Feline Glomerulonephritis

Overview

Inflammation of the glomeruli, the kidney's tiny filtering units responsible for the first step of blood filtration — when these become inflamed and damaged, protein that should stay in the bloodstream leaks into the urine, and over time this condition can progress to chronic kidney disease if the underlying inflammatory process isn't identified and addressed.

Symptoms

• Protein in urine (often first sign, no outward symptoms) (mild, common)
• Weight loss (moderate, common)
• Lethargy (moderate, common)
• Fluid accumulation (advanced) (severe, uncommon)

Causes

Often related to an underlying immune-mediated process, sometimes triggered by chronic infection, inflammation elsewhere in the body, or certain systemic diseases that prompt immune complexes to deposit in the glomeruli; in many cases, despite investigation, no single specific trigger is identified. Inflammation of the kidney's filtering units (glomeruli), often triggered by immune complexes depositing there in association with a chronic underlying infection, inflammatory condition, or occasionally cancer elsewhere in the body — genuinely more of a kidney manifestation of a broader underlying problem than a standalone primary kidney disease in many cases.

Risk Factors

Any chronic infectious or inflammatory condition elsewhere in the body, certain immune-mediated diseases, and in some cases an association with specific infections (like FIV) has been suggested, though the relationship isn't always straightforward or present in every case.

Transmission

Not directly transmitted or contagious — this reflects an individual cat's immune response, though an underlying infectious trigger (where identified) would have its own transmission considerations.

Incubation Period

Not applicable in the traditional sense; develops gradually as an inflammatory process within the kidney.

Disease Stages & Progression

Often insidious, developing gradually with protein loss into the urine preceding more obvious clinical symptoms; without identification and management, progressive kidney damage and chronic kidney disease can develop over time.

Early Warning Signs

Often subtle initially — may be picked up incidentally on a urinalysis showing protein in the urine (proteinuria) before other symptoms develop, which is part of why routine urinalysis as part of general senior cat screening has genuine diagnostic value.

Advanced Symptoms

Weight loss, lethargy, decreased appetite, and in more severe cases, fluid accumulation (in the abdomen or elsewhere) if protein loss becomes significant enough to affect the body's fluid balance — along with progressive signs of chronic kidney disease if the condition advances that far.

Diagnostic Methods

A urine protein-to-creatinine ratio test quantifies the degree of protein loss and is a key diagnostic and monitoring tool; kidney biopsy provides definitive characterization of the specific type of glomerular damage present, though isn't always pursued given the invasiveness involved relative to what it changes in management for many cases. Significant protein loss in urine (proteinuria) is a hallmark finding, checked via a specific urine protein-to-creatinine ratio test; kidney biopsy provides definitive diagnosis and can help identify the specific pattern of glomerular damage, though this is a more invasive step generally reserved for cases where the result would meaningfully change treatment.

Veterinary Examination Process

General assessment of body condition, hydration, and any signs of fluid accumulation; often relatively unremarkable early on, with laboratory findings driving the diagnostic process more than physical exam findings.

Recommended Lab Tests

Urine protein-to-creatinine ratio, urinalysis, blood protein levels, and standard kidney function panel; testing for underlying triggering conditions (infectious disease screening) is often pursued given how commonly an identifiable trigger is sought.

Diagnostic Imaging

Abdominal ultrasound may be used to assess kidney structure and rule out other kidney conditions, though it doesn't directly diagnose glomerulonephritis itself.

Blood Test Indicators

Low blood protein (particularly albumin) reflecting the ongoing urinary protein loss, alongside standard kidney function markers (BUN, creatinine) which may be normal early on or elevated as the condition progresses.

Biopsy / Histopathology

Kidney biopsy provides the most definitive characterization of the specific glomerular changes present, though many cases are managed based on clinical and laboratory findings without necessarily requiring biopsy.

Differential Diagnoses

Other causes of protein loss in urine, other kidney diseases, and other causes of low blood protein (including liver disease and intestinal protein loss).

Home Monitoring Guidance

Cats diagnosed with this condition benefit from periodic veterinary monitoring (urine protein levels, kidney function) rather than home-based monitoring alone, given how much the trajectory can vary between individual cats.

Veterinary Treatment Options

Identifying and treating any underlying triggering condition, where one is found, is an important first step. Medications to reduce urinary protein loss and manage blood pressure (which is often affected alongside kidney disease generally) are commonly used; a kidney-support diet, similar to that used in chronic kidney disease management, is often recommended. Treatment addresses both the kidney damage itself (blood pressure control, dietary management similar to other kidney disease, medication to reduce protein loss) and, where identifiable, the underlying trigger — searching for and treating an underlying chronic infection or inflammatory condition can sometimes improve the glomerulonephritis itself, not just the kidney symptoms in isolation.

Surgery Requirements

Not applicable.

Recovery Timeline

Variable and often managed as an ongoing, chronic condition rather than one with a defined recovery timeline, particularly if an underlying trigger isn't identified or fully resolved.

Possible Complications

Progressive chronic kidney disease, and in cases with significant protein loss, complications related to low blood protein including fluid accumulation and increased clotting risk.

Long-Term Management

Regular monitoring of urine protein levels, kidney function, and blood pressure is important on an ongoing basis, along with continued management of the underlying cause where one has been identified.

Prevention

No universal prevention given the range of possible underlying triggers; prompt treatment of chronic infections or inflammatory conditions elsewhere in the body may reduce the risk of triggering this process in some cases.

Vaccination Availability

Not applicable directly, though vaccination against relevant infectious triggers (where a specific link exists) provides indirect protection.

Prognosis

Variable — cats with an identifiable, treatable underlying trigger and good response to protein-reducing treatment can do reasonably well for a meaningful period, while progressive cases without a clear addressable trigger carry a more guarded long-term outlook tied to progression toward chronic kidney disease.

References

International Renal Interest Society (IRIS); American College of Veterinary Internal Medicine (ACVIM).

Medications Used

• Medication to reduce urinary protein loss (ACE inhibitors or related medications)
• Blood pressure medication if hypertension is present
• Treatment targeting any identified underlying trigger
• Anti-inflammatory or immune-modulating medication in select cases

Estimated Treatment Cost by Country

Frequently Asked Questions