American Fancy Rat & Mouse Association

This article is from the Winter 2000 AFRMA Rat & Mouse Tales news-magazine.


Kidney Stones vs. Kidney/Bladder Infections

By Carmen Jane Booth, D.V.M.

5-week-old Tailless Rat with Bladder Stones

Helen Pembrook, Sky Valley, CA
Q The subject at hand is a little Siamese Tailless male born 4-9-99. He was purchased at the May AFRMA show on Saturday 5-15-99. He passed health check in the morning and seemed healthy when I picked him up at about 2:00. At 4:30 or so he was rattling terribly to the point where I could feel it with my hand and hear the rattle 2 feet away. He seemed better that evening and the rattle was gone on Sunday, so I assumed his problems were due to stress. On Monday he showed drastic signs of weight loss: his hips were greatly pronounced and his sides sunken in. When I examined him, I felt a hard long lump in the center of his belly. My initial thought was an intestinal or bladder blockage or maybe a tumor or cancer, but I was not familiar with rat anatomy at the time so I wasn’t sure. I noticed that when I watched him, he would eat a little of the treats I gave him but would not drink anything. On Tuesday his belly was bloated and the long lump was larger. On Tuesday early afternoon he died. The necropsy showed that there was a lot of fluid throughout the abdominal cavity and that the bladder was blown up like a balloon to about the size of a grape, 1 inch long by ½ inch wide. All of the other organs appeared to have good color and be healthy except the kidneys which were a little bit gray. We assume this is probably the result of the urine being so backed up. Upon further examination, it was discovered that there were 7–10 small grain-of-sand-sized kidney or bladder stones in the bladder after it was emptied of fluid. The assumption thus far is that a stone blocked the urethra so that the animal could no longer urinate.

A This is very interesting. There are a variety of causes of urolithiasis in animals. With the animal being so young, I wonder about genetic defects linked to the taillessness. The best way to try and understand what happened would be to have sent the kidneys and bladder for histology and have the crystals examined to determine the exact type. Crystals can be formed in the kidneys or in the bladder. Diet, disease, and hydration can all contribute to their formation. Knowing what type of crystal(s) are present can help in determining the underlying cause.

Another thought is that in animals that are genetically Tailless, there are often problems with urinary or bowel movement control. It is likely that the crystals plugged the urethra, but bladder atony could have contributed. I would also have submitted the urethra for histology. Actually, I would have had the entire rat examined for histology in cases such as these.

Following are some additional questions and answers regarding kidney stones vs. kidney/bladder infections.

Case scenario: 3 male rats in one cage all less than 1 year old; blood in urine is noticed on one of the solid metal shelves in the cage and it is pinpointed as to which rat is doing this, rat goes to vet, vet thinks the problem is cancer, vet takes a sample of the rat’s urine and sends in for a pathology report, report comes back NOT cancer — just an infection, rat acts fine throughout this whole ordeal, owner treats rat for infection, blood in urine goes away, all rats in cage now happy and healthy.

Details: all rats are fed lab blocks with an occasional piece of washed vegetable or fruit. They are on CareFRESH™ bedding, get cleaned once a week (the cage is very large for 3), get bottled water to drink, and played with often.

Q How do rats get kidney stones?

A The cause is varied and can be from substances in the diet, kidney infections, etc. The kidneys are giant filters, and in the process of excreting urine (water, urea, and dissolved salts — normal function of the kidney) sometimes precipitates form. Think of rock candy which is formed by a concentrated solution of sugar in water. The precipitates form when the urine pH is high, water content low, and precipitate content high. Cats get this most commonly from diets high in Mg or ash..

Q How do rats get kidney/bladder infections?

A In most cases, urinary tract infections are caused by bacteria ascending from the urethra to the bladder and then to the kidneys themselves. Some cases are caused by sepsis (bacteria throughout the body) or in males with a prostatitis (infection of the prostate). Animals with chronic kidney stone production are more prone to chronic urinary tract infections because of the chronic irritation of the lining of the urinary tract.

Q Can what rats eat/not eat cause a problem?

A There is no specific dietary factor indicated in rodents that I am aware of.

Q How do you treat the problem(s)?

A For simple first-time infections, I use a general oral antibiotic for 2–3 weeks. In protracted cases or repeat cases, I do a urine culture and sensitivity and choose the suggested antibiotic. No specific antibiotic is given because this is not something anyone should treat themselves and depends on the situation.

Q What are the symptoms in the rat?

A In any species, the most common symptoms are increased frequency urination (and water consumption), pain or straining on urination, blood in urine. Incontinence is a common symptom in dogs and cats. In cases where there are kidney or bladder stones or fine granular precipitate, the urethra may become blocked and then it is a life threatening situation if the blockage is not removed. This is most common in male cats because of the small diameter of the tip of the urethra.

Q Is the behavior different in the rat depending on the problem (i.e. does the rat act fine for a kidney/bladder infection vs. the rat acts sick/off with a kidney stone?)

A No, it really depends on the severity of the situation irregardless if there are stones/precipitates or solely urinary tract infection.

Q Is it more common in one sex?

A I have seen this more frequently in male than female rats.
You also have to remember that as rats age, they get a condition of the kidneys called “Chronic Progressive Nephropathy” and is associated with a high protein diet. This disease results in inflammation, fibrosis, and destruction of the filtration apparatus of the kidneys (glomerulosclerosis).

Q What kind of tests does a vet run to determine what is wrong with the rat?

A A urinalysis is the usual test with cytologic examination of centrifuged urine to look for bacteria, crystals, blood, tumor cells, etc. For discrete stones, a radiograph or ultrasound is sometimes used if stones are suspected and none are palpable.

Q What are the chances of it being cancer rather than just an infection/stone?

A No statistics are known. Cancer in any species becomes more suspect in an older animal.

Q Many have asked if Tylan would be used to treat a kidney infection or other general infections?

A No, the strains of bacteria that infect the respiratory tract are different from those that infect the urinary tract (in most cases) and usually require specific antibiotics.

Q What about if someone sees blood in the urine in a couple of their male rats once in a while. Should they take the rat to the vet, keep an eye on the rat for any change in behavior, treat themselves, or something else?

A Anyone who sees blood in the urine of their animals should take them to the veterinarian, even if there are no other symptoms. Blood in the urine is never normal and means that there is bleeding somewhere there shouldn’t be bleeding. *

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Updated March 20, 2014