Pyelonephritis
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Pyelonephritis is bacterial infection and inflammation of one or both kidneys. Bacteria most often reach the kidneys by travelling upward from the lower urinary tract, although infection can occasionally spread through the bloodstream. Cats with chronic kidney disease, diabetes, urinary tract abnormalities, stones or reduced immune defence may be at greater risk.
Signs vary considerably. Some cats develop fever, lethargy, poor appetite, vomiting, dehydration or pain around the kidneys. Others show increased thirst and urination or lower urinary signs such as frequent urination and blood in the urine. Cats can also have surprisingly subtle disease, particularly when infection occurs alongside chronic kidney disease.
Kidney infection matters because untreated bacteria can damage renal tissue, enter the bloodstream or lead to recurrent urinary infection. It can also cause an acute worsening of kidney values in a cat with previously stable CKD.
The sample is ideally collected in a way that minimises contamination.
Pyelonephritis is treatable, but treatment must reach bacteria within kidney tissue and continue for an appropriate period. Follow-up is important because clinical signs can improve before infection is completely eliminated. Recurrence should prompt investigation for an underlying structural or medical reason.
Because cats may not show the classic combination of fever and obvious urinary pain seen in other species, pyelonephritis can be overlooked. In a cat with unexplained kidney deterioration, especially one with a previous urinary infection or structural urinary disease, infection of the kidneys remains an important and treatable possibility.
Early detection is most important in cats with known risk factors such as chronic kidney disease, diabetes, urinary stones or repeated urinary infections. Whenever possible, urine is collected by cystocentesis so the sample is less likely to be contaminated. Blood pressure and hydration may also be assessed.
Screening & Early Detection
A sudden increase in thirst, worsening kidney values, fever, vomiting, poor appetite or unexplained lethargy in these cats should prompt consideration of kidney infection.
Urinalysis can show white blood cells, bacteria or blood, but culture is the key diagnostic test. Culture identifies the organism and provides antibiotic susceptibility information.
Blood tests assess kidney values, electrolytes and the inflammatory response. Ultrasound is useful when the veterinarian needs to look for kidney enlargement, changes in the renal pelvis, ureteral obstruction, stones or other abnormalities that might allow infection to persist.
There is no need to screen every healthy cat routinely for pyelonephritis. Testing is targeted to compatible signs or increased risk. Cats being treated for confirmed kidney infection require follow-up, often including repeat urine culture, because disappearance of fever or urinary signs does not prove that bacteria have been eradicated.
Diagnosis requires more than simply seeing bacteria on a routine urine sample. A urine culture is used to confirm infection and identify which antibiotics are likely to work. Blood tests assess kidney function, hydration and systemic illness. Ultrasound may reveal changes in the kidneys, ureters or bladder and can identify stones or obstruction that make infection harder to clear.
Treatment & Management
Treatment uses an antibiotic that reaches effective concentrations in kidney tissue and is appropriate for the organism identified on culture. Therapy is usually longer than for a simple lower urinary infection, and the exact duration is guided by clinical response, culture results and the veterinarian’s assessment.
Cats that are dehydrated, vomiting or systemically unwell may need hospitalisation with intravenous fluids, anti-nausea medication, pain relief and nutritional support. Kidney function and electrolytes are monitored during treatment. If imaging identifies a ureteral obstruction, stone or structural problem, that issue may also need to be treated before infection can be fully controlled.
Antibiotics should not be stopped early simply because the cat appears better. Inadequate treatment can lead to relapse and may encourage resistant bacteria. Follow-up urine culture is often recommended after treatment to confirm clearance, particularly in cats with chronic kidney disease or recurrent infection.
Long-term management focuses on the underlying risk factor. Good control of diabetes, appropriate management of stones and monitoring of CKD can reduce recurrence. A cat that deteriorates again after treatment should be reassessed promptly rather than automatically receiving the same antibiotic without a new culture.
Breeds or species affected
Abyssinian
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American Bobtail
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American Curl
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American Shorthair
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American Wirehair
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Arabian Mau
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Aegean
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Australian Mist
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Balinese
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Bengal
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Birman
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Bombay
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British Longhair
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British Shorthair
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Burmese
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Burmilla
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Chartreux
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Chausie
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Colorpoint Shorthair
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Cornish Rex
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Cymric
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Devon Rex
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Domestic Longhair
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Domestic Medium Hair
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Domestic Shorthair
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Donskoy
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Egyptian Mau
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European Shorthair
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Exotic Shorthair
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Havana Brown
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Highlander
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Himalayan
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Japanese Bobtail
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Khao Manee
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Korat
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Kurilian Bobtail
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LaPerm
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Lykoi
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Maine Coon
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Manx
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Minuet
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Minskin
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Munchkin
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Nebelung
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Norwegian Forest Cat
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Ocicat
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Oriental Longhair
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Oriental Shorthair
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Persian
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Peterbald
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Pixiebob
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RagaMuffin
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Ragdoll
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Russian Blue
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Savannah
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Scottish Fold
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Scottish Straight
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Selkirk Rex
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Siamese
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Siberian
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Singapura
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Snowshoe
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Somali
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Sphynx
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Thai
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Tonkinese
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Toybob
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Toyger
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Turkish Angora
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Turkish Van
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Bambino
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Cheetoh
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Dwelf
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Elf Cat
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Genetta
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Kinkalow
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Lambkin
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Serengeti
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Skookum
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Ukrainian Levkoy
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