Alpine Animal Hospital
Debra M. Taylor, D.V.M.
Patti A. Tuck, D.V.M. Emily A. Lewis, D.V.M.
2202 E. M-32
Gaylord, MI 49735
(989)732-6427
(989)732-4561 Fax
Email: info@alpineanimalhospitalmi.com
www.alpineanimalhospitalmi.com
Pyelonephritis
Pyelonephritis is an infection in the kidney.
Prevalence
This is a fairly common disease of cats. However, diagnosis requires an ultrasound study of the kidneys. Since only
a small percentage of veterinarians have ultrasound capabilities, it often goes undiagnosed.
Clinical Signs
In order to understand the clinical signs of this disease, it is necessary to understand some basics about kidney
function.
The kidneys’ job is not to make urine but to remove waste products from the blood. It removes waste products by
making urine. Loss of kidney function does not mean the inability to make urine. In fact, the cat’s response to
increased waste products in the blood means the kidneys work harder and make more urine than normal.
Therefore, the clinical signs of pyelonephritis often include an increase in urination and thirst. In addition, there may
be a low-grade fever, pain in the kidneys on palpation, and even signs of cystitis (bladder inflammation) as the
bacteria leave the kidneys and reside in the bladder. Many of these cats have an infection that is ongoing for several
weeks or months; they often gradually lose weight and become less active than normal.
Causes/Transmission
The bacteria that cause the kidney infection are in the blood; they are filtered out by the kidneys. They are thought
to gain access to the blood from infections or wounds in other parts of the body. The most common source of
infection is bacteria associated with tartar on the teeth. The gum tissue has a very rich blood supply so it permits
bacteria that are present near the teeth to enter the blood stream.
Diagnosis
The kidneys have a large amount of reserve tissue. It isn’t until 75% of both kidneys are destroyed that the kidneys
are no longer able to remove the waste products from the blood efficiently. Because of this, until more than 75% of
the kidney is destroyed the kidney tests are normal presumably indicating a normal kidney. While this is good for the
cat, it is very misleading to the veterinarian. Therefore, a kidney function test will usually be normal in this disease.
This test is important, however, because if elevated, it allows us to assess the extent of the damage to the kidneys.
Pyelonephritis is suspected when bacteria are found in the urine. The most common form of cystitis in cats is not
caused by bacteria so their presence in the urine is a red flag that the bacteria may have originated in the kidneys.
Pyelonephritis is also suspected in a cat with low-grade fever and kidney pain.
The diagnosis is confirmed with an ultrasound study, which permits us to look at the internal structure of the kidney.
The bacteria cause substantial damage to the kidney; this damage can be seen with ultrasound.
Treatment
The cornerstone of treatment is to identify the bacteria and to determine which antibiotics are likely to kill them. A
urine culture permits us to obtain this information. Antibiotic therapy is generally needed for 4 to 6 weeks. When
the antibiotics are completed, the urine is cultured again to be sure there are no bacteria present. If that culture is
clear, the urine is cultured again in 1-2 months to be sure there is not a relapse.
This can be a difficult disease to completely cure, so prompt urine culturing should be done any time the cat does not
seem to be doing well or signs of cystitis occur (frequent urination, blood in the urine, small amounts of urine [one
teaspoon], straining to urinate). In addition, if the cat begins to drink and urinate excessively a recheck of the urine
is indicated.
Prognosis
The prognosis is generally good if a diagnosis is made before significant damage occurs to the kidneys. However, if
kidney function is affected other measures will be needed to support the kidneys on a long-term basis.