in Deerhounds and you don’t know your dog’s status.
If your vet suspects a liver shunt or other liver problem but stones need to be removed, they will explain to you the additional risks of anesthetizing a dog with a liver shunt.
If a catheter can be easily passed into the bladder, there may not be any stones/sand/sludge within the urethra. That would be good, but if stones, sludge, or gravel are present in the bladder, they still need to be surgically removed because one or more could move into the urethra at any time and cause obstruction. If the dog is still urinating and feeling ok, it might be worth waiting for the reports on the composition of any debris that was sent in or NP test results and neutering him at the same time as the cystotomy if it’s cystine.
Preventing a Recurrence
With a liver shunt, there are treatments available, ranging from managing the problem with medication to surgery to a new non-surgical treatment called percutaneous transvenous coil embolization. Some shunts are so severe they are not treatable, although if your dog didn’t have any other symptoms of a shunt before the blockage it probably doesn’t have that severe of a shunt. What treatments are recommended for your dog all depend on where and how big the shunt is. Your vet will send you to a specialist for additional testing so you can see what options are available for your dog’s liver shunt. Once the shunt is fixed, most dogs do not continue to produce urate crystals.
To date, there is only one proven method of preventing a recurrence of cystine stones in Deerhounds: neutering your dog, either surgically or chemically. Some people claim that they were able to control cystinuria with diet, but this is purely anecdotal, and the problem with anecdotal evidence is you don’t know if it was the diet or something else was going on with that dog that prevented a recurrence. Even the researchers and dog food companies don’t know whether prescription diets can prevent a recurrence or not. We encourage everyone who has had success controlling an intact dog’s cystinuria without neutering to get in touch with the SDCA Health & Genetics Committee or our cystinuria researcher Paula Henthorn. We would not be surprised if something environmental turned out to be a trigger for the disease, but we don’t know what it is yet, so the SDCA Health & Genetics Committee recommends neutering affected dogs to prevent a recurrence.
People who have no intention of breeding from or showing their dogs often have the dog neutered at the time of the cystotomy. The dog will still be at risk for a few weeks post-op, but after that will not form any more cystine stones, although struvite stones have sometimes occurred down the road in dogs that have a lot of damage to their bladder walls from cystine stones.
People who would like to collect their dog’s semen for freezing (for potential use on clear bitches after we have a genetic test) or who want the confirmation of the stone analysis before doing something as irrevocable as neutering often opt to do the neuter a couple of months after the cystotomy. If you wait, it might be prudent to have your dog ultrasounded right before the neuter in case more stones have formed.
If you do opt to wait to neuter, then we can’t emphasize enough that you should monitor your dog’s peeing every day so you can catch a potential problem as early as possible.
We are sometimes asked if stones have to be removed, or will neutering cause them to disappear. Dr. Henthorn, the researcher at Penn with whom we have been working, thinks that in theory, after neutering, any cystine stones in the bladder should probably dissolve. However, that hasn’t been confirmed with a case study, so we do not recommend it, because stones probably take weeks or months to dissolve and could potentially cause a problem before they are gone. Stones are sometimes found incidentally when a dog is getting x-rayed or ultrasounded for something else, and these owners must, in consultation with their veterinarian, weigh the risks and benefits of stone removal for that particular dog. But if your dog is already having a problem, then the stones will definitely not dissolve in time to resolve the problem and must be removed ASAP.
After surgery, no supplementation is needed. We did hear of one case where a dog was given methionine post-op, and, as methionine is the precursor of cystine, this dog continued to have problems post-neuter. Please do not give your dog methionine!
Although neutering will prevent a recurrence of cystine stones, it takes several weeks for testosterone levels to drop. Therefore, we recommend monitoring your dog’s pee for a few months after neutering, just to be on the safe side, in case more stones form in the meantime. Once this point is past, your dog will need no additional treatment, no special diet, and no supplements or medication. Your dog can go back to a completely normal life, and you no longer need to worry!
We hope this has helped you and your vet understand bladder stones in Deerhounds a bit better. If your dog has either of these conditions, we encourage you to send a blood sample to our CHIC DNA Bank if your dog has a liver shunt or, if your dog has cystinuria, to Dr. Henthorn at the University of Pennsylvania along with the stone analysis report, if stones were removed. The more dogs that participate, the more quickly we can find the genetic causes of these awful diseases.
Cover image of cystine crystals courtesy of the Minnesota Urolith Center- University of Minnesota.