Glomerulonephritis in dogs – symptoms, tests and treatment

Overview

Inflammation is one type of glomerular disease

The nephron is the kidney's functional unit, comprising a capillary cluster and a tubule that processes urine further.

The glomerulus is a cluster of capillaries involved in filtering blood. A healthy filter retains most blood proteins in the body. In glomerular diseases, the filter's structure or function changes.

Immune complex glomerulonephritis is one of the common glomerular diseases in dogs. Others include glomerulosclerosis, or glomerular scarring, and amyloidosis. Distinguishing these from inflammation affects treatment choice. In selected biopsies taken for suspected glomerular disease, around 50% showed immune complex glomerulonephritis. This proportion does not describe disease prevalence among all dogs.

Causes

An immune reaction damages the filter

An immune complex consists of an antigen and an antibody recognising it. Complexes formed in the bloodstream can accumulate in the glomerulus. They can also form when an antigen trapped in the glomerular wall meets an antibody arriving from the circulation. These deposits trigger a local inflammatory response.

Damage can thicken the basement membrane and narrow glomerular capillaries. Persistent changes can cause glomerular scarring and loss of function. Basement membrane damage allows proteins into the urine. Severe or chronic proteinuria can also damage kidney tubules.

An underlying disease may sustain the reaction

Glomerulonephritis can be associated with infection, inflammation or a tumour elsewhere in the body. Possible infections include Lyme disease, ehrlichiosis and leishmaniosis. Systemic lupus and immune-mediated polyarthritis have also been associated with it. However, the initiating cause of many glomerular diseases is unknown. Disease arising without a known cause is called idiopathic.

Risk factors

Glomerular diseases are most commonly diagnosed in middle-aged and older dogs. Inherited glomerular diseases can appear earlier. They have been described in breeds including Bernese Mountain Dogs, Cocker Spaniels, Dobermanns, Samoyeds and Soft-Coated Wheaten Terriers. These inherited diseases are not all the same immune complex-mediated inflammation.

Glomerulonephritis has also been found among immune-mediated diseases in Kooikerhondjes. A persistent infection or immune disease elsewhere in the body is a reason to consider possible kidney involvement too. High blood pressure, in turn, can increase glomerular protein leakage.

In immune diseases of Kooikerhondjes, external or internal factors as well as genetics can influence disease onset.

Typical symptoms

Initially, the only finding may be persistent protein loss without inflammatory cells in the urine. Possible observations at home include:

• Tiredness or being quieter than usual.
• Reduced appetite.
• Weight loss or muscle wasting.
• Increased drinking and urination.
• Swelling of the legs, underside of the chest or abdomen.
• Vomiting or diarrhoea associated with kidney failure.

Swelling can develop when blood albumin falls because of protein loss. The number of signs does not directly reflect how much protein is lost into urine: severe proteinuria can occur before kidney filtration clearly declines.

With swelling related to protein loss, pressing with a finger may leave a visible dent in the skin for a short time.

Complications and consequences

Kidney function and protein loss

Glomerular disease can cause chronic kidney disease or sometimes acute kidney injury. Tubular damage reduces the ability to concentrate urine. Waste products in the blood may subsequently rise.

Nephrotic syndrome describes the combination of severe protein loss, low blood albumin, high cholesterol and fluid accumulation in tissues or body cavities. Blood clots associated with glomerular disease have been found in 12–21% of studied patients. Blood pressure can rise at any stage of chronic kidney disease.

The disease type determines the outlook

Nephrotic syndrome and severe azotaemia are associated with a poor outlook. Azotaemia means the accumulation in blood of nitrogen compounds normally removed by the kidneys. Some dogs have progressive disease that shortens life, while others can live a normal lifespan with appropriate treatment. Identifying a treatable underlying cause can improve the outcome.

Diagnosis at the vet

Urine, blood and blood pressure

Urine testing confirms persistent renal proteinuria. Findings such as blood, inflammatory cells and bacteria in urine are considered first, as they may indicate a lower urinary tract cause. UPC is the urine protein-to-creatinine ratio. A value above 2 strongly suggests glomerular protein loss but does not confirm the exact inflammation type.

A canine UPC below 0.2 is classified as non-proteinuric. The borderline range is 0.2–0.5. A value above 0.5 is classified as proteinuric. Ideally, classification uses at least 2 samples over at least 2 weeks.

Blood tests assess kidney function and the consequences of protein loss. High blood creatinine is not required for glomerular disease to be diagnosed. Blood pressure is measured to detect concurrent hypertension.

Normal urine concentration does not exclude glomerular disease, as protein loss can begin before concentrating ability declines. If chronic kidney disease is diagnosed, its stage is assessed using blood creatinine and SDMA. Your dog must be stable and appropriately hydrated for staging.

Looking for the underlying cause

The physical examination also considers the eyes, mouth and skin. Infection testing is selected according to where your dog lives and their travel history. In severe or progressive disease, chest and abdominal imaging can help identify a tumour. Possible links between other diseases and the kidney findings are investigated at the same time.

What does a kidney biopsy show?

A tissue sample is needed to identify the precise type of glomerular disease. Biopsy is considered particularly for severe or worsening disease that does not respond to standard treatment to reduce protein loss. It is not an automatic test for every dog with proteinuria. Untreated high blood pressure and clotting disorders increase bleeding risk and prevent sampling.

Other reasons to consider biopsy include chronic kidney disease in a young dog or enlarged kidneys. Sampling may be considered in chronic kidney disease stages 1–3 but is generally not recommended in stage 4.

Assessing glomeruli requires electron microscopy and immunofluorescence testing as well as routine light microscopy. The sample is collected and prepared carefully for these examinations. Interpretation requires a pathologist experienced in kidney pathology. This can distinguish inflammatory disease from amyloid deposits, for example.

Treatment

Treating the underlying cause and protein loss

Your vet treats any identified underlying disease. At the same time, protein leakage through the kidneys is reduced. Blocking the RAAS system to reduce protein loss lowers pressure within the glomerulus. Persistent renal proteinuria needs treatment when UPC exceeds 0.5, regardless of kidney disease stage.

An angiotensin receptor blocker, or ARB, is used. Your dog receives an appropriate veterinary renal diet. An ACE inhibitor may also form part of treatment in selected patients. Combining an ACE inhibitor and an ARB requires particular care and close monitoring. Dehydration is corrected before these medicines are started.

High blood pressure is treated according to the dog's overall kidney condition. Antithrombotic medication reduces the clot risk associated with severe protein loss. A renal diet can reduce protein leakage even before azotaemic kidney failure develops.

Dietary changes may also include adding omega-3 fatty acids.

Neither albumin concentration nor the amount of protein loss alone reliably predicts an individual dog's clot risk.

Blood pressure treatment in dogs with kidney disease generally aims to reduce systolic pressure below 160 mmHg to lower organ damage risk. Advanced kidney failure may also require treatment for dehydration, nausea, loss of appetite and anaemia.

When is immunosuppressive treatment needed?

Immunosuppressive treatment is appropriate for severe or progressive disease where biopsy confirms immune complex glomerulonephritis. In some severe cases, it is considered without biopsy confirmation after careful assessment of benefits and risks. Treatment response and medication adverse effects are monitored closely. This decision is separate from standard treatment for all dogs losing protein into urine.

Immunosuppressive treatment may use mycophenolate or ciclosporin, for example, according to your vet's choice.

Treatment response and ongoing monitoring

The aim is to reduce protein loss as much as possible without causing harm. If a UPC below 0.5 cannot be achieved, a 50% reduction from the initial value is the target for many dogs with primary glomerular disease. A good response includes stable creatinine and falling UPC. A rise in previously low blood albumin supports a good response.

Potassium, blood pressure and any deterioration in kidney function are also monitored during medication. With an ACE inhibitor, safety tests are usually performed 1–2 weeks after starting or changing treatment. Maintenance treatment may continue for life unless the underlying cause resolves.

The protein loss response measured by UPC is usually assessed around 1 month after treatment starts.

Prevention

Identifying an infection or other treatable underlying cause associated with glomerulonephritis forms part of managing kidney disease. No single general home measure prevents inherited or immune-mediated disease.

Some Kooikerhondje breeding guidelines recommend against breeding dogs with immune disease. They advise avoiding pairings where both dogs have similar immune diseases in close relatives. No genetic test is available to rule out glomerulonephritis in Kooikerhondjes. Medicines potentially harmful to the kidneys are withdrawn from a dog with kidney disease following veterinary assessment.

Dogs with kidney disease must always have fresh drinking water available to prevent dehydration.

Important for dog owners

What information is needed for monitoring?

Bring previous UPC results, kidney values, albumin and blood pressure readings. Record weight and appetite, and changes in drinking, urination and swelling. Bring a medication list and details of travel, previous infections or immune diseases. Travel history affects the choice of infection tests.

Ask whether your dog has suspected glomerular disease or biopsy-confirmed glomerulonephritis. Establish what the sample showed and whether it changes treatment. Alongside agreeing monitoring tests, find out what to do if your dog becomes dehydrated, vomits or stops drinking. In a dehydrated dog, an ACE inhibitor or ARB can markedly reduce kidney filtration. Contact an emergency vet immediately for difficulty breathing or sudden collapse.

Frequently asked questions

Is glomerulonephritis always a bacterial infection?

Glomerulonephritis affects the capillary clusters involved in filtering blood. Glomerular disease can result from an immune reaction rather than simply bacterial infection. Tests therefore investigate the type of kidney damage and any other disease so treatment addresses the actual cause, rather than relying on the name alone.

Can a dog have glomerulonephritis with normal kidney blood values?

Yes. Severe protein loss can occur without azotaemia, or nitrogen compounds accumulating in blood. Proteinuria may be the only early finding. Urine testing therefore complements blood tests, and persistent urinary protein is investigated even in an otherwise well dog.

Does every dog need a kidney biopsy?

Biopsy is not suitable for every situation. It is considered particularly for severe or progressive disease that does not respond to standard treatment. Untreated high blood pressure and clotting disorders prevent sampling because of bleeding risk. The decision depends on what the sample could change in treatment.

Is glomerulonephritis always treated with immunosuppressive medicine?

Immunosuppressive medication is used selectively, particularly for severe or progressive biopsy-confirmed immune complex disease. Standard proteinuria treatment also includes medication to lower glomerular pressure and dietary management. The same medication is therefore not automatically suitable for every glomerular disease.

How long can a dog live with glomerulonephritis?

Some glomerular diseases progress and shorten life, but some dogs live a normal lifespan with appropriate treatment. Severe azotaemia and nephrotic syndrome worsen the outlook. Your vet assesses your dog's situation using the disease type, kidney function and response seen during follow-up.