Deagle113
Citizen of Zooville
I figured this has come up often enough here it warranted a post. Here's everything you wanted to know about UTIs. Keep in mind that I am one perspective, and one veterinarian, and the stuff here is meant to inform, and not to treat. Always follow the advice of your clinical veterinarian when it comes to treating things and diagnosing them!
To orient ourselves to urinary tract infections, we should first go over a bit of anatomy. The entire urinary tract consists of the kidneys, ureters (the tubes that carry urine to the bladder for storage), the urinary bladder, the male prostate (which encircles the bladder neck, at least in canines), and the urethra that conducts urine outside the body.
Canine example
A urinary tract infection could involve any of these areas, though when most of us talk about a “UTI,” we mean “bladder infection” specifically. Because these infections are localized inside the bladder, there are rarely signs of infection in other animal body systems: no fever, no appetite loss, and no change in the blood tests for various values.
Side note: If the infection does ascend all the way to the kidneys, then we may well find other signs and lab work changes. While a kidney infection is technically also a urinary tract infection, we use the term pyelonephritis to describe it.
For our felines, It is also important to note in this discussion that the term UTI is frequently erroneously used to refer to feline idiopathic cystitis, which is a common inflammatory condition of the feline bladder affecting young adult cats, and not a bladder infection at all.
Signs and Symptoms
The bladder is a mostly sterile area of the body. Bacteria and other organisms, when they aren’t just passing through, gain entry and establish growth inside–this is when infection occurs and symptoms result, such as
There are two major tests that can be performed on a urine sample as we work towards a diagnosis:
Urinalysis
A urinalysis examines the chemical properties of the urine sample–pH, specific gravity (a measure of concentration), and amount of protein or other biochemicals. It also includes a visual inspection of the urine sediment–usually by our amazing nurses–to look for crystals, cells, or bacteria. Running this is an excellent first step to determine if additional culture or diagnostics are needed, and it’s an excellent screen for our companions.
Urine Culture (and Sensitivity)
This is the only test that can definitely confirm a urinary tract infection. For this one, we take a small sample of urine and transfer it to a plate filled with delicious bacteria food to grow them, like planting unknown seeds in a soil to figure out what plants grow!
Once we know the species, we can figure out which are known to cause disease and work out the best antibiotics that they may be susceptible to. Unlike urinalysis, urine culture results require at least a couple of days for the bacteria to grow. .
Sample Collection
There are three major ways urine can be collected for a sample to examine or culture–free catch, catheter, and cystocentesis. Some folks insist on a fourth–directly from a surface–but I think the quality of this one is so low as to be non-usable. In all cases, the less contaminated the urine by environmental bacteria, the better, as this allows us to determine what is actually residing in the bladder.
A free catch sample is obtained by catching urine mid-air as it is passed. The urine sample may be contaminated by the bacteria of the lower urinary tract but will not be contaminated by the floor or other environmental surface. This one can be a bit of a challenge, but is usually what we task you with when we send you home to collect a sample.
With the catheter method, we pass a small tube into the bladder and remove some urine. This is obviously not the most comfortable method for any animal patient, though the procedure is fairly quick. Though it is still possible for contamination to occur, this sample is a lot better than the free-catch one.
The ideal collection method is cystocentesis: we use a fairly long needle and guide it with an ultrasound probe directly into the bladder. In this way, an uncontaminated sample is collected directly from the bladder. This is the best sample to culture and is the most accurate representation of bladder flora!
Treatment for Simple (Sporadic) Infection
The simplest type of UTI is called a sporadic infection, which means the patient has had less than three UTIs in the preceding 12 months. We diagnosed it based on the urinalysis and patient history, culture it to get a list of effective antibiotics, and treat it. UTI symptoms should be obviously improved within 48 hours of starting the correct antibiotic. There is evidence that antibiotics aren’t even needed for these urinary tract infections and they resolve on their own quite rapidly.
How long treatment should continue is controversial. The traditional duration is 10-14 days of antibiotics. As resistance rises in the world’s bacteria (meaning all our drugs are getting less and less effective) the veterinary community has been researching shorter or alternate durations of treatment – so go with what your vet decides.
Treatment for Recurrent Infection
Though your vet may recommend post-treatment urinalysis or culture, the most important aspect determining that we resolved the UTI is whether or not the patient still has symptoms. If they do, we classify it as a recurrent infection, defined as more than three UTIs in the preceding 12 months or two or more UTIs in the preceding 6 months.
This is a much more complicated scenario. Culture results are especially important here as they will help determine if a UTI simply did not resolve with prior treatment or if a whole new infection with a different bacterial species has started. Now we start pulling out Imaging of the urinary tract to look for complicating urinary factors like bladder stones, polyps, kidney involvement that may be preventing resolution. This can be a long road, and post-treatment cultures for any bacteria become a lot more important.
I’ve listed the most common complicating factors below:
Kidney Infection (Pyelonephritis)
If a patient's immune system is compromised due to age or other factors, the infection in the bladder may ascend into the kidneys, where it can cause kidney failure and a more serious infection. There is currently no good test to determine whether or not a kidney is infected, though there might be hints on the lab work, or you may notice additional symptoms like a urinary tract infection in combination with more body wide signs like a fever or pain in the area of the kidneys. Diagnostically, ultrasound can help with imaging, and there are specialized x-ray tests that can be run as well. Traditionally, antibiotics are given for a long time (four to six weeks), Though we have amended our practices recently to follow current human guidelines of a 14-day course of treatment.
Bladder Stones
Stones in the bladder can cause infection, and infection can cause stones. I could write an entire post about stones and am happy to do so if needed.
Bladder Tumors
Bladder tumors, with or without infection, often create symptoms similar to those of a severe bladder infection. The tip off to look for a tumor is that infection and/or symptoms do not clear up with an appropriate antibiotic course, urine is bloody, and there are no bladder stones on x-rays. The most common bladder tumor is a transitional cell carcinoma.
Prostatitis
The prostate gland is located at the neck of the bladder and due to its glandular nature, infection in the bladder readily spreads to the prostate, where the folded architecture is particularly protective against antibiotic penetration and easily harbors infection. It is nearly impossible to clear the prostate of the bacterial infection without neutering (which shrinks down the organ to a much smaller and more manageable size), though attempts can be made. Because of this and a few additional factors, including the formation of mini abscesses in the organ itself, bacterial prostatitis is very complex to manage and treat.
Vaginal Stricture
For females, sometimes recurrence of infection is due to a vaginal stricture–a small narrowing in the vagina that creates a ledge for bacteria to colonize. I always include vaginal exams on my full physicals, but not everyone does, and this can be missed. Most strictures can be broken down manually, though pain control and sedation are necessary.
Urachal Diverticulum
In early embryonic life, urine is removed from the body via the umbilical cord. A structure called the urachus exits off the top of the fetal bladder and enters the umbilical cord to dump urine into the mother's bloodstream for removal by her kidneys. After birth, the urachus usually degenerates, but sometimes a small protrusion still exists on the top of the bladder. This section can be a tiny safe harbor for bacteria to re-colonize the bladder after treatment, and will be a constant issue until the urachal diverticulum is surgically removed.
To orient ourselves to urinary tract infections, we should first go over a bit of anatomy. The entire urinary tract consists of the kidneys, ureters (the tubes that carry urine to the bladder for storage), the urinary bladder, the male prostate (which encircles the bladder neck, at least in canines), and the urethra that conducts urine outside the body.
Canine example
A urinary tract infection could involve any of these areas, though when most of us talk about a “UTI,” we mean “bladder infection” specifically. Because these infections are localized inside the bladder, there are rarely signs of infection in other animal body systems: no fever, no appetite loss, and no change in the blood tests for various values.
Side note: If the infection does ascend all the way to the kidneys, then we may well find other signs and lab work changes. While a kidney infection is technically also a urinary tract infection, we use the term pyelonephritis to describe it.
For our felines, It is also important to note in this discussion that the term UTI is frequently erroneously used to refer to feline idiopathic cystitis, which is a common inflammatory condition of the feline bladder affecting young adult cats, and not a bladder infection at all.
Signs and Symptoms
The bladder is a mostly sterile area of the body. Bacteria and other organisms, when they aren’t just passing through, gain entry and establish growth inside–this is when infection occurs and symptoms result, such as
- Excessive water consumption (though there is some controversy about this and I’m not going to weigh in on either side).
- Urinating only very small amounts at a time.
- Urinating frequently and in multiple spots.
- An inability to hold urine for the normal amount of time/apparent incontinence.
- Bloody urine (though an infection must either involve a special organism, a bladder stone, a bladder tumor or be particularly severe to make urine red to the naked eye).
There are two major tests that can be performed on a urine sample as we work towards a diagnosis:
Urinalysis
A urinalysis examines the chemical properties of the urine sample–pH, specific gravity (a measure of concentration), and amount of protein or other biochemicals. It also includes a visual inspection of the urine sediment–usually by our amazing nurses–to look for crystals, cells, or bacteria. Running this is an excellent first step to determine if additional culture or diagnostics are needed, and it’s an excellent screen for our companions.
Urine Culture (and Sensitivity)
This is the only test that can definitely confirm a urinary tract infection. For this one, we take a small sample of urine and transfer it to a plate filled with delicious bacteria food to grow them, like planting unknown seeds in a soil to figure out what plants grow!
Once we know the species, we can figure out which are known to cause disease and work out the best antibiotics that they may be susceptible to. Unlike urinalysis, urine culture results require at least a couple of days for the bacteria to grow. .
Sample Collection
There are three major ways urine can be collected for a sample to examine or culture–free catch, catheter, and cystocentesis. Some folks insist on a fourth–directly from a surface–but I think the quality of this one is so low as to be non-usable. In all cases, the less contaminated the urine by environmental bacteria, the better, as this allows us to determine what is actually residing in the bladder.
A free catch sample is obtained by catching urine mid-air as it is passed. The urine sample may be contaminated by the bacteria of the lower urinary tract but will not be contaminated by the floor or other environmental surface. This one can be a bit of a challenge, but is usually what we task you with when we send you home to collect a sample.
With the catheter method, we pass a small tube into the bladder and remove some urine. This is obviously not the most comfortable method for any animal patient, though the procedure is fairly quick. Though it is still possible for contamination to occur, this sample is a lot better than the free-catch one.
The ideal collection method is cystocentesis: we use a fairly long needle and guide it with an ultrasound probe directly into the bladder. In this way, an uncontaminated sample is collected directly from the bladder. This is the best sample to culture and is the most accurate representation of bladder flora!
Treatment for Simple (Sporadic) Infection
The simplest type of UTI is called a sporadic infection, which means the patient has had less than three UTIs in the preceding 12 months. We diagnosed it based on the urinalysis and patient history, culture it to get a list of effective antibiotics, and treat it. UTI symptoms should be obviously improved within 48 hours of starting the correct antibiotic. There is evidence that antibiotics aren’t even needed for these urinary tract infections and they resolve on their own quite rapidly.
How long treatment should continue is controversial. The traditional duration is 10-14 days of antibiotics. As resistance rises in the world’s bacteria (meaning all our drugs are getting less and less effective) the veterinary community has been researching shorter or alternate durations of treatment – so go with what your vet decides.
Treatment for Recurrent Infection
Though your vet may recommend post-treatment urinalysis or culture, the most important aspect determining that we resolved the UTI is whether or not the patient still has symptoms. If they do, we classify it as a recurrent infection, defined as more than three UTIs in the preceding 12 months or two or more UTIs in the preceding 6 months.
This is a much more complicated scenario. Culture results are especially important here as they will help determine if a UTI simply did not resolve with prior treatment or if a whole new infection with a different bacterial species has started. Now we start pulling out Imaging of the urinary tract to look for complicating urinary factors like bladder stones, polyps, kidney involvement that may be preventing resolution. This can be a long road, and post-treatment cultures for any bacteria become a lot more important.
I’ve listed the most common complicating factors below:
Kidney Infection (Pyelonephritis)
If a patient's immune system is compromised due to age or other factors, the infection in the bladder may ascend into the kidneys, where it can cause kidney failure and a more serious infection. There is currently no good test to determine whether or not a kidney is infected, though there might be hints on the lab work, or you may notice additional symptoms like a urinary tract infection in combination with more body wide signs like a fever or pain in the area of the kidneys. Diagnostically, ultrasound can help with imaging, and there are specialized x-ray tests that can be run as well. Traditionally, antibiotics are given for a long time (four to six weeks), Though we have amended our practices recently to follow current human guidelines of a 14-day course of treatment.
Bladder Stones
Stones in the bladder can cause infection, and infection can cause stones. I could write an entire post about stones and am happy to do so if needed.
Bladder Tumors
Bladder tumors, with or without infection, often create symptoms similar to those of a severe bladder infection. The tip off to look for a tumor is that infection and/or symptoms do not clear up with an appropriate antibiotic course, urine is bloody, and there are no bladder stones on x-rays. The most common bladder tumor is a transitional cell carcinoma.
Prostatitis
The prostate gland is located at the neck of the bladder and due to its glandular nature, infection in the bladder readily spreads to the prostate, where the folded architecture is particularly protective against antibiotic penetration and easily harbors infection. It is nearly impossible to clear the prostate of the bacterial infection without neutering (which shrinks down the organ to a much smaller and more manageable size), though attempts can be made. Because of this and a few additional factors, including the formation of mini abscesses in the organ itself, bacterial prostatitis is very complex to manage and treat.
Vaginal Stricture
For females, sometimes recurrence of infection is due to a vaginal stricture–a small narrowing in the vagina that creates a ledge for bacteria to colonize. I always include vaginal exams on my full physicals, but not everyone does, and this can be missed. Most strictures can be broken down manually, though pain control and sedation are necessary.
Urachal Diverticulum
In early embryonic life, urine is removed from the body via the umbilical cord. A structure called the urachus exits off the top of the fetal bladder and enters the umbilical cord to dump urine into the mother's bloodstream for removal by her kidneys. After birth, the urachus usually degenerates, but sometimes a small protrusion still exists on the top of the bladder. This section can be a tiny safe harbor for bacteria to re-colonize the bladder after treatment, and will be a constant issue until the urachal diverticulum is surgically removed.