Pyelonephritis (Kidney Infection) in Cats

Overview of Feline Pyelonephritis

Pyelonephritis is an inflammation of the kidney. We generally refer to pyelonephritis in cats as a bacterial infection of upper urinary tract including any part of the kidney.

Below is an overview of Pyelonephritis in Cats followed by in-depth detailed information about the diagnosis and treatment of this condition.

General Causes of Kidney Infections in Cats

Ascending urinary tract infections (originating from the lower urinary tract) caused by bacteria
Hematogenous (from the bloodstream) seeding of infection is much less common

What to Watch For

• Excessive drinking and urinating
• Abdominal or back pain
• Painful urination
• Frequent urination
• Straining to urinate
• Bloody urinations
• Malodorous urinations
• Vomiting
• Diarrhea
• Lethargy
• Loss of appetite

Diagnosis of Pyelonephritis in Cats

Baseline tests to include a complete blood count, biochemical profile, and urinalysis are recommended in all patients. Although often within normal limits, there may be changes consistent with kidney failure or urinary tract infection.

Additional tests may include:

• A bacterial urine culture to check for associated infection
• Abdominal radiographs (X-rays) to rule out calculi (stones) and other diseases that might mimic pyelonephritis
• Abdominal ultrasound to visualize the urinary tract (in particular, the renal pelvises) and other abdominal structures
• Excretory urography (a dye study of the upper urinary tract including the kidneys and ureters)

Treatment of Pyelonephritis in Cats

It is most important to determine whether the patient’s condition warrants admission to the hospital for treatment or treatment at home as an outpatient. Treatment may include:

• Dietary modification in those patients with concurrent renal (kidney) failure or urinary calculi
• Antibiotic treatment, based on urine culture and sensitivity
• Fluid therapy

Home Care

Administer all medication and diet as directed by your veterinarian. Return for follow up as recommended and notify your veterinarian if any change is noted in your cat’s condition.

In-depth Information on Pyelonephritis in Cats

Pyelonephritis is an inflammation of the kidney, and is most often due to a bacterial infection that has made its way from the lower urinary tract (urinary bladder) to the kidney. There may be factors that enhance the susceptibility to infection such as congenital abnormalities, metabolic disorders or systemic immunosuppression; however, no underlying disorders need exist.

The clinical signs associated with pyelonephritis may be mild, or may even go unnoticed, although pyelonephritis can lead to kidney failure, sepsis (infection throughout the bloodstream) and even death, if not addressed. Depending on the specific case, certain diagnostics and therapeutics are usually recommended and tailored to each individual. Several diseases or disorders can present similarly and need to be differentiated from pyelonephritis. These include:

• Urolithiasis (stones) anywhere throughout the urinary tract
• Lower urinary tract infection
• Chronic kidney failure
• Bacterial prostatitis (inflammation of the prostate)
• Metritis (inflammation of the uterus)
• Other causes of fever and painful abdomen such as pancreatitis (inflammation of the pancreas) or peritonitis (inflammation of the abdominal cavity), as a percentage of animals with pyelonephritis present for abdominal pain
• Other causes of increased thirst and increased urination include hyperadrenocorticism (Cushing’s disease), diabetes mellitus, kidney disease and liver disease

Diagnosis In-depth

Certain diagnostic tests must be performed to diagnose pyelonephritis definitively and to exclude other disease processes that may cause similar symptoms. A complete history, description of clinical signs, and thorough physical examination are all an important part of obtaining a presumptive (probable) diagnosis of pyelonephritis. In addition, the following tests are recommended:

• A complete blood count (CBC) may be within normal limits, but an elevated white blood cell count may be present.
• A biochemical profile may be within normal limits, but it may reveal elevations in kidney enzymes or electrolyte abnormalities.
• A urinalysis may reveal blood, white blood cells, protein or bacteria in the urine. The absence of any or all of these does not rule out pyelonephritis.
• A bacterial urine culture is performed to confirm a urinary tract infection, however, may be negative in some cases of pyelonephritis.
• Abdominal radiographs (X-rays) are an important part of any baseline work-up. Although they may be within normal limits, they may reveal changes in kidney size, urinary calculi, or help to rule out other diseases and causes of the patients’ clinical signs.
• Abdominal ultrasound is recommended in most cases suspect of having pyelonephritis. It is helpful in evaluating the kidney and potentially differentiating between upper and lower urinary tract infection. There are characteristic changes seen within the renal pelvis (inside of the kidney) that are consistent with pyelonephritis. Kidneys may be enlarged in acute (sudden onset) cases and small in chronic (long-term) cases. Ultrasound is also helpful in evaluating for the presence of stones throughout the urinary tract. It is a noninvasive procedure that often necessitates the expertise of a specialist and/or referral hospital.

Your veterinarian may recommend additional tests to exclude or diagnose concurrent conditions. These tests are not always necessary in every case, although they may be of benefit in certain individuals, and are selected on a case-by-case basis. These include:

• Excretory urography. This intravenous dye study “lights up” the upper urinary tract (kidneys and ureters) and is helpful in documenting pyelonephritis. It also helps detect stones in the urinary tract, and may identify other abnormalities, such as ectopic ureters. An ectopic ureter is a congenital abnormality in which the ureter (the tube that drains the kidney into the bladder) joins the bladder in an abnormal position, causing a host of clinical signs, most commonly, urinary incontinence (leaking) and recurrent infections.
• A bacterial culture of the renal pelvis. With the guidance of abdominal ultrasound, this test may be particularly important in the patient who has a negative urine culture obtained from the bladder.
• Kidney biopsy. In a few cases, this invasive procedure may be of benefit in diagnosing pyelonephritis and may necessitate exploratory surgery in certain cases.

Therapy In-depth

• Stable patients can be treated as outpatients as long as they are monitored closely. With appropriate therapy, most patients do quite well and can expect to see a full recovery. In more chronic cases, response to therapy can take longer and occasionally response may be poor. It is important that you follow all recommendations by your veterinarian very closely, and that you address any questions or concerns that arise during the treatment protocol immediately.
• Correction of any underlying predisposing factors such as ectopic ureters, urolithiasis or prostatitis is imperative to treatment.
• Antibiotic therapy selected on the basis of bacterial culture and sensitivity of the urine or renal tissue is the most important part of therapy. It is important to administer all medication as directed by your veterinarian. Usually, a treatment protocol of at least four to six weeks is indicated.
• Dietary modification is recommended in animals with concurrent kidney failure or urolithiasis.
• Hospitalization, intravenous fluid therapy, and antibiotic administration may be necessary in certain cases of pyelonephritis.
• Surgical intervention may be necessary in cases of pyelonephritis that are associated with or secondary to urinary calculi.

Follow-up Care for Cats with Pyelonephritis

Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your cat does not rapidly improve.

Unresolved pyelonephritis may lead to kidney failure; therefore, diagnostic follow-up is important to document the resolution of pyelonephritis. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your cat.

Repeat the urine culture and urinalysis approximately seven to ten days into treatment, and one to two weeks after the entire course of treatment has been completed. It is important to obtain urine cultures every two to three months until three negative cultures are obtained. If at any point the culture is positive, an additional course of antibiotics, often longer than the original course, is generally recommended. Infection may persist in some animals despite appropriate, repeated courses of antibiotics.