What is pyelonephritis?

Pyelonephritis is a bacterial infection of the kidney and renal pelvis. Common signs include lethargy, vomiting, and abnormal urination. A vet examination and urine culture are needed to confirm the diagnosis and guide treatment.

How long is the typical antibiotic course?

The length of treatment depends on the severity of infection and culture results, typically ranging from 2 to 6 weeks. Always complete the full course as directed and return for a urine recheck.

What can I do to prepare at home first?

Track changes in appetite, drinking, and urination; take photos or videos of any abnormal behaviour; and bring a fresh urine sample and a current medication list to the clinic.

When is a urine culture needed?

Your vet will recommend a urine culture if there is blood in the urine, recurrent infections, or if initial treatment is not producing improvement. It identifies the causative bacteria and tests antibiotic sensitivity to guide appropriate drug selection.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Pyelonephritis in Dogs & Cats: Lethargy, Urinary Testing & Treatment Guide [2025]

Bacterial kidney infection requiring prolonged antibiotic treatment

Take 1 minute to check the symptoms first

Last updated: 2026/01/06

Pethealthmap Editorial Team

Sources: ISCAID, WSAVA, National Taiwan University Veterinary Hospital

When to See a Vet

Seek emergency care immediately

•Severe and persistent weakness, inability to stand, or loss of consciousness
•Repeated vomiting with inability to eat, or signs of severe dehydration
•Difficulty urinating or visibly heavy blood in the urine

Schedule a clinic visit soon (within 24–72 hours)

•Noticeably decreased appetite lasting more than one day without improvement
•Significant change in water intake or urination frequency
•Intermittent blood in urine or abnormal urine color

01What symptoms indicate something is wrong?

Pyelonephritis commonly causes changes in energy, digestion, and urination — owners should monitor daily behaviour and toileting habits.

Noticeably low energy or reduced activity
Reduced appetite or refusing to eat
Repeated or increased vomiting
Diarrhoea or changes in stool consistency
More frequent urination or signs of straining to urinate
Noticeably increased water intake or excessive thirst
If any of the above changes appear, seek a vet appointment promptly

02How to assess symptoms at home: key observations and emergency criteria

Recording these specific observations at home before your appointment helps the vet assess your pet's condition more quickly.

Note the time symptoms first appeared and how they have progressed
Track daily changes in appetite and water intake
Record the number of vomiting episodes and the consistency and colour of vomit
Log urination frequency and whether straining or loss of bladder control is present
Observe stool consistency and watch for blood in faeces or unusual odour
Use your phone to record videos of abnormal urination or discomfort
Bring your notes and videos to the clinic for the vet to review

03How will the vet make a diagnosis? Common diagnostic tests

At the clinic, the vet will typically order the following tests to confirm infection, assess kidney function, and identify the underlying cause.

Complete blood count (CBC)

to assess for systemic inflammation

Blood biochemistry panel

to evaluate kidney values and electrolyte balance

Urinalysis

including urine sediment, specific gravity, and protein

Urine culture and sensitivity

to identify the causative bacteria and guide antibiotic selection

Abdominal ultrasound

to examine the kidneys and bladder for structural abnormalities

X-rays

to check for urinary stones or pelvic abnormalities

Referral to a urology or internal medicine specialist may be recommended for further evaluation

04Treatment and aftercare: medications, diet adjustments, and home care

Treatment centres on antibiotics chosen based on culture results, with the course adjusted according to clinical response and regular follow-up.

Administer antibiotics as prescribed, based on urine culture results
Complete the full course as directed and schedule follow-up appointments
Follow-up visits typically include repeat urinalysis or a second urine culture
Dietary adjustments may be advised to reduce excessive salt or protein load on the kidneys
Monitor at home for changes in body temperature, appetite, and urination
Recurrent infections warrant referral to a urology specialist or additional imaging

05What to prepare before the appointment: helping the vet pinpoint the cause quickly

Note when symptoms started and how they have changed over time

Prepare a record of drinking and urination habits over the past three days

If vomiting or blood in stool has occurred, take photos to document it

List all current medications and supplements your pet is taking

If possible, bring a fresh urine sample to the clinic for testing

Mention when booking that urine culture or ultrasound may be needed

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.